Hola-
Replaced some CMOS with no result, finally had success with a new 4558
at IC19.
Thanks for the help -- this didn't used to be so difficult, but with 4
to 6 repairs going at once (and more on the way), it's difficult to
focus like I'm supposed to.
Looking forward to a break soon....
Thanks again.
~G
Andrew Jury wrote:
>
>
> Hi,
>
> Probably some issues in the anti-log circuit. To verify note the
> voltages at
> IC31 pin 3. Try a C in each octave. This voltage should ramp up in a
> linear
> fashion as the frequency increases. If not try replacing IC30 (you have
> replaced IC31 already, right?). Also take a look at IC19. The A side of it
> is a precise voltage reference (output should be 9V). If this is wrong you
> might be in trouble. Also make sure that if you replaced Q12 that the new
> device is a matched pair and thermally bonded. Two BC549s glued together
> just won¹t cut it, but you probably know that!
>
> Cheers,
> Andy
>
> On 30/04/2012 18:36, "klosmon" <klosmon@sbcglobal.net
> <mailto:klosmon%40sbcglobal.net>> wrote:
>
> >
> >
> >
> >
> >
> > Hello-
> > I'm working on an older version voice board (with the 396 add-on board)
> > that won't tune.
> > The six oscillators can be tuned to match at the low points & high
> > points, but there's no way to tune them to play anything like a
> > half-tone scale.
> >
> > I've tried the usual (replace the optoisolator, replace the 4051,
> > replace the dual transistor, replace the TL071 opamp), but nothing
> helps.
> >
> > Any ideas where else I should be looking?
> >
> > Thanks.
> >
> > ~G
> >
> >
> >
> >
>
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>
>
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