Odd System 6 Sound behavior

[Randy R.]

In fixing up a 'Scorpion' (Williams System 6), I noticed the machine
didn't have the sound I expected. It made electronic chime noises
when something was hit, but no background noise. The backgound
'music' played when the sound board diagnostic switch was pressed, but
not in game mode.

Then I noticed the curious toggle switch on the soundboard. The
function of this switch is not mentioed in any of the manuals or
Clay's guides. So may natural thought..."let's see what this does!".

It seemed to do the trick, as changing this switch yielded the
expected background sound. However as soon as the ball hit something
(i.e. activating another sound), the machine completely locks
up...displays and all controlled lamps go out, flippers stop working,
etc, though the GI stays on. No fuses blown, and within a couple of
on/off cycles the machine will re-start normally.

I did some searching here on RGP and find that this toggle switch
chooses between "artificial chime" sound effects and full "electronic"
sound effects.

Ok, but what in the world is going on such that in chime mode the
machine plays and sounds just fine, but in electronic sound mode it
completely locks up? All of the sound drive circuits seem fine
(they're needed for chime mode anyways) and the sound plans in
diagnostic mode so I'm assuming this means the sound ROM is ok. I've
just never seen a case where the sound board causes the whole system
to fail, and then only when it's set in a specific mode.

Has anyone seen this happen before, or have any idea where on the
sound board to look for the trouble? Has me puzzled....

- Randy

[Randy R.]

Just as a follow-up to this prior posting.

I went ahead and replaced the sound ROM on the sound board as well as
the associated Scanbe socket.

I also replaced the 6 electrolytic capacitors on the sound board.

With this done, the sound board is working correctly! Now since I
did both sets of changes at the same time I don't know if one of the
other was really the culprit, but replacing all the caps seemed to be
on the safe side.

Also, the *only* place I was able to find 12,000 MFD 25V axial
electrolytic capacitors was via Great Plains Electronics. All the
others I was able to find via Mouser.

- Randy