Xpantastic!

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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