Re: Q*bert sound board repair

I am working on the S&S board on the bench, no CPU at all.

Turn the board on no sound.
Press test button no sound

Checked cpu for reset and address / data lines. All look reasonable.

If I watch the select lines for the sound latches (U7 pin 4) and hit the
test button I get some activity and I get data out.

I can't scope the output of the DAC as it is a current driving DAC, but if I
scope pin 6 of the amp at U22 I am getting around 1.2vdc no change during
activity above.

I would suspect a bad amp but I checked another board and the output was
about 10vdc when idle. Need to lift the pin and see if the amp section is
pulling it low. Also the DAC is getting warm so it could be blown.

Is there a source for the DACs? I can build up the daughter board to
replace the amp if needed. Anyone have the required mods for the power
supply board to support the later rev amp?

Something I noticed when comparing this board with a known working (from
Q*Bert Qubes) is that the bad board (which had no roms, now has reactor
roms) is missing some parts in the amp section. The appear to have never
been loaded.

R 18, 21, 22
and C 37

Looking at the schematic this appears to be leaving the - side of the amp
floating as pin 8 should be tied to the output (pin 10) through R21 with R22
and C37 providing a ground reference (I think).

Not very good with audio circuits so could be way off base.

Anyone seen this before?

If the amp and dac's are blown is the board considered a write off? Don't
figure a replacement with at least a bit more working should be that hard to
find.

----- Original Message -----
From: "Tom McClintock" <tomm@mgcap.com>
To: <rasterlist@synthcom.com>
Sent: Monday, August 13, 2001 5:34 AM
Subject: Re: RASTER: Q*bert sound board repair

> Thanks Joe :)
>
> David, you might check the 74LS377PC on the main CPU (in the audio output
> section of the CPU). It is socketed and sits inline with the signals to
the
> sound board.
>
> BTW, the dip switches on the sound board don't do anything. They were
installed
> to work with the Gottlieb factory test fixture and (someone correct me if
I'm
> wrong) a few Gottlieb pinballs that shared the sound board.
>
> tm
>
> "Magiera, Joe (AIT)" wrote:
>
> > Roy "Chumblespuz" has a good Q*bert sound repair guide. His web page
> > appears to be unavailable, but it has been copied to:
> >
http://www.ionpool.net/arcade/gottlieb/technical/QBert_sound_tech/qbert_soun
> > d.html
> >
<http://www.ionpool.net/arcade/gottlieb/technical/QBert_sound_tech/qbert_sou
> > nd.html> , which is part of Tom McClintock's excellent Gottlieb portion
of
> > his web page. Tom has lot's of other good Gottlieb tech advice, it's
at:
> > http://www.ionpool.net/arcade/gottlieb/index.html
> > <http://www.ionpool.net/arcade/gottlieb/index.html> , his main page is:
> > http://www.ionpool.net <http://www.ionpool.net>
> >
> > If those pages DON'T help you fix your Q*bert sound, I suspect both Tom
and
> > Roy would be interested in hearing from you to further diagnose (and
then
> > add to their troubleshooting info once finally fixed). I would too, as
my
> > Q*bert sound is out too.
> >
> > See you at CA Extreme (I hope!).
> >
> > Joe
> >
> > joe.magiera@ameritech.com <mailto:joe.magiera@ameritech.com>
> >
> > -----Original Message-----
> > From: David Shoemaker [mailto:davids@oz.net]
> > Sent: Monday, August 13, 2001 3:35 AM
> > To: rasterlist@synthcom.com
> > Subject: RASTER: Q*bert sound board repair
> >
> > Anyone have a repair guide for these?
> >
> > I have one that gives no sound on power up and no sound on hitting the
test
> > button.
> >
> > CPU / 6532 / roms are all checked good.
> >
> > Anyone know what the switch bank on the board does?
> >
> > Thanks,
> > David
>
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>
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