Xpantastic!

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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