Xpantastic!

Hi everyone, my xpander seems to fail the VCO tune test randomly!some
voices fail during one test and pass on the next! there is no
cosistancy on the voices that fail,it can be any one of them!Some
times(rarely) the vco test passes! I have the same problem sometimes
with the Resonance and VCF but not as often!
I have totally rebuilt the power supply,changed the battery and output
bypass capacitors!All currents measure right so this is not a voltage
supply problem!
The only other part I can think of is the DAC or maybe the Timer?
Any thoughts?
Takis.

Hello takisdamaschis,

When you say output capacitors, are you talking about the small 2.2uF
Cx49 at the edge of the voice board? There is one for each voice.
There is also one of these at the output of each VCO feeding the VCF
If these go you can have tuning problems. Also, try resetting the 
software.( hold sown clear and turn power On)

Karl


--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:

>
> Hi everyone, my xpander seems to fail the VCO tune test randomly!some
> voices fail during one test and pass on the next! there is no
> cosistancy on the voices that fail,it can be any one of them!Some
> times(rarely) the vco test passes! I have the same problem sometimes
> with the Resonance and VCF but not as often!
> I have totally rebuilt the power supply,changed the battery and output
> bypass capacitors!All currents measure right so this is not a voltage
> supply problem!
> The only other part I can think of is the DAC or maybe the Timer?
> Any thoughts?
> Takis.
>

Hi Carl,
yes I replaced all six Cx49 capacitors!
What number are the other ones you're refering to?Are they also 2.2uF?
Many thanks,Takis.

 
--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:

>
> Hello takisdamaschis,
> 
> When you say output capacitors, are you talking about the small 2.2uF
> Cx49 at the edge of the voice board? There is one for each voice.
> There is also one of these at the output of each VCO feeding the VCF
> If these go you can have tuning problems. Also, try resetting the 
> software.( hold sown clear and turn power On)
> 
> Karl
> 
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi everyone, my xpander seems to fail the VCO tune test randomly!some
> > voices fail during one test and pass on the next! there is no
> > cosistancy on the voices that fail,it can be any one of them!Some
> > times(rarely) the vco test passes! I have the same problem sometimes
> > with the Resonance and VCF but not as often!
> > I have totally rebuilt the power supply,changed the battery and output
> > bypass capacitors!All currents measure right so this is not a voltage
> > supply problem!
> > The only other part I can think of is the DAC or maybe the Timer?
> > Any thoughts?
> > Takis.
> >
>

Hi Takis,
The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for each 
voice respectivly. And Yes they are the same 2.2uF 50V Make sure they 
are 50V rating. and correct polarity (You probobly knew that)
But before you replace those, try this.You are saying you are having 
problems with all the voices right?
This points to the main DAC/Tuming circuit as you have already 
guessed.

I would look closely at:
 U811           The DAC        
 U816,U805      Multiplexer    4051
 U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
 U814           Analog Switch  4053 

Any of these parts failing could cause tuning problems like you 
describe.
Now, before you replace them carfully pull them from the sockets and 
re-seat them. Sometimes corrosion on the socket/chip lead can cause 
a "not to good" connection. Also before I replaced them I would 
reflow the solder on the bottom of the board, as bad solder joints 
could also cause this.
If this does not work replace em. All except the DAC are readily 
available. I would wait till you replaced the other chips before you 
went searching for this DAC to see if any others are the cause. If 
one of the chips have failed, I would bet on the mux or analog switch.
It would not hurt to replace the capacitors I mentioned above, as 
they are probobly on their way out anyway.  

Let Me Know How It Goes

Karl
 

--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:
>
> Hi Carl,
> yes I replaced all six Cx49 capacitors!
> What number are the other ones you're refering to?Are they also 
2.2uF?
> Many thanks,Takis.
> 
>  
> --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> >
> > Hello takisdamaschis,
> > 
> > When you say output capacitors, are you talking about the small 
2.2uF
> > Cx49 at the edge of the voice board? There is one for each voice.
> > There is also one of these at the output of each VCO feeding the 
VCF
> > If these go you can have tuning problems. Also, try resetting the 
> > software.( hold sown clear and turn power On)
> > 
> > Karl
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > <takisdamaschis@> wrote:
> > >
> > > Hi everyone, my xpander seems to fail the VCO tune test 
randomly!some
> > > voices fail during one test and pass on the next! there is no
> > > cosistancy on the voices that fail,it can be any one of them!
Some
> > > times(rarely) the vco test passes! I have the same problem 
sometimes
> > > with the Resonance and VCF but not as often!
> > > I have totally rebuilt the power supply,changed the battery and 
output
> > > bypass capacitors!All currents measure right so this is not a 
voltage
> > > supply problem!
> > > The only other part I can think of is the DAC or maybe the 
Timer?

> > > Any thoughts?
> > > Takis.
> > >
> >
>

Wow Karl,
are you sure you haven't designed this synth?
You definately have amazing knowledge on it's design!
I will replace all parts you mentioned except for the DAC wich I will
at least reseat!
In return for your help let me know if you're ever in dire need of a
fluorescent display for your own use ofcourse!
I was smart enough about 10 years ago to buy a couple NOC ones spare
just in case and I know they are impossible to find!
I'll let you know how it goes!
Thanks,Takis!

--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:

>
> Hi Takis,
> The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for each 
> voice respectivly. And Yes they are the same 2.2uF 50V Make sure they 
> are 50V rating. and correct polarity (You probobly knew that)
> But before you replace those, try this.You are saying you are having 
> problems with all the voices right?
> This points to the main DAC/Tuming circuit as you have already 
> guessed.
> 
> I would look closely at:
>  U811           The DAC        
>  U816,U805      Multiplexer    4051
>  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
>  U814           Analog Switch  4053 
> 
> Any of these parts failing could cause tuning problems like you 
> describe.
> Now, before you replace them carfully pull them from the sockets and 
> re-seat them. Sometimes corrosion on the socket/chip lead can cause 
> a "not to good" connection. Also before I replaced them I would 
> reflow the solder on the bottom of the board, as bad solder joints 
> could also cause this.
> If this does not work replace em. All except the DAC are readily 
> available. I would wait till you replaced the other chips before you 
> went searching for this DAC to see if any others are the cause. If 
> one of the chips have failed, I would bet on the mux or analog switch.
> It would not hurt to replace the capacitors I mentioned above, as 
> they are probobly on their way out anyway.  
> 
> Let Me Know How It Goes
> 
> Karl
>  
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi Carl,
> > yes I replaced all six Cx49 capacitors!
> > What number are the other ones you're refering to?Are they also 
> 2.2uF?
> > Many thanks,Takis.
> > 
> >  
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > > Hello takisdamaschis,
> > > 
> > > When you say output capacitors, are you talking about the small 
> 2.2uF
> > > Cx49 at the edge of the voice board? There is one for each voice.
> > > There is also one of these at the output of each VCO feeding the 
> VCF
> > > If these go you can have tuning problems. Also, try resetting the 
> > > software.( hold sown clear and turn power On)
> > > 
> > > Karl
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > Hi everyone, my xpander seems to fail the VCO tune test 
> randomly!some
> > > > voices fail during one test and pass on the next! there is no
> > > > cosistancy on the voices that fail,it can be any one of them!
> Some
> > > > times(rarely) the vco test passes! I have the same problem 
> sometimes
> > > > with the Resonance and VCF but not as often!
> > > > I have totally rebuilt the power supply,changed the battery and 
> output
> > > > bypass capacitors!All currents measure right so this is not a 
> voltage
> > > > supply problem!
> > > > The only other part I can think of is the DAC or maybe the 
> Timer?
> > > > Any thoughts?
> > > > Takis.
> > > >
> > >
> >
>

Hi Karl,
I have gone and replaced all parts you suggested, re-seated the dac
and went over all solders!
No improvement, I keep getting the same problem!
I also noticed that I get 3.79V at one of the pins of U815 instead of
4.0V(+/- .05V) as the service manual points out!
Anyway the good news is that I found a NOS dac ($150) which I will try
out as soon as it gets in(in a few days I hope).
I'll let you know!
Thanks,Takis.


--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:

>
> Hi Takis,
> The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for each 
> voice respectivly. And Yes they are the same 2.2uF 50V Make sure they 
> are 50V rating. and correct polarity (You probobly knew that)
> But before you replace those, try this.You are saying you are having 
> problems with all the voices right?
> This points to the main DAC/Tuming circuit as you have already 
> guessed.
> 
> I would look closely at:
>  U811           The DAC        
>  U816,U805      Multiplexer    4051
>  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
>  U814           Analog Switch  4053 
> 
> Any of these parts failing could cause tuning problems like you 
> describe.
> Now, before you replace them carfully pull them from the sockets and 
> re-seat them. Sometimes corrosion on the socket/chip lead can cause 
> a "not to good" connection. Also before I replaced them I would 
> reflow the solder on the bottom of the board, as bad solder joints 
> could also cause this.
> If this does not work replace em. All except the DAC are readily 
> available. I would wait till you replaced the other chips before you 
> went searching for this DAC to see if any others are the cause. If 
> one of the chips have failed, I would bet on the mux or analog switch.
> It would not hurt to replace the capacitors I mentioned above, as 
> they are probobly on their way out anyway.  
> 
> Let Me Know How It Goes
> 
> Karl
>  
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi Carl,
> > yes I replaced all six Cx49 capacitors!
> > What number are the other ones you're refering to?Are they also 
> 2.2uF?
> > Many thanks,Takis.
> > 
> >  
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > > Hello takisdamaschis,
> > > 
> > > When you say output capacitors, are you talking about the small 
> 2.2uF
> > > Cx49 at the edge of the voice board? There is one for each voice.
> > > There is also one of these at the output of each VCO feeding the 
> VCF
> > > If these go you can have tuning problems. Also, try resetting the 
> > > software.( hold sown clear and turn power On)
> > > 
> > > Karl
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > Hi everyone, my xpander seems to fail the VCO tune test 
> randomly!some
> > > > voices fail during one test and pass on the next! there is no
> > > > cosistancy on the voices that fail,it can be any one of them!
> Some
> > > > times(rarely) the vco test passes! I have the same problem 
> sometimes
> > > > with the Resonance and VCF but not as often!
> > > > I have totally rebuilt the power supply,changed the battery and 
> output
> > > > bypass capacitors!All currents measure right so this is not a 
> voltage
> > > > supply problem!
> > > > The only other part I can think of is the DAC or maybe the 
> Timer?
> > > > Any thoughts?
> > > > Takis.
> > > >
> > >
> >
>

Hi Takis,
> I also noticed that I get 3.79V at one of the pins of U815 instead 
> of 4.0V(+/- .05V) as the service manual points out!

Okay, lets look at D805, A zener diode which provides the reference
for the DAC.Measure this with a good voltmeter, it should be 6.9V. 
Again, try reflowing the solder around this part and the ref circuit. 
If you have a service 
manual, Look at the circuit around U815 and reflow all the solder 
around this part and the resistors capacitors etc...
Try this and let me know.

Karl



--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:
>
> Hi Karl,
> I have gone and replaced all parts you suggested, re-seated the dac
> and went over all solders!
> No improvement, I keep getting the same problem!
> I also noticed that I get 3.79V at one of the pins of U815 instead 
of
> 4.0V(+/- .05V) as the service manual points out!
> Anyway the good news is that I found a NOS dac ($150) which I will 
try
> out as soon as it gets in(in a few days I hope).
> I'll let you know!
> Thanks,Takis.
> 
> 
> --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> >
> > Hi Takis,
> > The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for 
each 
> > voice respectivly. And Yes they are the same 2.2uF 50V Make sure 
they 
> > are 50V rating. and correct polarity (You probobly knew that)
> > But before you replace those, try this.You are saying you are 
having 
> > problems with all the voices right?
> > This points to the main DAC/Tuming circuit as you have already 
> > guessed.
> > 
> > I would look closely at:
> >  U811           The DAC        
> >  U816,U805      Multiplexer    4051
> >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> >  U814           Analog Switch  4053 
> > 
> > Any of these parts failing could cause tuning problems like you 
> > describe.
> > Now, before you replace them carfully pull them from the sockets 
and 
> > re-seat them. Sometimes corrosion on the socket/chip lead can 
cause 
> > a "not to good" connection. Also before I replaced them I would 
> > reflow the solder on the bottom of the board, as bad solder 
joints 
> > could also cause this.
> > If this does not work replace em. All except the DAC are readily 
> > available. I would wait till you replaced the other chips before 
you 
> > went searching for this DAC to see if any others are the cause. 
If 
> > one of the chips have failed, I would bet on the mux or analog 
switch.
> > It would not hurt to replace the capacitors I mentioned above, as 
> > they are probobly on their way out anyway.  
> > 
> > Let Me Know How It Goes
> > 
> > Karl
> >  
> > 
> > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > <takisdamaschis@> wrote:
> > >
> > > Hi Carl,
> > > yes I replaced all six Cx49 capacitors!
> > > What number are the other ones you're refering to?Are they also 
> > 2.2uF?
> > > Many thanks,Takis.
> > > 
> > >  
> > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > >
> > > > Hello takisdamaschis,
> > > > 
> > > > When you say output capacitors, are you talking about the 
small 
> > 2.2uF
> > > > Cx49 at the edge of the voice board? There is one for each 
voice.
> > > > There is also one of these at the output of each VCO feeding 
the 
> > VCF
> > > > If these go you can have tuning problems. Also, try resetting 
the 
> > > > software.( hold sown clear and turn power On)
> > > > 
> > > > Karl
> > > > 
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > <takisdamaschis@> wrote:
> > > > >
> > > > > Hi everyone, my xpander seems to fail the VCO tune test 
> > randomly!some
> > > > > voices fail during one test and pass on the next! there is 
no
> > > > > cosistancy on the voices that fail,it can be any one of 
them!
> > Some
> > > > > times(rarely) the vco test passes! I have the same problem 
> > sometimes
> > > > > with the Resonance and VCF but not as often!
> > > > > I have totally rebuilt the power supply,changed the battery 
and 
> > output
> > > > > bypass capacitors!All currents measure right so this is not 
a 

> > voltage
> > > > > supply problem!
> > > > > The only other part I can think of is the DAC or maybe the 
> > Timer?
> > > > > Any thoughts?
> > > > > Takis.
> > > > >
> > > >
> > >
> >
>

--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:
>
Hi Karl,
done everything you pointed out,no improvements!
Anything else you can think of before we go for the DAC?
Thanks,Takis.

> Hi Takis,
> > I also noticed that I get 3.79V at one of the pins of U815 instead 
> > of 4.0V(+/- .05V) as the service manual points out!
> 
> Okay, lets look at D805, A zener diode which provides the reference
> for the DAC.Measure this with a good voltmeter, it should be 6.9V. 
> Again, try reflowing the solder around this part and the ref circuit. 
> If you have a service 
> manual, Look at the circuit around U815 and reflow all the solder 
> around this part and the resistors capacitors etc...
> Try this and let me know.
> 
> Karl
> 
> 
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi Karl,
> > I have gone and replaced all parts you suggested, re-seated the dac
> > and went over all solders!
> > No improvement, I keep getting the same problem!
> > I also noticed that I get 3.79V at one of the pins of U815 instead 
> of
> > 4.0V(+/- .05V) as the service manual points out!
> > Anyway the good news is that I found a NOS dac ($150) which I will 
> try
> > out as soon as it gets in(in a few days I hope).
> > I'll let you know!
> > Thanks,Takis.
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > > Hi Takis,
> > > The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for 
> each 
> > > voice respectivly. And Yes they are the same 2.2uF 50V Make sure 
> they 
> > > are 50V rating. and correct polarity (You probobly knew that)
> > > But before you replace those, try this.You are saying you are 
> having 
> > > problems with all the voices right?
> > > This points to the main DAC/Tuming circuit as you have already 
> > > guessed.
> > > 
> > > I would look closely at:
> > >  U811           The DAC        
> > >  U816,U805      Multiplexer    4051
> > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > >  U814           Analog Switch  4053 
> > > 
> > > Any of these parts failing could cause tuning problems like you 
> > > describe.
> > > Now, before you replace them carfully pull them from the sockets 
> and 
> > > re-seat them. Sometimes corrosion on the socket/chip lead can 
> cause 
> > > a "not to good" connection. Also before I replaced them I would 
> > > reflow the solder on the bottom of the board, as bad solder 
> joints 
> > > could also cause this.
> > > If this does not work replace em. All except the DAC are readily 
> > > available. I would wait till you replaced the other chips before 
> you 
> > > went searching for this DAC to see if any others are the cause. 
> If 
> > > one of the chips have failed, I would bet on the mux or analog 
> switch.
> > > It would not hurt to replace the capacitors I mentioned above, as 
> > > they are probobly on their way out anyway.  
> > > 
> > > Let Me Know How It Goes
> > > 
> > > Karl
> > >  
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > Hi Carl,
> > > > yes I replaced all six Cx49 capacitors!
> > > > What number are the other ones you're refering to?Are they also 
> > > 2.2uF?
> > > > Many thanks,Takis.
> > > > 
> > > >  
> > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > >
> > > > > Hello takisdamaschis,
> > > > > 
> > > > > When you say output capacitors, are you talking about the 
> small 
> > > 2.2uF
> > > > > Cx49 at the edge of the voice board? There is one for each 
> voice.
> > > > > There is also one of these at the output of each VCO feeding 
> the 
> > > VCF
> > > > > If these go you can have tuning problems. Also, try resetting 
> the 
> > > > > software.( hold sown clear and turn power On)
> > > > > 
> > > > > Karl
> > > > > 
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > <takisdamaschis@> wrote:
> > > > > >
> > > > > > Hi everyone, my xpander seems to fail the VCO tune test 
> > > randomly!some
> > > > > > voices fail during one test and pass on the next! there is 
> no
> > > > > > cosistancy on the voices that fail,it can be any one of 
> them!
> > > Some
> > > > > > times(rarely) the vco test passes! I have the same problem 
> > > sometimes
> > > > > > with the Resonance and VCF but not as often!
> > > > > > I have totally rebuilt the power supply,changed the battery 
> and 
> > > output
> > > > > > bypass capacitors!All currents measure right so this is not 
> a 
> > > voltage
> > > > > > supply problem!
> > > > > > The only other part I can think of is the DAC or maybe the 
> > > Timer?
> > > > > > Any thoughts?
> > > > > > Takis.
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Takis,

What does the your voltmeter read when you measure the zener(D805)?
I keep thinking it's something to do with this circuit.
I am going to open mine up and see what I get.

Karl



--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:
>
> --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> >
> Hi Karl,
> done everything you pointed out,no improvements!
> Anything else you can think of before we go for the DAC?
> Thanks,Takis.
> 
> 
> > Hi Takis,
> > > I also noticed that I get 3.79V at one of the pins of U815 
instead 
> > > of 4.0V(+/- .05V) as the service manual points out!
> > 
> > Okay, lets look at D805, A zener diode which provides the 
reference
> > for the DAC.Measure this with a good voltmeter, it should be 
6.9V. 
> > Again, try reflowing the solder around this part and the ref 
circuit. 
> > If you have a service 
> > manual, Look at the circuit around U815 and reflow all the solder 
> > around this part and the resistors capacitors etc...
> > Try this and let me know.
> > 
> > Karl
> > 
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > <takisdamaschis@> wrote:
> > >
> > > Hi Karl,
> > > I have gone and replaced all parts you suggested, re-seated the 
dac
> > > and went over all solders!
> > > No improvement, I keep getting the same problem!
> > > I also noticed that I get 3.79V at one of the pins of U815 
instead 
> > of
> > > 4.0V(+/- .05V) as the service manual points out!
> > > Anyway the good news is that I found a NOS dac ($150) which I 
will 
> > try
> > > out as soon as it gets in(in a few days I hope).
> > > I'll let you know!
> > > Thanks,Takis.
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > >
> > > > Hi Takis,
> > > > The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for 
> > each 
> > > > voice respectivly. And Yes they are the same 2.2uF 50V Make 
sure 
> > they 
> > > > are 50V rating. and correct polarity (You probobly knew that)
> > > > But before you replace those, try this.You are saying you are 
> > having 
> > > > problems with all the voices right?
> > > > This points to the main DAC/Tuming circuit as you have 
already 
> > > > guessed.
> > > > 
> > > > I would look closely at:
> > > >  U811           The DAC        
> > > >  U816,U805      Multiplexer    4051
> > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > >  U814           Analog Switch  4053 
> > > > 
> > > > Any of these parts failing could cause tuning problems like 
you 
> > > > describe.
> > > > Now, before you replace them carfully pull them from the 
sockets 
> > and 
> > > > re-seat them. Sometimes corrosion on the socket/chip lead can 
> > cause 
> > > > a "not to good" connection. Also before I replaced them I 
would 
> > > > reflow the solder on the bottom of the board, as bad solder 
> > joints 
> > > > could also cause this.
> > > > If this does not work replace em. All except the DAC are 
readily 
> > > > available. I would wait till you replaced the other chips 
before 
> > you 
> > > > went searching for this DAC to see if any others are the 
cause. 
> > If 
> > > > one of the chips have failed, I would bet on the mux or 
analog 
> > switch.
> > > > It would not hurt to replace the capacitors I mentioned 
above, as 
> > > > they are probobly on their way out anyway.  
> > > > 
> > > > Let Me Know How It Goes
> > > > 
> > > > Karl
> > > >  
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > <takisdamaschis@> wrote:
> > > > >
> > > > > Hi Carl,
> > > > > yes I replaced all six Cx49 capacitors!
> > > > > What number are the other ones you're refering to?Are they 
also 
> > > > 2.2uF?
> > > > > Many thanks,Takis.
> > > > > 
> > > > >  
> > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > >
> > > > > > Hello takisdamaschis,
> > > > > > 
> > > > > > When you say output capacitors, are you talking about the 
> > small 
> > > > 2.2uF
> > > > > > Cx49 at the edge of the voice board? There is one for 
each 
> > voice.
> > > > > > There is also one of these at the output of each VCO 
feeding 
> > the 
> > > > VCF
> > > > > > If these go you can have tuning problems. Also, try 
resetting 
> > the 
> > > > > > software.( hold sown clear and turn power On)
> > > > > > 
> > > > > > Karl
> > > > > > 
> > > > > > 
> > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > <takisdamaschis@> wrote:
> > > > > > >
> > > > > > > Hi everyone, my xpander seems to fail the VCO tune test 
> > > > randomly!some
> > > > > > > voices fail during one test and pass on the next! there 
is 
> > no
> > > > > > > cosistancy on the voices that fail,it can be any one of 
> > them!
> > > > Some
> > > > > > > times(rarely) the vco test passes! I have the same 
problem 
> > > > sometimes
> > > > > > > with the Resonance and VCF but not as often!
> > > > > > > I have totally rebuilt the power supply,changed the 
battery 
> > and 
> > > > output
> > > > > > > bypass capacitors!All currents measure right so this is 
not 
> > a 
> > > > voltage
> > > > > > > supply problem!
> > > > > > > The only other part I can think of is the DAC or maybe 
the 

> > > > Timer?
> > > > > > > Any thoughts?
> > > > > > > Takis.
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Karl,
the voltmeter reads 6.38v!
Takis.

--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:

>
> Hi Takis,
> 
> What does the your voltmeter read when you measure the zener(D805)?
> I keep thinking it's something to do with this circuit.
> I am going to open mine up and see what I get.
> 
> Karl
> 
> 
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > Hi Karl,
> > done everything you pointed out,no improvements!
> > Anything else you can think of before we go for the DAC?
> > Thanks,Takis.
> > 
> > 
> > > Hi Takis,
> > > > I also noticed that I get 3.79V at one of the pins of U815 
> instead 
> > > > of 4.0V(+/- .05V) as the service manual points out!
> > > 
> > > Okay, lets look at D805, A zener diode which provides the 
> reference
> > > for the DAC.Measure this with a good voltmeter, it should be 
> 6.9V. 
> > > Again, try reflowing the solder around this part and the ref 
> circuit. 
> > > If you have a service 
> > > manual, Look at the circuit around U815 and reflow all the solder 
> > > around this part and the resistors capacitors etc...
> > > Try this and let me know.
> > > 
> > > Karl
> > > 
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > Hi Karl,
> > > > I have gone and replaced all parts you suggested, re-seated the 
> dac
> > > > and went over all solders!
> > > > No improvement, I keep getting the same problem!
> > > > I also noticed that I get 3.79V at one of the pins of U815 
> instead 
> > > of
> > > > 4.0V(+/- .05V) as the service manual points out!
> > > > Anyway the good news is that I found a NOS dac ($150) which I 
> will 
> > > try
> > > > out as soon as it gets in(in a few days I hope).
> > > > I'll let you know!
> > > > Thanks,Takis.
> > > > 
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > >
> > > > > Hi Takis,
> > > > > The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 for 
> > > each 
> > > > > voice respectivly. And Yes they are the same 2.2uF 50V Make 
> sure 
> > > they 
> > > > > are 50V rating. and correct polarity (You probobly knew that)
> > > > > But before you replace those, try this.You are saying you are 
> > > having 
> > > > > problems with all the voices right?
> > > > > This points to the main DAC/Tuming circuit as you have 
> already 
> > > > > guessed.
> > > > > 
> > > > > I would look closely at:
> > > > >  U811           The DAC        
> > > > >  U816,U805      Multiplexer    4051
> > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > >  U814           Analog Switch  4053 
> > > > > 
> > > > > Any of these parts failing could cause tuning problems like 
> you 
> > > > > describe.
> > > > > Now, before you replace them carfully pull them from the 
> sockets 
> > > and 
> > > > > re-seat them. Sometimes corrosion on the socket/chip lead can 
> > > cause 
> > > > > a "not to good" connection. Also before I replaced them I 
> would 
> > > > > reflow the solder on the bottom of the board, as bad solder 
> > > joints 
> > > > > could also cause this.
> > > > > If this does not work replace em. All except the DAC are 
> readily 
> > > > > available. I would wait till you replaced the other chips 
> before 
> > > you 
> > > > > went searching for this DAC to see if any others are the 
> cause. 
> > > If 
> > > > > one of the chips have failed, I would bet on the mux or 
> analog 
> > > switch.
> > > > > It would not hurt to replace the capacitors I mentioned 
> above, as 
> > > > > they are probobly on their way out anyway.  
> > > > > 
> > > > > Let Me Know How It Goes
> > > > > 
> > > > > Karl
> > > > >  
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > <takisdamaschis@> wrote:
> > > > > >
> > > > > > Hi Carl,
> > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > What number are the other ones you're refering to?Are they 
> also 
> > > > > 2.2uF?
> > > > > > Many thanks,Takis.
> > > > > > 
> > > > > >  
> > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > > >
> > > > > > > Hello takisdamaschis,
> > > > > > > 
> > > > > > > When you say output capacitors, are you talking about the 
> > > small 
> > > > > 2.2uF
> > > > > > > Cx49 at the edge of the voice board? There is one for 
> each 
> > > voice.
> > > > > > > There is also one of these at the output of each VCO 
> feeding 
> > > the 
> > > > > VCF
> > > > > > > If these go you can have tuning problems. Also, try 
> resetting 
> > > the 
> > > > > > > software.( hold sown clear and turn power On)
> > > > > > > 
> > > > > > > Karl
> > > > > > > 
> > > > > > > 
> > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > <takisdamaschis@> wrote:
> > > > > > > >
> > > > > > > > Hi everyone, my xpander seems to fail the VCO tune test 
> > > > > randomly!some
> > > > > > > > voices fail during one test and pass on the next! there 
> is 
> > > no
> > > > > > > > cosistancy on the voices that fail,it can be any one of 
> > > them!
> > > > > Some
> > > > > > > > times(rarely) the vco test passes! I have the same 
> problem 
> > > > > sometimes
> > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > I have totally rebuilt the power supply,changed the 
> battery 
> > > and 
> > > > > output
> > > > > > > > bypass capacitors!All currents measure right so this is 
> not 
> > > a 
> > > > > voltage
> > > > > > > > supply problem!
> > > > > > > > The only other part I can think of is the DAC or maybe 
> the 
> > > > > Timer?
> > > > > > > > Any thoughts?
> > > > > > > > Takis.
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hello Takis Where did you make the measurement? This sounds somewhat like the reading I got- when I measured one of the diodes near the battery. (as directed

Tip... A zener diode is always noisy . It generates ripples in the voltage. Ripples in referance voltage may cause autotune to fail. To avoid these ripples

Hi,
are you talking about the D805 diode?
If so, mine does not have a capacitor parallel to it!
Did yours have one all along? If so please let me know of it's specs
so that I can add one myself!
Thanks!

 
--- In xpantastic@yahoogroups.com, "bjorn roland" <bjorn.roland@...>
wrote:
>
> Tip...
> A zener diode is always "noisy". It generates ripples in the voltage.
> Ripples in referance voltage may cause autotune to fail.
> To avoid these ripples there is always a capacitor mounted in
paralell to
> the zener
> to flatten out these ripples. Check ac voltage also, not only dc.
> Ac will show ripples. Should be zero, but if not check out this
capacitor.
> 
> On Thu, Oct 2, 2008 at 5:02 PM, Tony Cappellini <cappy2112@...> wrote:
> 
> >    Hello Takis
> >
> > Where did you make the measurement?
> > This sounds somewhat like the reading I got- when I measured one
of the
> > diodes near the battery. (as directed in the service manual test
procedure)
> >
> >
> >
> > On Thu, Oct 2, 2008 at 1:12 AM, takisdamaschis
<takisdamaschis@...>wrote:
> >
> >>   Hi Karl,
> >> the voltmeter reads 6.38v!
> >>
> >> Takis.
> >>
> >> --- In xpantastic@yahoogroups.com <xpantastic%40yahoogroups.com>,
"Karl"
> >> <shire03@> wrote:
> >> >
> >> > Hi Takis,
> >> >
> >> > What does the your voltmeter read when you measure the zener(D805)?
> >> > I keep thinking it's something to do with this circuit.
> >> > I am going to open mine up and see what I get.
> >> >
> >> > Karl
> >> >
> >> >
> >> >
> >> > --- In xpantastic@yahoogroups.com <xpantastic%40yahoogroups.com>,
> >> "takisdamaschis"
> >> > <takisdamaschis@> wrote:
> >> > >
> >> > > --- In xpantastic@yahoogroups.com <xpantastic%40yahoogroups.com>,
> >> "Karl" <shire03@> wrote:
> >> > > >
> >> > > Hi Karl,
> >> > > done everything you pointed out,no improvements!
> >> > > Anything else you can think of before we go for the DAC?
> >> > > Thanks,Takis.
> >> > >
> >> > >
> >> > > > Hi Takis,
> >> > > > > I also noticed that I get 3.79V at one of the pins of U815
> >> > instead
> >> > > > > of 4.0V(+/- .05V) as the service manual points out!
> >> > > >
> >> > > > Okay, lets look at D805, A zener diode which provides the
> >> > reference
> >> > > > for the DAC.Measure this with a good voltmeter, it should be
> >> > 6.9V.
> >> > > > Again, try reflowing the solder around this part and the ref
> >> > circuit.
> >> > > > If you have a service
> >> > > > manual, Look at the circuit around U815 and reflow all the
solder
> >> > > > around this part and the resistors capacitors etc...
> >> > > > Try this and let me know.
> >> > > >
> >> > > > Karl
> >> > > >
> >> > > >
> >> > > >
> >> > > > --- In xpantastic@yahoogroups.com
<xpantastic%40yahoogroups.com>,
> >> "takisdamaschis"
> >> > > > <takisdamaschis@> wrote:
> >> > > > >
> >> > > > > Hi Karl,
> >> > > > > I have gone and replaced all parts you suggested,
re-seated the
> >> > dac
> >> > > > > and went over all solders!
> >> > > > > No improvement, I keep getting the same problem!
> >> > > > > I also noticed that I get 3.79V at one of the pins of U815
> >> > instead
> >> > > > of
> >> > > > > 4.0V(+/- .05V) as the service manual points out!
> >> > > > > Anyway the good news is that I found a NOS dac ($150) which I
> >> > will
> >> > > > try
> >> > > > > out as soon as it gets in(in a few days I hope).
> >> > > > > I'll let you know!
> >> > > > > Thanks,Takis.
> >> > > > >
> >> > > > >
> >> > > > > --- In xpantastic@yahoogroups.com
<xpantastic%40yahoogroups.com>,
> >> "Karl" <shire03@> wrote:
> >> > > > > >
> >> > > > > > Hi Takis,
> >> > > > > > The other caps are Cx33 and Cx37 with x being
2,3,4,5,6,7 for
> >> > > > each
> >> > > > > > voice respectivly. And Yes they are the same 2.2uF 50V Make
> >> > sure
> >> > > > they
> >> > > > > > are 50V rating. and correct polarity (You probobly knew
that)
> >> > > > > > But before you replace those, try this.You are saying
you are
> >> > > > having
> >> > > > > > problems with all the voices right?
> >> > > > > > This points to the main DAC/Tuming circuit as you have
> >> > already
> >> > > > > > guessed.
> >> > > > > >
> >> > > > > > I would look closely at:
> >> > > > > > U811 The DAC
> >> > > > > > U816,U805 Multiplexer 4051
> >> > > > > > U812,U815,U813 Op Amps TLO81,TLO84,TLO81
> >> > > > > > U814 Analog Switch 4053
> >> > > > > >
> >> > > > > > Any of these parts failing could cause tuning problems like
> >> > you
> >> > > > > > describe.
> >> > > > > > Now, before you replace them carfully pull them from the
> >> > sockets
> >> > > > and
> >> > > > > > re-seat them. Sometimes corrosion on the socket/chip
lead can
> >> > > > cause
> >> > > > > > a "not to good" connection. Also before I replaced them I
> >> > would
> >> > > > > > reflow the solder on the bottom of the board, as bad solder
> >> > > > joints
> >> > > > > > could also cause this.
> >> > > > > > If this does not work replace em. All except the DAC are
> >> > readily
> >> > > > > > available. I would wait till you replaced the other chips
> >> > before
> >> > > > you
> >> > > > > > went searching for this DAC to see if any others are the
> >> > cause.
> >> > > > If
> >> > > > > > one of the chips have failed, I would bet on the mux or
> >> > analog
> >> > > > switch.
> >> > > > > > It would not hurt to replace the capacitors I mentioned
> >> > above, as
> >> > > > > > they are probobly on their way out anyway.
> >> > > > > >
> >> > > > > > Let Me Know How It Goes
> >> > > > > >
> >> > > > > > Karl
> >> > > > > >
> >> > > > > >
> >> > > > > > --- In
xpantastic@yahoogroups.com<xpantastic%40yahoogroups.com>,
> >> "takisdamaschis"
> >> > > > > > <takisdamaschis@> wrote:
> >> > > > > > >
> >> > > > > > > Hi Carl,
> >> > > > > > > yes I replaced all six Cx49 capacitors!
> >> > > > > > > What number are the other ones you're refering to?Are
they
> >> > also
> >> > > > > > 2.2uF?
> >> > > > > > > Many thanks,Takis.
> >> > > > > > >
> >> > > > > > >
> >> > > > > > > --- In
xpantastic@yahoogroups.com<xpantastic%40yahoogroups.com>,
> >> "Karl" <shire03@> wrote:
> >> > > > > > > >
> >> > > > > > > > Hello takisdamaschis,
> >> > > > > > > >
> >> > > > > > > > When you say output capacitors, are you talking
about the
> >> > > > small
> >> > > > > > 2.2uF
> >> > > > > > > > Cx49 at the edge of the voice board? There is one for
> >> > each
> >> > > > voice.
> >> > > > > > > > There is also one of these at the output of each VCO
> >> > feeding
> >> > > > the
> >> > > > > > VCF
> >> > > > > > > > If these go you can have tuning problems. Also, try
> >> > resetting
> >> > > > the
> >> > > > > > > > software.( hold sown clear and turn power On)
> >> > > > > > > >
> >> > > > > > > > Karl
> >> > > > > > > >
> >> > > > > > > >
> >> > > > > > > > --- In
xpantastic@...m<xpantastic%40yahoogroups.com>,
> >> "takisdamaschis"
> >> > > > > > > > <takisdamaschis@> wrote:
> >> > > > > > > > >
> >> > > > > > > > > Hi everyone, my xpander seems to fail the VCO
tune test
> >> > > > > > randomly!some
> >> > > > > > > > > voices fail during one test and pass on the next!
there
> >> > is
> >> > > > no
> >> > > > > > > > > cosistancy on the voices that fail,it can be any
one of
> >> > > > them!
> >> > > > > > Some
> >> > > > > > > > > times(rarely) the vco test passes! I have the same
> >> > problem
> >> > > > > > sometimes
> >> > > > > > > > > with the Resonance and VCF but not as often!
> >> > > > > > > > > I have totally rebuilt the power supply,changed the
> >> > battery
> >> > > > and
> >> > > > > > output
> >> > > > > > > > > bypass capacitors!All currents measure right so
this is
> >> > not
> >> > > > a
> >> > > > > > voltage
> >> > > > > > > > > supply problem!
> >> > > > > > > > > The only other part I can think of is the DAC or
maybe

> >> > the
> >> > > > > > Timer?
> >> > > > > > > > > Any thoughts?
> >> > > > > > > > > Takis.
> >> > > > > > > > >
> >> > > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> >>
> > 
> >
>

Hi Takis,
I measured the D805 in mine: 6.95 Vdc. I notice it's a diode in a 
transistor package. This is a very accurate reference diode. It 
should read at least 6.9 Volts. Pin 1 is not used. I measured from 
The left side of R856 ( just below it) to the middle leg of the 
diode.  My schematics identify this as a 6.9 V Zener. If the one in 
yours shows a lower voltage than that, maybe this is causing the 
tuning errors.  The diode may not be bad, something maybe dragging it 
down. I would take U815 out (turn Off first), then measure it again. 
If you can't get 6.9V out of that ref, I would replace it.  
BTW about where is the adjustment trimmer pointing?

Karl




--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:
>
> Hi Karl,
> the voltmeter reads 6.38v!
> Takis.
> 
> --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> >
> > Hi Takis,
> > 
> > What does the your voltmeter read when you measure the zener
(D805)?
> > I keep thinking it's something to do with this circuit.
> > I am going to open mine up and see what I get.
> > 
> > Karl
> > 
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > <takisdamaschis@> wrote:
> > >
> > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > >
> > > Hi Karl,
> > > done everything you pointed out,no improvements!
> > > Anything else you can think of before we go for the DAC?
> > > Thanks,Takis.
> > > 
> > > 
> > > > Hi Takis,
> > > > > I also noticed that I get 3.79V at one of the pins of U815 
> > instead 
> > > > > of 4.0V(+/- .05V) as the service manual points out!
> > > > 
> > > > Okay, lets look at D805, A zener diode which provides the 
> > reference
> > > > for the DAC.Measure this with a good voltmeter, it should be 
> > 6.9V. 
> > > > Again, try reflowing the solder around this part and the ref 
> > circuit. 
> > > > If you have a service 
> > > > manual, Look at the circuit around U815 and reflow all the 
solder 
> > > > around this part and the resistors capacitors etc...
> > > > Try this and let me know.
> > > > 
> > > > Karl
> > > > 
> > > > 
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > <takisdamaschis@> wrote:
> > > > >
> > > > > Hi Karl,
> > > > > I have gone and replaced all parts you suggested, re-seated 
the 
> > dac
> > > > > and went over all solders!
> > > > > No improvement, I keep getting the same problem!
> > > > > I also noticed that I get 3.79V at one of the pins of U815 
> > instead 
> > > > of
> > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > Anyway the good news is that I found a NOS dac ($150) which 
I 
> > will 
> > > > try
> > > > > out as soon as it gets in(in a few days I hope).
> > > > > I'll let you know!
> > > > > Thanks,Takis.
> > > > > 
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > >
> > > > > > Hi Takis,
> > > > > > The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 
for 
> > > > each 
> > > > > > voice respectivly. And Yes they are the same 2.2uF 50V 
Make 
> > sure 
> > > > they 
> > > > > > are 50V rating. and correct polarity (You probobly knew 
that)
> > > > > > But before you replace those, try this.You are saying you 
are 
> > > > having 
> > > > > > problems with all the voices right?
> > > > > > This points to the main DAC/Tuming circuit as you have 
> > already 
> > > > > > guessed.
> > > > > > 
> > > > > > I would look closely at:
> > > > > >  U811           The DAC        
> > > > > >  U816,U805      Multiplexer    4051
> > > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > > >  U814           Analog Switch  4053 
> > > > > > 
> > > > > > Any of these parts failing could cause tuning problems 
like 
> > you 
> > > > > > describe.
> > > > > > Now, before you replace them carfully pull them from the 
> > sockets 
> > > > and 
> > > > > > re-seat them. Sometimes corrosion on the socket/chip lead 
can 
> > > > cause 
> > > > > > a "not to good" connection. Also before I replaced them I 
> > would 
> > > > > > reflow the solder on the bottom of the board, as bad 
solder 
> > > > joints 
> > > > > > could also cause this.
> > > > > > If this does not work replace em. All except the DAC are 
> > readily 
> > > > > > available. I would wait till you replaced the other chips 
> > before 
> > > > you 
> > > > > > went searching for this DAC to see if any others are the 
> > cause. 
> > > > If 
> > > > > > one of the chips have failed, I would bet on the mux or 
> > analog 
> > > > switch.
> > > > > > It would not hurt to replace the capacitors I mentioned 
> > above, as 
> > > > > > they are probobly on their way out anyway.  
> > > > > > 
> > > > > > Let Me Know How It Goes
> > > > > > 
> > > > > > Karl
> > > > > >  
> > > > > > 
> > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > <takisdamaschis@> wrote:
> > > > > > >
> > > > > > > Hi Carl,
> > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > What number are the other ones you're refering to?Are 
they 
> > also 
> > > > > > 2.2uF?
> > > > > > > Many thanks,Takis.
> > > > > > > 
> > > > > > >  
> > > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
wrote:
> > > > > > > >
> > > > > > > > Hello takisdamaschis,
> > > > > > > > 
> > > > > > > > When you say output capacitors, are you talking about 
the 
> > > > small 
> > > > > > 2.2uF
> > > > > > > > Cx49 at the edge of the voice board? There is one for 
> > each 
> > > > voice.
> > > > > > > > There is also one of these at the output of each VCO 
> > feeding 
> > > > the 
> > > > > > VCF
> > > > > > > > If these go you can have tuning problems. Also, try 
> > resetting 
> > > > the 
> > > > > > > > software.( hold sown clear and turn power On)
> > > > > > > > 
> > > > > > > > Karl
> > > > > > > > 
> > > > > > > > 
> > > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > >
> > > > > > > > > Hi everyone, my xpander seems to fail the VCO tune 
test 
> > > > > > randomly!some
> > > > > > > > > voices fail during one test and pass on the next! 
there 
> > is 
> > > > no
> > > > > > > > > cosistancy on the voices that fail,it can be any 
one of 
> > > > them!
> > > > > > Some
> > > > > > > > > times(rarely) the vco test passes! I have the same 
> > problem 
> > > > > > sometimes
> > > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > > I have totally rebuilt the power supply,changed the 
> > battery 
> > > > and 
> > > > > > output
> > > > > > > > > bypass capacitors!All currents measure right so 
this is 
> > not 
> > > > a 
> > > > > > voltage
> > > > > > > > > supply problem!
> > > > > > > > > The only other part I can think of is the DAC or 
maybe 

> > the 
> > > > > > Timer?
> > > > > > > > > Any thoughts?
> > > > > > > > > Takis.
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Tony, 
I'm talking about D805 at the DAC circuit!



--- In xpantastic@yahoogroups.com, "Tony Cappellini" <cappy2112@...>
wrote:
>
> Hello Takis
> 
> Where did you make the measurement?
> This sounds somewhat like the reading I got- when I measured one of the
> diodes near the battery. (as directed in the service manual test
procedure)
> 
> 
> On Thu, Oct 2, 2008 at 1:12 AM, takisdamaschis
<takisdamaschis@...>wrote:
> 
> >   Hi Karl,
> > the voltmeter reads 6.38v!
> >
> > Takis.
> >
> > --- In xpantastic@yahoogroups.com <xpantastic%40yahoogroups.com>,
"Karl"
> > <shire03@> wrote:
> > >
> > > Hi Takis,
> > >
> > > What does the your voltmeter read when you measure the zener(D805)?
> > > I keep thinking it's something to do with this circuit.
> > > I am going to open mine up and see what I get.
> > >
> > > Karl
> > >
> > >
> > >
> > > --- In xpantastic@yahoogroups.com <xpantastic%40yahoogroups.com>,
> > "takisdamaschis"
> > > <takisdamaschis@> wrote:
> > > >
> > > > --- In xpantastic@yahoogroups.com <xpantastic%40yahoogroups.com>,
> > "Karl" <shire03@> wrote:
> > > > >
> > > > Hi Karl,
> > > > done everything you pointed out,no improvements!
> > > > Anything else you can think of before we go for the DAC?
> > > > Thanks,Takis.
> > > >
> > > >
> > > > > Hi Takis,
> > > > > > I also noticed that I get 3.79V at one of the pins of U815
> > > instead
> > > > > > of 4.0V(+/- .05V) as the service manual points out!
> > > > >
> > > > > Okay, lets look at D805, A zener diode which provides the
> > > reference
> > > > > for the DAC.Measure this with a good voltmeter, it should be
> > > 6.9V.
> > > > > Again, try reflowing the solder around this part and the ref
> > > circuit.
> > > > > If you have a service
> > > > > manual, Look at the circuit around U815 and reflow all the
solder
> > > > > around this part and the resistors capacitors etc...
> > > > > Try this and let me know.
> > > > >
> > > > > Karl
> > > > >
> > > > >
> > > > >
> > > > > --- In xpantastic@yahoogroups.com
<xpantastic%40yahoogroups.com>,
> > "takisdamaschis"
> > > > > <takisdamaschis@> wrote:
> > > > > >
> > > > > > Hi Karl,
> > > > > > I have gone and replaced all parts you suggested,
re-seated the
> > > dac
> > > > > > and went over all solders!
> > > > > > No improvement, I keep getting the same problem!
> > > > > > I also noticed that I get 3.79V at one of the pins of U815
> > > instead
> > > > > of
> > > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > > Anyway the good news is that I found a NOS dac ($150) which I
> > > will
> > > > > try
> > > > > > out as soon as it gets in(in a few days I hope).
> > > > > > I'll let you know!
> > > > > > Thanks,Takis.
> > > > > >
> > > > > >
> > > > > > --- In xpantastic@yahoogroups.com
<xpantastic%40yahoogroups.com>,
> > "Karl" <shire03@> wrote:
> > > > > > >
> > > > > > > Hi Takis,
> > > > > > > The other caps are Cx33 and Cx37 with x being
2,3,4,5,6,7 for
> > > > > each
> > > > > > > voice respectivly. And Yes they are the same 2.2uF 50V Make
> > > sure
> > > > > they
> > > > > > > are 50V rating. and correct polarity (You probobly knew
that)
> > > > > > > But before you replace those, try this.You are saying
you are
> > > > > having
> > > > > > > problems with all the voices right?
> > > > > > > This points to the main DAC/Tuming circuit as you have
> > > already
> > > > > > > guessed.
> > > > > > >
> > > > > > > I would look closely at:
> > > > > > > U811 The DAC
> > > > > > > U816,U805 Multiplexer 4051
> > > > > > > U812,U815,U813 Op Amps TLO81,TLO84,TLO81
> > > > > > > U814 Analog Switch 4053
> > > > > > >
> > > > > > > Any of these parts failing could cause tuning problems like
> > > you
> > > > > > > describe.
> > > > > > > Now, before you replace them carfully pull them from the
> > > sockets
> > > > > and
> > > > > > > re-seat them. Sometimes corrosion on the socket/chip
lead can
> > > > > cause
> > > > > > > a "not to good" connection. Also before I replaced them I
> > > would
> > > > > > > reflow the solder on the bottom of the board, as bad solder
> > > > > joints
> > > > > > > could also cause this.
> > > > > > > If this does not work replace em. All except the DAC are
> > > readily
> > > > > > > available. I would wait till you replaced the other chips
> > > before
> > > > > you
> > > > > > > went searching for this DAC to see if any others are the
> > > cause.
> > > > > If
> > > > > > > one of the chips have failed, I would bet on the mux or
> > > analog
> > > > > switch.
> > > > > > > It would not hurt to replace the capacitors I mentioned
> > > above, as
> > > > > > > they are probobly on their way out anyway.
> > > > > > >
> > > > > > > Let Me Know How It Goes
> > > > > > >
> > > > > > > Karl
> > > > > > >
> > > > > > >
> > > > > > > --- In xpantastic@yahoogroups.com
<xpantastic%40yahoogroups.com>,
> > "takisdamaschis"
> > > > > > > <takisdamaschis@> wrote:
> > > > > > > >
> > > > > > > > Hi Carl,
> > > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > > What number are the other ones you're refering to?Are they
> > > also
> > > > > > > 2.2uF?
> > > > > > > > Many thanks,Takis.
> > > > > > > >
> > > > > > > >
> > > > > > > > --- In
xpantastic@yahoogroups.com<xpantastic%40yahoogroups.com>,
> > "Karl" <shire03@> wrote:
> > > > > > > > >
> > > > > > > > > Hello takisdamaschis,
> > > > > > > > >
> > > > > > > > > When you say output capacitors, are you talking
about the
> > > > > small
> > > > > > > 2.2uF
> > > > > > > > > Cx49 at the edge of the voice board? There is one for
> > > each
> > > > > voice.
> > > > > > > > > There is also one of these at the output of each VCO
> > > feeding
> > > > > the
> > > > > > > VCF
> > > > > > > > > If these go you can have tuning problems. Also, try
> > > resetting
> > > > > the
> > > > > > > > > software.( hold sown clear and turn power On)
> > > > > > > > >
> > > > > > > > > Karl
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > --- In
xpantastic@yahoogroups.com<xpantastic%40yahoogroups.com>,
> > "takisdamaschis"
> > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > >
> > > > > > > > > > Hi everyone, my xpander seems to fail the VCO tune
test
> > > > > > > randomly!some
> > > > > > > > > > voices fail during one test and pass on the next!
there
> > > is
> > > > > no
> > > > > > > > > > cosistancy on the voices that fail,it can be any
one of
> > > > > them!
> > > > > > > Some
> > > > > > > > > > times(rarely) the vco test passes! I have the same
> > > problem
> > > > > > > sometimes
> > > > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > > > I have totally rebuilt the power supply,changed the
> > > battery
> > > > > and
> > > > > > > output
> > > > > > > > > > bypass capacitors!All currents measure right so
this is

> > > not
> > > > > a
> > > > > > > voltage
> > > > > > > > > > supply problem!
> > > > > > > > > > The only other part I can think of is the DAC or maybe
> > > the
> > > > > > > Timer?
> > > > > > > > > > Any thoughts?
> > > > > > > > > > Takis.
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> >  
> >
>

Hi Karl,
I just got the new DAC! It's an HS3140C.I installed it
and.....nothing!Every test fails now instead of only some VCO's!
My original DAC is an MP7614KN, are these two incompatible and if so
why are they mentioned as both able to do the job?
Furtermore is there anything else I should have done when I replaced
the DAC that is not mentioned in the manual?
Thanks,Takis.


--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:

>
> Hi Takis,
> I measured the D805 in mine: 6.95 Vdc. I notice it's a diode in a 
> transistor package. This is a very accurate reference diode. It 
> should read at least 6.9 Volts. Pin 1 is not used. I measured from 
> The left side of R856 ( just below it) to the middle leg of the 
> diode.  My schematics identify this as a 6.9 V Zener. If the one in 
> yours shows a lower voltage than that, maybe this is causing the 
> tuning errors.  The diode may not be bad, something maybe dragging it 
> down. I would take U815 out (turn Off first), then measure it again. 
> If you can't get 6.9V out of that ref, I would replace it.  
> BTW about where is the adjustment trimmer pointing?
> 
> Karl
> 
> 
> 
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi Karl,
> > the voltmeter reads 6.38v!
> > Takis.
> > 
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > > Hi Takis,
> > > 
> > > What does the your voltmeter read when you measure the zener
> (D805)?
> > > I keep thinking it's something to do with this circuit.
> > > I am going to open mine up and see what I get.
> > > 
> > > Karl
> > > 
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > >
> > > > Hi Karl,
> > > > done everything you pointed out,no improvements!
> > > > Anything else you can think of before we go for the DAC?
> > > > Thanks,Takis.
> > > > 
> > > > 
> > > > > Hi Takis,
> > > > > > I also noticed that I get 3.79V at one of the pins of U815 
> > > instead 
> > > > > > of 4.0V(+/- .05V) as the service manual points out!
> > > > > 
> > > > > Okay, lets look at D805, A zener diode which provides the 
> > > reference
> > > > > for the DAC.Measure this with a good voltmeter, it should be 
> > > 6.9V. 
> > > > > Again, try reflowing the solder around this part and the ref 
> > > circuit. 
> > > > > If you have a service 
> > > > > manual, Look at the circuit around U815 and reflow all the 
> solder 
> > > > > around this part and the resistors capacitors etc...
> > > > > Try this and let me know.
> > > > > 
> > > > > Karl
> > > > > 
> > > > > 
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > <takisdamaschis@> wrote:
> > > > > >
> > > > > > Hi Karl,
> > > > > > I have gone and replaced all parts you suggested, re-seated 
> the 
> > > dac
> > > > > > and went over all solders!
> > > > > > No improvement, I keep getting the same problem!
> > > > > > I also noticed that I get 3.79V at one of the pins of U815 
> > > instead 
> > > > > of
> > > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > > Anyway the good news is that I found a NOS dac ($150) which 
> I 
> > > will 
> > > > > try
> > > > > > out as soon as it gets in(in a few days I hope).
> > > > > > I'll let you know!
> > > > > > Thanks,Takis.
> > > > > > 
> > > > > > 
> > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > > >
> > > > > > > Hi Takis,
> > > > > > > The other caps are Cx33 and Cx37 with x being 2,3,4,5,6,7 
> for 
> > > > > each 
> > > > > > > voice respectivly. And Yes they are the same 2.2uF 50V 
> Make 
> > > sure 
> > > > > they 
> > > > > > > are 50V rating. and correct polarity (You probobly knew 
> that)
> > > > > > > But before you replace those, try this.You are saying you 
> are 
> > > > > having 
> > > > > > > problems with all the voices right?
> > > > > > > This points to the main DAC/Tuming circuit as you have 
> > > already 
> > > > > > > guessed.
> > > > > > > 
> > > > > > > I would look closely at:
> > > > > > >  U811           The DAC        
> > > > > > >  U816,U805      Multiplexer    4051
> > > > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > > > >  U814           Analog Switch  4053 
> > > > > > > 
> > > > > > > Any of these parts failing could cause tuning problems 
> like 
> > > you 
> > > > > > > describe.
> > > > > > > Now, before you replace them carfully pull them from the 
> > > sockets 
> > > > > and 
> > > > > > > re-seat them. Sometimes corrosion on the socket/chip lead 
> can 
> > > > > cause 
> > > > > > > a "not to good" connection. Also before I replaced them I 
> > > would 
> > > > > > > reflow the solder on the bottom of the board, as bad 
> solder 
> > > > > joints 
> > > > > > > could also cause this.
> > > > > > > If this does not work replace em. All except the DAC are 
> > > readily 
> > > > > > > available. I would wait till you replaced the other chips 
> > > before 
> > > > > you 
> > > > > > > went searching for this DAC to see if any others are the 
> > > cause. 
> > > > > If 
> > > > > > > one of the chips have failed, I would bet on the mux or 
> > > analog 
> > > > > switch.
> > > > > > > It would not hurt to replace the capacitors I mentioned 
> > > above, as 
> > > > > > > they are probobly on their way out anyway.  
> > > > > > > 
> > > > > > > Let Me Know How It Goes
> > > > > > > 
> > > > > > > Karl
> > > > > > >  
> > > > > > > 
> > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > <takisdamaschis@> wrote:
> > > > > > > >
> > > > > > > > Hi Carl,
> > > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > > What number are the other ones you're refering to?Are 
> they 
> > > also 
> > > > > > > 2.2uF?
> > > > > > > > Many thanks,Takis.
> > > > > > > > 
> > > > > > > >  
> > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
> wrote:
> > > > > > > > >
> > > > > > > > > Hello takisdamaschis,
> > > > > > > > > 
> > > > > > > > > When you say output capacitors, are you talking about 
> the 
> > > > > small 
> > > > > > > 2.2uF
> > > > > > > > > Cx49 at the edge of the voice board? There is one for 
> > > each 
> > > > > voice.
> > > > > > > > > There is also one of these at the output of each VCO 
> > > feeding 
> > > > > the 
> > > > > > > VCF
> > > > > > > > > If these go you can have tuning problems. Also, try 
> > > resetting 
> > > > > the 
> > > > > > > > > software.( hold sown clear and turn power On)
> > > > > > > > > 
> > > > > > > > > Karl
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > >
> > > > > > > > > > Hi everyone, my xpander seems to fail the VCO tune 
> test 
> > > > > > > randomly!some
> > > > > > > > > > voices fail during one test and pass on the next! 
> there 
> > > is 
> > > > > no
> > > > > > > > > > cosistancy on the voices that fail,it can be any 
> one of 
> > > > > them!
> > > > > > > Some
> > > > > > > > > > times(rarely) the vco test passes! I have the same 
> > > problem 
> > > > > > > sometimes
> > > > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > > > I have totally rebuilt the power supply,changed the 
> > > battery 
> > > > > and 
> > > > > > > output
> > > > > > > > > > bypass capacitors!All currents measure right so 
> this is 
> > > not 
> > > > > a 
> > > > > > > voltage
> > > > > > > > > > supply problem!
> > > > > > > > > > The only other part I can think of is the DAC or 
> maybe 
> > > the 
> > > > > > > Timer?
> > > > > > > > > > Any thoughts?
> > > > > > > > > > Takis.
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Takis, 
On page 34 of the Xpander service manual there is a DAC calibrtion 
procedure. A different chip would need a calibration.
What about the reference voltage? 

Karl





--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:
>
> Hi Karl,
> I just got the new DAC! It's an HS3140C.I installed it
> and.....nothing!Every test fails now instead of only some VCO's!
> My original DAC is an MP7614KN, are these two incompatible and if so
> why are they mentioned as both able to do the job?
> Furtermore is there anything else I should have done when I replaced
> the DAC that is not mentioned in the manual?
> Thanks,Takis.
> 
> 
> --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> >
> > Hi Takis,
> > I measured the D805 in mine: 6.95 Vdc. I notice it's a diode in a 
> > transistor package. This is a very accurate reference diode. It 
> > should read at least 6.9 Volts. Pin 1 is not used. I measured 
from 
> > The left side of R856 ( just below it) to the middle leg of the 
> > diode.  My schematics identify this as a 6.9 V Zener. If the one 
in 
> > yours shows a lower voltage than that, maybe this is causing the 
> > tuning errors.  The diode may not be bad, something maybe 
dragging it 
> > down. I would take U815 out (turn Off first), then measure it 
again. 
> > If you can't get 6.9V out of that ref, I would replace it.  
> > BTW about where is the adjustment trimmer pointing?
> > 
> > Karl
> > 
> > 
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > <takisdamaschis@> wrote:
> > >
> > > Hi Karl,
> > > the voltmeter reads 6.38v!
> > > Takis.
> > > 
> > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > >
> > > > Hi Takis,
> > > > 
> > > > What does the your voltmeter read when you measure the zener
> > (D805)?
> > > > I keep thinking it's something to do with this circuit.
> > > > I am going to open mine up and see what I get.
> > > > 
> > > > Karl
> > > > 
> > > > 
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > <takisdamaschis@> wrote:
> > > > >
> > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > >
> > > > > Hi Karl,
> > > > > done everything you pointed out,no improvements!
> > > > > Anything else you can think of before we go for the DAC?
> > > > > Thanks,Takis.
> > > > > 
> > > > > 
> > > > > > Hi Takis,
> > > > > > > I also noticed that I get 3.79V at one of the pins of 
U815 
> > > > instead 
> > > > > > > of 4.0V(+/- .05V) as the service manual points out!
> > > > > > 
> > > > > > Okay, lets look at D805, A zener diode which provides the 
> > > > reference
> > > > > > for the DAC.Measure this with a good voltmeter, it should 
be 
> > > > 6.9V. 
> > > > > > Again, try reflowing the solder around this part and the 
ref 
> > > > circuit. 
> > > > > > If you have a service 
> > > > > > manual, Look at the circuit around U815 and reflow all 
the 
> > solder 
> > > > > > around this part and the resistors capacitors etc...
> > > > > > Try this and let me know.
> > > > > > 
> > > > > > Karl
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > <takisdamaschis@> wrote:
> > > > > > >
> > > > > > > Hi Karl,
> > > > > > > I have gone and replaced all parts you suggested, re-
seated 
> > the 
> > > > dac
> > > > > > > and went over all solders!
> > > > > > > No improvement, I keep getting the same problem!
> > > > > > > I also noticed that I get 3.79V at one of the pins of 
U815 
> > > > instead 
> > > > > > of
> > > > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > > > Anyway the good news is that I found a NOS dac ($150) 
which 
> > I 
> > > > will 
> > > > > > try
> > > > > > > out as soon as it gets in(in a few days I hope).
> > > > > > > I'll let you know!
> > > > > > > Thanks,Takis.
> > > > > > > 
> > > > > > > 
> > > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
wrote:
> > > > > > > >
> > > > > > > > Hi Takis,
> > > > > > > > The other caps are Cx33 and Cx37 with x being 
2,3,4,5,6,7 
> > for 
> > > > > > each 
> > > > > > > > voice respectivly. And Yes they are the same 2.2uF 
50V 
> > Make 
> > > > sure 
> > > > > > they 
> > > > > > > > are 50V rating. and correct polarity (You probobly 
knew 
> > that)
> > > > > > > > But before you replace those, try this.You are saying 
you 
> > are 
> > > > > > having 
> > > > > > > > problems with all the voices right?
> > > > > > > > This points to the main DAC/Tuming circuit as you 
have 
> > > > already 
> > > > > > > > guessed.
> > > > > > > > 
> > > > > > > > I would look closely at:
> > > > > > > >  U811           The DAC        
> > > > > > > >  U816,U805      Multiplexer    4051
> > > > > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > > > > >  U814           Analog Switch  4053 
> > > > > > > > 
> > > > > > > > Any of these parts failing could cause tuning 
problems 
> > like 
> > > > you 
> > > > > > > > describe.
> > > > > > > > Now, before you replace them carfully pull them from 
the 
> > > > sockets 
> > > > > > and 
> > > > > > > > re-seat them. Sometimes corrosion on the socket/chip 
lead 
> > can 
> > > > > > cause 
> > > > > > > > a "not to good" connection. Also before I replaced 
them I 
> > > > would 
> > > > > > > > reflow the solder on the bottom of the board, as bad 
> > solder 
> > > > > > joints 
> > > > > > > > could also cause this.
> > > > > > > > If this does not work replace em. All except the DAC 
are 
> > > > readily 
> > > > > > > > available. I would wait till you replaced the other 
chips 
> > > > before 
> > > > > > you 
> > > > > > > > went searching for this DAC to see if any others are 
the 
> > > > cause. 
> > > > > > If 
> > > > > > > > one of the chips have failed, I would bet on the mux 
or 
> > > > analog 
> > > > > > switch.
> > > > > > > > It would not hurt to replace the capacitors I 
mentioned 
> > > > above, as 
> > > > > > > > they are probobly on their way out anyway.  
> > > > > > > > 
> > > > > > > > Let Me Know How It Goes
> > > > > > > > 
> > > > > > > > Karl
> > > > > > > >  
> > > > > > > > 
> > > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > >
> > > > > > > > > Hi Carl,
> > > > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > > > What number are the other ones you're refering to?
Are 
> > they 
> > > > also 
> > > > > > > > 2.2uF?
> > > > > > > > > Many thanks,Takis.
> > > > > > > > > 
> > > > > > > > >  
> > > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" 
<shire03@> 
> > wrote:
> > > > > > > > > >
> > > > > > > > > > Hello takisdamaschis,
> > > > > > > > > > 
> > > > > > > > > > When you say output capacitors, are you talking 
about 
> > the 
> > > > > > small 
> > > > > > > > 2.2uF
> > > > > > > > > > Cx49 at the edge of the voice board? There is one 
for 
> > > > each 
> > > > > > voice.
> > > > > > > > > > There is also one of these at the output of each 
VCO 
> > > > feeding 
> > > > > > the 
> > > > > > > > VCF
> > > > > > > > > > If these go you can have tuning problems. Also, 
try 
> > > > resetting 
> > > > > > the 
> > > > > > > > > > software.( hold sown clear and turn power On)
> > > > > > > > > > 
> > > > > > > > > > Karl
> > > > > > > > > > 
> > > > > > > > > > 
> > > > > > > > > > --- In 
xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > > >
> > > > > > > > > > > Hi everyone, my xpander seems to fail the VCO 
tune 
> > test 
> > > > > > > > randomly!some
> > > > > > > > > > > voices fail during one test and pass on the 
next! 
> > there 
> > > > is 
> > > > > > no
> > > > > > > > > > > cosistancy on the voices that fail,it can be 
any 
> > one of 
> > > > > > them!
> > > > > > > > Some
> > > > > > > > > > > times(rarely) the vco test passes! I have the 
same 
> > > > problem 
> > > > > > > > sometimes
> > > > > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > > > > I have totally rebuilt the power supply,changed 
the 
> > > > battery 
> > > > > > and 
> > > > > > > > output
> > > > > > > > > > > bypass capacitors!All currents measure right so 
> > this is 
> > > > not 
> > > > > > a 
> > > > > > > > voltage
> > > > > > > > > > > supply problem!
> > > > > > > > > > > The only other part I can think of is the DAC 
or 

> > maybe 
> > > > the 
> > > > > > > > Timer?
> > > > > > > > > > > Any thoughts?
> > > > > > > > > > > Takis.
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Karl,
I did the calibration procedure but unfortunately I can't get the DAC
trimmed down to 0volts!It keeps showing 4v(pin 6)!
Does that mean that the DAC is faulty?

--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:

>
> Hi Takis, 
> On page 34 of the Xpander service manual there is a DAC calibrtion 
> procedure. A different chip would need a calibration.
> What about the reference voltage? 
> 
> Karl
> 
> 
> 
> 
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi Karl,
> > I just got the new DAC! It's an HS3140C.I installed it
> > and.....nothing!Every test fails now instead of only some VCO's!
> > My original DAC is an MP7614KN, are these two incompatible and if so
> > why are they mentioned as both able to do the job?
> > Furtermore is there anything else I should have done when I replaced
> > the DAC that is not mentioned in the manual?
> > Thanks,Takis.
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > > Hi Takis,
> > > I measured the D805 in mine: 6.95 Vdc. I notice it's a diode in a 
> > > transistor package. This is a very accurate reference diode. It 
> > > should read at least 6.9 Volts. Pin 1 is not used. I measured 
> from 
> > > The left side of R856 ( just below it) to the middle leg of the 
> > > diode.  My schematics identify this as a 6.9 V Zener. If the one 
> in 
> > > yours shows a lower voltage than that, maybe this is causing the 
> > > tuning errors.  The diode may not be bad, something maybe 
> dragging it 
> > > down. I would take U815 out (turn Off first), then measure it 
> again. 
> > > If you can't get 6.9V out of that ref, I would replace it.  
> > > BTW about where is the adjustment trimmer pointing?
> > > 
> > > Karl
> > > 
> > > 
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > Hi Karl,
> > > > the voltmeter reads 6.38v!
> > > > Takis.
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > >
> > > > > Hi Takis,
> > > > > 
> > > > > What does the your voltmeter read when you measure the zener
> > > (D805)?
> > > > > I keep thinking it's something to do with this circuit.
> > > > > I am going to open mine up and see what I get.
> > > > > 
> > > > > Karl
> > > > > 
> > > > > 
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > <takisdamaschis@> wrote:
> > > > > >
> > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > > >
> > > > > > Hi Karl,
> > > > > > done everything you pointed out,no improvements!
> > > > > > Anything else you can think of before we go for the DAC?
> > > > > > Thanks,Takis.
> > > > > > 
> > > > > > 
> > > > > > > Hi Takis,
> > > > > > > > I also noticed that I get 3.79V at one of the pins of 
> U815 
> > > > > instead 
> > > > > > > > of 4.0V(+/- .05V) as the service manual points out!
> > > > > > > 
> > > > > > > Okay, lets look at D805, A zener diode which provides the 
> > > > > reference
> > > > > > > for the DAC.Measure this with a good voltmeter, it should 
> be 
> > > > > 6.9V. 
> > > > > > > Again, try reflowing the solder around this part and the 
> ref 
> > > > > circuit. 
> > > > > > > If you have a service 
> > > > > > > manual, Look at the circuit around U815 and reflow all 
> the 
> > > solder 
> > > > > > > around this part and the resistors capacitors etc...
> > > > > > > Try this and let me know.
> > > > > > > 
> > > > > > > Karl
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > <takisdamaschis@> wrote:
> > > > > > > >
> > > > > > > > Hi Karl,
> > > > > > > > I have gone and replaced all parts you suggested, re-
> seated 
> > > the 
> > > > > dac
> > > > > > > > and went over all solders!
> > > > > > > > No improvement, I keep getting the same problem!
> > > > > > > > I also noticed that I get 3.79V at one of the pins of 
> U815 
> > > > > instead 
> > > > > > > of
> > > > > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > > > > Anyway the good news is that I found a NOS dac ($150) 
> which 
> > > I 
> > > > > will 
> > > > > > > try
> > > > > > > > out as soon as it gets in(in a few days I hope).
> > > > > > > > I'll let you know!
> > > > > > > > Thanks,Takis.
> > > > > > > > 
> > > > > > > > 
> > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
> wrote:
> > > > > > > > >
> > > > > > > > > Hi Takis,
> > > > > > > > > The other caps are Cx33 and Cx37 with x being 
> 2,3,4,5,6,7 
> > > for 
> > > > > > > each 
> > > > > > > > > voice respectivly. And Yes they are the same 2.2uF 
> 50V 
> > > Make 
> > > > > sure 
> > > > > > > they 
> > > > > > > > > are 50V rating. and correct polarity (You probobly 
> knew 
> > > that)
> > > > > > > > > But before you replace those, try this.You are saying 
> you 
> > > are 
> > > > > > > having 
> > > > > > > > > problems with all the voices right?
> > > > > > > > > This points to the main DAC/Tuming circuit as you 
> have 
> > > > > already 
> > > > > > > > > guessed.
> > > > > > > > > 
> > > > > > > > > I would look closely at:
> > > > > > > > >  U811           The DAC        
> > > > > > > > >  U816,U805      Multiplexer    4051
> > > > > > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > > > > > >  U814           Analog Switch  4053 
> > > > > > > > > 
> > > > > > > > > Any of these parts failing could cause tuning 
> problems 
> > > like 
> > > > > you 
> > > > > > > > > describe.
> > > > > > > > > Now, before you replace them carfully pull them from 
> the 
> > > > > sockets 
> > > > > > > and 
> > > > > > > > > re-seat them. Sometimes corrosion on the socket/chip 
> lead 
> > > can 
> > > > > > > cause 
> > > > > > > > > a "not to good" connection. Also before I replaced 
> them I 
> > > > > would 
> > > > > > > > > reflow the solder on the bottom of the board, as bad 
> > > solder 
> > > > > > > joints 
> > > > > > > > > could also cause this.
> > > > > > > > > If this does not work replace em. All except the DAC 
> are 
> > > > > readily 
> > > > > > > > > available. I would wait till you replaced the other 
> chips 
> > > > > before 
> > > > > > > you 
> > > > > > > > > went searching for this DAC to see if any others are 
> the 
> > > > > cause. 
> > > > > > > If 
> > > > > > > > > one of the chips have failed, I would bet on the mux 
> or 
> > > > > analog 
> > > > > > > switch.
> > > > > > > > > It would not hurt to replace the capacitors I 
> mentioned 
> > > > > above, as 
> > > > > > > > > they are probobly on their way out anyway.  
> > > > > > > > > 
> > > > > > > > > Let Me Know How It Goes
> > > > > > > > > 
> > > > > > > > > Karl
> > > > > > > > >  
> > > > > > > > > 
> > > > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > >
> > > > > > > > > > Hi Carl,
> > > > > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > > > > What number are the other ones you're refering to?
> Are 
> > > they 
> > > > > also 
> > > > > > > > > 2.2uF?
> > > > > > > > > > Many thanks,Takis.
> > > > > > > > > > 
> > > > > > > > > >  
> > > > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" 
> <shire03@> 
> > > wrote:
> > > > > > > > > > >
> > > > > > > > > > > Hello takisdamaschis,
> > > > > > > > > > > 
> > > > > > > > > > > When you say output capacitors, are you talking 
> about 
> > > the 
> > > > > > > small 
> > > > > > > > > 2.2uF
> > > > > > > > > > > Cx49 at the edge of the voice board? There is one 
> for 
> > > > > each 
> > > > > > > voice.
> > > > > > > > > > > There is also one of these at the output of each 
> VCO 
> > > > > feeding 
> > > > > > > the 
> > > > > > > > > VCF
> > > > > > > > > > > If these go you can have tuning problems. Also, 
> try 
> > > > > resetting 
> > > > > > > the 
> > > > > > > > > > > software.( hold sown clear and turn power On)
> > > > > > > > > > > 
> > > > > > > > > > > Karl
> > > > > > > > > > > 
> > > > > > > > > > > 
> > > > > > > > > > > --- In 
> xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > Hi everyone, my xpander seems to fail the VCO 
> tune 
> > > test 
> > > > > > > > > randomly!some
> > > > > > > > > > > > voices fail during one test and pass on the 
> next! 
> > > there 
> > > > > is 
> > > > > > > no
> > > > > > > > > > > > cosistancy on the voices that fail,it can be 
> any 
> > > one of 
> > > > > > > them!
> > > > > > > > > Some
> > > > > > > > > > > > times(rarely) the vco test passes! I have the 
> same 
> > > > > problem 
> > > > > > > > > sometimes
> > > > > > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > > > > > I have totally rebuilt the power supply,changed 
> the 
> > > > > battery 
> > > > > > > and 
> > > > > > > > > output
> > > > > > > > > > > > bypass capacitors!All currents measure right so 
> > > this is 
> > > > > not 
> > > > > > > a 
> > > > > > > > > voltage
> > > > > > > > > > > > supply problem!
> > > > > > > > > > > > The only other part I can think of is the DAC 
> or 
> > > maybe 
> > > > > the 
> > > > > > > > > Timer?
> > > > > > > > > > > > Any thoughts?
> > > > > > > > > > > > Takis.
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Takis,
> Does that mean that the DAC is faulty?
Could Be, What happens if you put the old one back in, And check 
it's calibration, from pin 6 of U815?

Karl 


--- In xpantastic@yahoogroups.com, "takisdamaschis" 
<takisdamaschis@...> wrote:
>
> Hi Karl,
> I did the calibration procedure but unfortunately I can't get the 
DAC
> trimmed down to 0volts!It keeps showing 4v(pin 6)!
> Does that mean that the DAC is faulty?
> 
> --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> >
> > Hi Takis, 
> > On page 34 of the Xpander service manual there is a DAC 
calibrtion 
> > procedure. A different chip would need a calibration.
> > What about the reference voltage? 
> > 
> > Karl
> > 
> > 
> > 
> > 
> > 
> > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > <takisdamaschis@> wrote:
> > >
> > > Hi Karl,
> > > I just got the new DAC! It's an HS3140C.I installed it
> > > and.....nothing!Every test fails now instead of only some VCO's!
> > > My original DAC is an MP7614KN, are these two incompatible and 
if so
> > > why are they mentioned as both able to do the job?
> > > Furtermore is there anything else I should have done when I 
replaced
> > > the DAC that is not mentioned in the manual?
> > > Thanks,Takis.
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > >
> > > > Hi Takis,
> > > > I measured the D805 in mine: 6.95 Vdc. I notice it's a diode 
in a 
> > > > transistor package. This is a very accurate reference diode. 
It 
> > > > should read at least 6.9 Volts. Pin 1 is not used. I measured 
> > from 
> > > > The left side of R856 ( just below it) to the middle leg of 
the 
> > > > diode.  My schematics identify this as a 6.9 V Zener. If the 
one 
> > in 
> > > > yours shows a lower voltage than that, maybe this is causing 
the 
> > > > tuning errors.  The diode may not be bad, something maybe 
> > dragging it 
> > > > down. I would take U815 out (turn Off first), then measure it 
> > again. 
> > > > If you can't get 6.9V out of that ref, I would replace it.  
> > > > BTW about where is the adjustment trimmer pointing?
> > > > 
> > > > Karl
> > > > 
> > > > 
> > > > 
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > <takisdamaschis@> wrote:
> > > > >
> > > > > Hi Karl,
> > > > > the voltmeter reads 6.38v!
> > > > > Takis.
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > > >
> > > > > > Hi Takis,
> > > > > > 
> > > > > > What does the your voltmeter read when you measure the 
zener
> > > > (D805)?
> > > > > > I keep thinking it's something to do with this circuit.
> > > > > > I am going to open mine up and see what I get.
> > > > > > 
> > > > > > Karl
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > <takisdamaschis@> wrote:
> > > > > > >
> > > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
wrote:
> > > > > > > >
> > > > > > > Hi Karl,
> > > > > > > done everything you pointed out,no improvements!
> > > > > > > Anything else you can think of before we go for the DAC?
> > > > > > > Thanks,Takis.
> > > > > > > 
> > > > > > > 
> > > > > > > > Hi Takis,
> > > > > > > > > I also noticed that I get 3.79V at one of the pins 
of 
> > U815 
> > > > > > instead 
> > > > > > > > > of 4.0V(+/- .05V) as the service manual points out!
> > > > > > > > 
> > > > > > > > Okay, lets look at D805, A zener diode which provides 
the 
> > > > > > reference
> > > > > > > > for the DAC.Measure this with a good voltmeter, it 
should 
> > be 
> > > > > > 6.9V. 
> > > > > > > > Again, try reflowing the solder around this part and 
the 
> > ref 
> > > > > > circuit. 
> > > > > > > > If you have a service 
> > > > > > > > manual, Look at the circuit around U815 and reflow 
all 
> > the 
> > > > solder 
> > > > > > > > around this part and the resistors capacitors etc...
> > > > > > > > Try this and let me know.
> > > > > > > > 
> > > > > > > > Karl
> > > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > >
> > > > > > > > > Hi Karl,
> > > > > > > > > I have gone and replaced all parts you suggested, 
re-
> > seated 
> > > > the 
> > > > > > dac
> > > > > > > > > and went over all solders!
> > > > > > > > > No improvement, I keep getting the same problem!
> > > > > > > > > I also noticed that I get 3.79V at one of the pins 
of 
> > U815 
> > > > > > instead 
> > > > > > > > of
> > > > > > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > > > > > Anyway the good news is that I found a NOS dac 
($150) 
> > which 
> > > > I 
> > > > > > will 
> > > > > > > > try
> > > > > > > > > out as soon as it gets in(in a few days I hope).
> > > > > > > > > I'll let you know!
> > > > > > > > > Thanks,Takis.
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" 
<shire03@> 
> > wrote:
> > > > > > > > > >
> > > > > > > > > > Hi Takis,
> > > > > > > > > > The other caps are Cx33 and Cx37 with x being 
> > 2,3,4,5,6,7 
> > > > for 
> > > > > > > > each 
> > > > > > > > > > voice respectivly. And Yes they are the same 
2.2uF 
> > 50V 
> > > > Make 
> > > > > > sure 
> > > > > > > > they 
> > > > > > > > > > are 50V rating. and correct polarity (You 
probobly 
> > knew 
> > > > that)
> > > > > > > > > > But before you replace those, try this.You are 
saying 
> > you 
> > > > are 
> > > > > > > > having 
> > > > > > > > > > problems with all the voices right?
> > > > > > > > > > This points to the main DAC/Tuming circuit as you 
> > have 
> > > > > > already 
> > > > > > > > > > guessed.
> > > > > > > > > > 
> > > > > > > > > > I would look closely at:
> > > > > > > > > >  U811           The DAC        
> > > > > > > > > >  U816,U805      Multiplexer    4051
> > > > > > > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > > > > > > >  U814           Analog Switch  4053 
> > > > > > > > > > 
> > > > > > > > > > Any of these parts failing could cause tuning 
> > problems 
> > > > like 
> > > > > > you 
> > > > > > > > > > describe.
> > > > > > > > > > Now, before you replace them carfully pull them 
from 
> > the 
> > > > > > sockets 
> > > > > > > > and 
> > > > > > > > > > re-seat them. Sometimes corrosion on the 
socket/chip 
> > lead 
> > > > can 
> > > > > > > > cause 
> > > > > > > > > > a "not to good" connection. Also before I 
replaced 
> > them I 
> > > > > > would 
> > > > > > > > > > reflow the solder on the bottom of the board, as 
bad 
> > > > solder 
> > > > > > > > joints 
> > > > > > > > > > could also cause this.
> > > > > > > > > > If this does not work replace em. All except the 
DAC 
> > are 
> > > > > > readily 
> > > > > > > > > > available. I would wait till you replaced the 
other 
> > chips 
> > > > > > before 
> > > > > > > > you 
> > > > > > > > > > went searching for this DAC to see if any others 
are 
> > the 
> > > > > > cause. 
> > > > > > > > If 
> > > > > > > > > > one of the chips have failed, I would bet on the 
mux 
> > or 
> > > > > > analog 
> > > > > > > > switch.
> > > > > > > > > > It would not hurt to replace the capacitors I 
> > mentioned 
> > > > > > above, as 
> > > > > > > > > > they are probobly on their way out anyway.  
> > > > > > > > > > 
> > > > > > > > > > Let Me Know How It Goes
> > > > > > > > > > 
> > > > > > > > > > Karl
> > > > > > > > > >  
> > > > > > > > > > 
> > > > > > > > > > --- In 
xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > > >
> > > > > > > > > > > Hi Carl,
> > > > > > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > > > > > What number are the other ones you're refering 
to?
> > Are 
> > > > they 
> > > > > > also 
> > > > > > > > > > 2.2uF?
> > > > > > > > > > > Many thanks,Takis.
> > > > > > > > > > > 
> > > > > > > > > > >  
> > > > > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" 
> > <shire03@> 
> > > > wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > Hello takisdamaschis,
> > > > > > > > > > > > 
> > > > > > > > > > > > When you say output capacitors, are you 
talking 
> > about 
> > > > the 
> > > > > > > > small 
> > > > > > > > > > 2.2uF
> > > > > > > > > > > > Cx49 at the edge of the voice board? There is 
one 
> > for 
> > > > > > each 
> > > > > > > > voice.
> > > > > > > > > > > > There is also one of these at the output of 
each 
> > VCO 
> > > > > > feeding 
> > > > > > > > the 
> > > > > > > > > > VCF
> > > > > > > > > > > > If these go you can have tuning problems. 
Also, 
> > try 
> > > > > > resetting 
> > > > > > > > the 
> > > > > > > > > > > > software.( hold sown clear and turn power On)
> > > > > > > > > > > > 
> > > > > > > > > > > > Karl
> > > > > > > > > > > > 
> > > > > > > > > > > > 
> > > > > > > > > > > > --- In 
> > xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > Hi everyone, my xpander seems to fail the 
VCO 
> > tune 
> > > > test 
> > > > > > > > > > randomly!some
> > > > > > > > > > > > > voices fail during one test and pass on the 
> > next! 
> > > > there 
> > > > > > is 
> > > > > > > > no
> > > > > > > > > > > > > cosistancy on the voices that fail,it can 
be 
> > any 
> > > > one of 
> > > > > > > > them!
> > > > > > > > > > Some
> > > > > > > > > > > > > times(rarely) the vco test passes! I have 
the 
> > same 
> > > > > > problem 
> > > > > > > > > > sometimes
> > > > > > > > > > > > > with the Resonance and VCF but not as often!
> > > > > > > > > > > > > I have totally rebuilt the power 
supply,changed 
> > the 
> > > > > > battery 
> > > > > > > > and 
> > > > > > > > > > output
> > > > > > > > > > > > > bypass capacitors!All currents measure 
right so 
> > > > this is 
> > > > > > not 
> > > > > > > > a 
> > > > > > > > > > voltage
> > > > > > > > > > > > > supply problem!
> > > > > > > > > > > > > The only other part I can think of is the 
DAC 

> > or 
> > > > maybe 
> > > > > > the 
> > > > > > > > > > Timer?
> > > > > > > > > > > > > Any thoughts?
> > > > > > > > > > > > > Takis.
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Takis,

> My original DAC is an MP7614KN, are these two incompatible and 
> if so why are they mentioned as both able to do the job?
Looking at the data sheets These two parts( MP7614KN and HS3140C) are 
the same, and should be interchangable. If you have an output of 4 V 
on PIN 6  of the opamp(U815), then the op-amp could be at fault also.

Karl



--- In xpantastic@yahoogroups.com, "Karl" <shire03@...> wrote:
>
> Hi Takis,
> > Does that mean that the DAC is faulty?
> Could Be, What happens if you put the old one back in, And check 
> it's calibration, from pin 6 of U815?
> 
> Karl 
> 
> 
> --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> <takisdamaschis@> wrote:
> >
> > Hi Karl,
> > I did the calibration procedure but unfortunately I can't get the 
> DAC
> > trimmed down to 0volts!It keeps showing 4v(pin 6)!
> > Does that mean that the DAC is faulty?
> > 
> > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > >
> > > Hi Takis, 
> > > On page 34 of the Xpander service manual there is a DAC 
> calibrtion 
> > > procedure. A different chip would need a calibration.
> > > What about the reference voltage? 
> > > 
> > > Karl
> > > 
> > > 
> > > 
> > > 
> > > 
> > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > <takisdamaschis@> wrote:
> > > >
> > > > Hi Karl,
> > > > I just got the new DAC! It's an HS3140C.I installed it
> > > > and.....nothing!Every test fails now instead of only some 
VCO's!
> > > > My original DAC is an MP7614KN, are these two incompatible 
and 
> if so
> > > > why are they mentioned as both able to do the job?
> > > > Furtermore is there anything else I should have done when I 
> replaced
> > > > the DAC that is not mentioned in the manual?
> > > > Thanks,Takis.
> > > > 
> > > > 
> > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> wrote:
> > > > >
> > > > > Hi Takis,
> > > > > I measured the D805 in mine: 6.95 Vdc. I notice it's a 
diode 
> in a 
> > > > > transistor package. This is a very accurate reference 
diode. 
> It 
> > > > > should read at least 6.9 Volts. Pin 1 is not used. I 
measured 
> > > from 
> > > > > The left side of R856 ( just below it) to the middle leg of 
> the 
> > > > > diode.  My schematics identify this as a 6.9 V Zener. If 
the 
> one 
> > > in 
> > > > > yours shows a lower voltage than that, maybe this is 
causing 
> the 
> > > > > tuning errors.  The diode may not be bad, something maybe 
> > > dragging it 
> > > > > down. I would take U815 out (turn Off first), then measure 
it 
> > > again. 
> > > > > If you can't get 6.9V out of that ref, I would replace it.  
> > > > > BTW about where is the adjustment trimmer pointing?
> > > > > 
> > > > > Karl
> > > > > 
> > > > > 
> > > > > 
> > > > > 
> > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > <takisdamaschis@> wrote:
> > > > > >
> > > > > > Hi Karl,
> > > > > > the voltmeter reads 6.38v!
> > > > > > Takis.
> > > > > > 
> > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
wrote:
> > > > > > >
> > > > > > > Hi Takis,
> > > > > > > 
> > > > > > > What does the your voltmeter read when you measure the 
> zener
> > > > > (D805)?
> > > > > > > I keep thinking it's something to do with this circuit.
> > > > > > > I am going to open mine up and see what I get.
> > > > > > > 
> > > > > > > Karl
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > <takisdamaschis@> wrote:
> > > > > > > >
> > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" <shire03@> 
> wrote:
> > > > > > > > >
> > > > > > > > Hi Karl,
> > > > > > > > done everything you pointed out,no improvements!
> > > > > > > > Anything else you can think of before we go for the 
DAC?
> > > > > > > > Thanks,Takis.
> > > > > > > > 
> > > > > > > > 
> > > > > > > > > Hi Takis,
> > > > > > > > > > I also noticed that I get 3.79V at one of the 
pins 
> of 
> > > U815 
> > > > > > > instead 
> > > > > > > > > > of 4.0V(+/- .05V) as the service manual points 
out!
> > > > > > > > > 
> > > > > > > > > Okay, lets look at D805, A zener diode which 
provides 
> the 
> > > > > > > reference
> > > > > > > > > for the DAC.Measure this with a good voltmeter, it 
> should 
> > > be 
> > > > > > > 6.9V. 
> > > > > > > > > Again, try reflowing the solder around this part 
and 
> the 
> > > ref 
> > > > > > > circuit. 
> > > > > > > > > If you have a service 
> > > > > > > > > manual, Look at the circuit around U815 and reflow 
> all 
> > > the 
> > > > > solder 
> > > > > > > > > around this part and the resistors capacitors etc...
> > > > > > > > > Try this and let me know.
> > > > > > > > > 
> > > > > > > > > Karl
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > --- In xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > >
> > > > > > > > > > Hi Karl,
> > > > > > > > > > I have gone and replaced all parts you suggested, 
> re-
> > > seated 
> > > > > the 
> > > > > > > dac
> > > > > > > > > > and went over all solders!
> > > > > > > > > > No improvement, I keep getting the same problem!
> > > > > > > > > > I also noticed that I get 3.79V at one of the 
pins 
> of 
> > > U815 
> > > > > > > instead 
> > > > > > > > > of
> > > > > > > > > > 4.0V(+/- .05V) as the service manual points out!
> > > > > > > > > > Anyway the good news is that I found a NOS dac 
> ($150) 
> > > which 
> > > > > I 
> > > > > > > will 
> > > > > > > > > try
> > > > > > > > > > out as soon as it gets in(in a few days I hope).
> > > > > > > > > > I'll let you know!
> > > > > > > > > > Thanks,Takis.
> > > > > > > > > > 
> > > > > > > > > > 
> > > > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" 
> <shire03@> 
> > > wrote:
> > > > > > > > > > >
> > > > > > > > > > > Hi Takis,
> > > > > > > > > > > The other caps are Cx33 and Cx37 with x being 
> > > 2,3,4,5,6,7 
> > > > > for 
> > > > > > > > > each 
> > > > > > > > > > > voice respectivly. And Yes they are the same 
> 2.2uF 
> > > 50V 
> > > > > Make 
> > > > > > > sure 
> > > > > > > > > they 
> > > > > > > > > > > are 50V rating. and correct polarity (You 
> probobly 
> > > knew 
> > > > > that)
> > > > > > > > > > > But before you replace those, try this.You are 
> saying 
> > > you 
> > > > > are 
> > > > > > > > > having 
> > > > > > > > > > > problems with all the voices right?
> > > > > > > > > > > This points to the main DAC/Tuming circuit as 
you 
> > > have 
> > > > > > > already 
> > > > > > > > > > > guessed.
> > > > > > > > > > > 
> > > > > > > > > > > I would look closely at:
> > > > > > > > > > >  U811           The DAC        
> > > > > > > > > > >  U816,U805      Multiplexer    4051
> > > > > > > > > > >  U812,U815,U813 Op Amps        TLO81,TLO84,TLO81
> > > > > > > > > > >  U814           Analog Switch  4053 
> > > > > > > > > > > 
> > > > > > > > > > > Any of these parts failing could cause tuning 
> > > problems 
> > > > > like 
> > > > > > > you 
> > > > > > > > > > > describe.
> > > > > > > > > > > Now, before you replace them carfully pull them 
> from 
> > > the 
> > > > > > > sockets 
> > > > > > > > > and 
> > > > > > > > > > > re-seat them. Sometimes corrosion on the 
> socket/chip 
> > > lead 
> > > > > can 
> > > > > > > > > cause 
> > > > > > > > > > > a "not to good" connection. Also before I 
> replaced 
> > > them I 
> > > > > > > would 
> > > > > > > > > > > reflow the solder on the bottom of the board, 
as 
> bad 
> > > > > solder 
> > > > > > > > > joints 
> > > > > > > > > > > could also cause this.
> > > > > > > > > > > If this does not work replace em. All except 
the 
> DAC 
> > > are 
> > > > > > > readily 
> > > > > > > > > > > available. I would wait till you replaced the 
> other 
> > > chips 
> > > > > > > before 
> > > > > > > > > you 
> > > > > > > > > > > went searching for this DAC to see if any 
others 
> are 
> > > the 
> > > > > > > cause. 
> > > > > > > > > If 
> > > > > > > > > > > one of the chips have failed, I would bet on 
the 
> mux 
> > > or 
> > > > > > > analog 
> > > > > > > > > switch.
> > > > > > > > > > > It would not hurt to replace the capacitors I 
> > > mentioned 
> > > > > > > above, as 
> > > > > > > > > > > they are probobly on their way out anyway.  
> > > > > > > > > > > 
> > > > > > > > > > > Let Me Know How It Goes
> > > > > > > > > > > 
> > > > > > > > > > > Karl
> > > > > > > > > > >  
> > > > > > > > > > > 
> > > > > > > > > > > --- In 
> xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > Hi Carl,
> > > > > > > > > > > > yes I replaced all six Cx49 capacitors!
> > > > > > > > > > > > What number are the other ones you're 
refering 
> to?
> > > Are 
> > > > > they 
> > > > > > > also 
> > > > > > > > > > > 2.2uF?
> > > > > > > > > > > > Many thanks,Takis.
> > > > > > > > > > > > 
> > > > > > > > > > > >  
> > > > > > > > > > > > --- In xpantastic@yahoogroups.com, "Karl" 
> > > <shire03@> 
> > > > > wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > Hello takisdamaschis,
> > > > > > > > > > > > > 
> > > > > > > > > > > > > When you say output capacitors, are you 
> talking 
> > > about 
> > > > > the 
> > > > > > > > > small 
> > > > > > > > > > > 2.2uF
> > > > > > > > > > > > > Cx49 at the edge of the voice board? There 
is 
> one 
> > > for 
> > > > > > > each 
> > > > > > > > > voice.
> > > > > > > > > > > > > There is also one of these at the output of 
> each 
> > > VCO 
> > > > > > > feeding 
> > > > > > > > > the 
> > > > > > > > > > > VCF
> > > > > > > > > > > > > If these go you can have tuning problems. 
> Also, 
> > > try 
> > > > > > > resetting 
> > > > > > > > > the 
> > > > > > > > > > > > > software.( hold sown clear and turn power 
On)
> > > > > > > > > > > > > 
> > > > > > > > > > > > > Karl
> > > > > > > > > > > > > 
> > > > > > > > > > > > > 
> > > > > > > > > > > > > --- In 
> > > xpantastic@yahoogroups.com, "takisdamaschis" 
> > > > > > > > > > > > > <takisdamaschis@> wrote:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Hi everyone, my xpander seems to fail the 
> VCO 
> > > tune 
> > > > > test 
> > > > > > > > > > > randomly!some
> > > > > > > > > > > > > > voices fail during one test and pass on 
the 
> > > next! 
> > > > > there 
> > > > > > > is 
> > > > > > > > > no
> > > > > > > > > > > > > > cosistancy on the voices that fail,it can 
> be 
> > > any 
> > > > > one of 
> > > > > > > > > them!
> > > > > > > > > > > Some
> > > > > > > > > > > > > > times(rarely) the vco test passes! I have 
> the 
> > > same 
> > > > > > > problem 
> > > > > > > > > > > sometimes
> > > > > > > > > > > > > > with the Resonance and VCF but not as 
often!

> > > > > > > > > > > > > > I have totally rebuilt the power 
> supply,changed 
> > > the 
> > > > > > > battery 
> > > > > > > > > and 
> > > > > > > > > > > output
> > > > > > > > > > > > > > bypass capacitors!All currents measure 
> right so 
> > > > > this is 
> > > > > > > not 
> > > > > > > > > a 
> > > > > > > > > > > voltage
> > > > > > > > > > > > > > supply problem!
> > > > > > > > > > > > > > The only other part I can think of is the 
> DAC 
> > > or 
> > > > > maybe 
> > > > > > > the 
> > > > > > > > > > > Timer?
> > > > > > > > > > > > > > Any thoughts?
> > > > > > > > > > > > > > Takis.
> > > > > > > > > > > > > >
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