Williams System 9 sound problem

[48]

G'day all,
Am repairing a 1985 Williams Comet. Got it up and running however NO SOUND. Has a hum in the speakers but no boot-up tone, nothing. The only change to the slight hum is a change in frequency as the attract lights run.
There is precious little info for these things even Marvins site seems to concentrate on Sys11, which has the entire sound setup in one, where sys9 has a seperate speech board and the rest of the sound on the main.
Have checked everything I can think of speakers OK volume pots OK wiring OK.
Speech board is powered up too.
Anyone had any experience with sys9 be able to help me out?
Thanks.

[ddstoys]

Welcome to AP i have a comet but have not had to deal with any sound issues and from your post sounds like im glad it worked if there is anything i can test on mine to help you out let em know 

[goodolddays]

  to AP.

Not sure if this info will help ?

http://home.scarlet.be/~fb054529/will9/ewill9.htm

Cheers
Dave

[48]

Thanks guys, replies greatly appreciated.
Worried that the answer looks rather complicated, more to learn I suppose!
Perhaps I should have stuck to my EM's!

[goodolddays]

Gday 48.

I noticed this comment in Marvin's guide
"The sound portion of the sound card is built-in to the system9 CPU board (and the CPU 2764 or 27128 at U49 position is used for the sound ROM). " ...

so just wondering is that CPU at U49 socketed ?? if so.. have you tried reseating it ? .. are the legs on it corroded ?

[48]

Yes its a plug in. No corrosion on it, took it out and re-seated it just in case, unfortunately it didn't work.
Thanks for the suggestion though.
Cheers.

[48]

FINALLY got it sorted! 
Appears that battery corrosion at some time had gotten behind one of the IC sockets.
Nothing to see when IC removed, no sign of anything on rear of board or front really.
But it was enough to screw something up.
Any way I now have a working Comet.
Funny bloody machine to listen to.
Anyone else who has one will know what I mean.
Thanks to all who helped in this and my other thread on Sys9 sound.
Cheers,

[ddstoys]

 I love leaving it in attract mode at night when the clown laughs people shit themselves lol

[48]

Thanks for the warning Daniel,
The missus says you are about an hour late with it
And I had the speech card up loud sorting it!