Re: Q*bert sound board repair

I was looking at another sound board I had, I think I figured out the
missing parts. The board had the daughter card on it and the parts I
referenced below were not loaded. So it looks like this board used to have
the replacement amp but it was removed and the LM379 was installed (before I
got the board). But the other parts were not loaded. As a result the amp
section is not working properly.

I will pickup the misc I need today and load those parts tonight and let you
know what I find out.

----- Original Message -----
From: "Tom McClintock" <tomm@mgcap.com>
To: <rasterlist@synthcom.com>
Sent: Tuesday, August 14, 2001 5:54 AM
Subject: Re: RASTER: Q*bert sound board repair

> David,
>
> David Shoemaker wrote:
>
> > 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?
>
> Here's the information on the PS boards:
> http://www.ionpool.net/arcade/gottlieb/technical/power.html
>
> Just remember, if you lower the voltage on the power supply board, you
will need
> to find a lower voltage knocker coil. You could always replace the LM379
audio
> amplifier from Bob Roberts if needed, and then just replace the original
1N5363B
> zener diode that was rated for 30 volts. It is a good idea to remove it
and
> replace it with a five-watt zener diode rated for 25 volts or 24 volts.
> Alternatively you could use a 27volt, 10-watt zener diode.
>
> The AD7528 DAC is still in production and you can presumably order
directly from
> Analog Devices:
> http://products.analog.com/products/genericInfo.asp?product=AD7528
>
> I've got the datasheet on my site as well, but I would check the amp
first.
>
>
>
> > 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
>
> Hmmm, I'd be interested in seeing a picture of this PS board. It doesn't
seem to
> match up with the schematics...
>
>
> > 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.
>
> Definitely NOT a write off. Keep the board as it as the Votrax SC-01 on it
(not
> to mention the other chips). If someone wants to figure out how to use the
> Gottlieb factory sound test ROMs that I have on the site, please feel
free!
>
>
> tm
>
>
>
> > ----- 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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