So Flash Gordon I'm working on has speech but no sound. Caps are fresh, and I've replaced the pots.
The J1 connector and wires were heavily hacked and at one point I was able to get game sounds working by wiggling the wires connected to J1 a bit, but never for long - usually just had static.
By "game sounds", I mean the ones triggered by in game switches and flashers. If I press the self-test button on the Squawk an Talk board all the speech works and also the sound effect at the end of the test, though I believe that sound is MPU generated and not part of the sound circuit that isn't working as noted below:
Source: http://www.pinrepair.com/bally/squawk.htm
"S&T Sound Generation.
Sound generation/special audio effects are handled in two ways: 1 - A General Instruments AY3-8912 PSG IC fitted in U12 under control of the PIA at U11 (which is in turn controlled by the S+T 680x) generates basic square wave tones, noise and sound shaping envelopes that control the output
amplitude to the amplifier circuits. These tones are limited in scope (how many different square waves can you have?). "
So I replaced the J1 connector and cleaned up the wires. Now I get nothing at all in terms of sound. On startup there is a clicking sound like someone tapping on a microphone. Though the self-test work fine still.
I swapped in a known working U11 PIA chip and no difference. I don't have a spare U12 though so will need to order one if I don't find another issue.
I've been testing the connections between J1 pins and their various landing pins on other boards to verify my connector wiring, and I've run into a few that are referenced in the schematic that I can't figure out where they are (shown with "?" next to them in the pic below).
SAndTJ1Schematic (resized).JPG
J1 P9 -> A3J3-5 ?
J1 P10 -> A3J3-12 ?
J1 P15 -> A3J3-23 and A2J3-19 ? (I discovered that A2J4-2 has continuity with J1 P15 though)
Does anyone know where these reside? I'd just like to know 100% that the connector is solid before I go and order a new U12 (AY3-8912 PSG IC). Other suggestions are also welcomed.