Re: 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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