I realise that given the age of this thread that the problem has most likely been solved, but as I've found reading old threads to be helpful and as I had a similar problem with my Williams sound board I thought I'd document how I fixed mine. Someone may find this useful in the future?
Schematics can be found here;
http://www.pinrepair.com/sys37/s67snd.pdfOn mine the test button produced the full compliment of sound and speech, so this proves most of the board is working. ie power supply, pia, dac, amp, speech module. So the area in question is the sound select inputs from the driver board.
The driver board sees and selects sounds in the same way that physical solenoids are driven ie by grounding an output. The selected sound is achieved by putting the required value into port B of the sound card pia IC10. IC5 and IC7 buffer the signal from the driver board down to cmos levels and pin 13 of IC6 acts to drive the pia interrupt CB1.
Grounding each of the sound select inputs on J3 and using a logic probe allows the sound select logic to be analysed. Hooking up a speaker and pot to J2 and J4 will allow you to hear any sounds produced.
In my case IC7 had failed and one of the gate outputs had failed to hi impedance. Replacing this chip and using a high quality socket solved my problem. I also noted that IC5 had been socketed in a previous repair, so perhaps theses chips are susceptible to failure.
cheers,
David.
