tech: Sega Pengo Sound - external volume control

[rgvac2]

Hi

I have an original Sega Pengo PCB, when I don't connect the 12v the game
boots and plays fine, just without the sound.

When I connect the 12v it doesn't boot at all. If the 12v is only for the
power amp, why doesn't the game boot?.

I notice that the game originally came with an external volume control. I
left this open, which I presume would mean no volume, but the game should
boot!.

If I close these pins it should be full volume, does this volume control
effect the booting of the PCB?

Thanks

Rob

[Mark (UK)]

Hiya!

An original Pengo PCB should have a sound pot onboard:

http://www.leopardcats.com/oddities/pengojrpac.jpg

(That's a Jr Pacman hack, but it's a genuine Pengo underneath - it's the
only photo I had to hand)

There may have been an external volume pot in the cab, connected to pin
X, to override the internal pot.

As for the booting, I've looked over the schems, and it does appear that
the +12v only goes to the amp. I would try removing the amp chip, then
see if it boots with the 12v connected. If not, there may be a hairline
short somewhere affecting the logic.

If it does boot with the amp removed, it may well be a duff amp. The amp
is connected indirectly to the logic of the CPU, so it may be
upsetting it.

Good luck! Yours, Mark.

[Iain Odlin]

On Mon, 3 Nov 2003 19:45:37 +0000 (UTC), "Mark (UK)"
<jumbos...@btopenworld.com> wrote:

>Hiya!
>
>An original Pengo PCB should have a sound pot onboard:
>
>http://www.leopardcats.com/oddities/pengojrpac.jpg
>
>(That's a Jr Pacman hack, but it's a genuine Pengo underneath - it's the
>only photo I had to hand)
>
>There may have been an external volume pot in the cab, connected to pin
>X, to override the internal pot.

It doesn't actually override it. It kind of gives you a range of volumes
around the volume you set on the PCB. It's a bit strange.

-Iain