No sound (volume, speaker pins* and audio fuses checked), no hint of any audio noise. Awhile back I started getting a loud audio squawk when the pin was initially powered up, but I thought nothing of it since it was similar to what was common on some WPCs when powered down. Now months later all at once there is no sound at all. I am not sure where to start my diagnosis (audio problems don't seem to be very common on WPC pins and I had never heard that the shock wave to the audio amp I am hearing was so loud it could damage anything), so I am asking for any suggestions to no sound? **My Pinside search skills are not that great, I only saw a thread on replacing capacitors, but my feeling is that sudden failure of a WPC pin with decent audio would not be capacitors (depending on what the capacitors are used for), and is related to the audio board, probably the analog amps.

Thanks!
*edit to add that I did not check for a broken speaker wire, I initially only checked that connectors 505 and 504 were inserted solid (speaker pins). I read later that the three speakers are connected in series, so a broken wire anywhere between the speakers kills all sound. This is obvious from the fact that only two wires are involved in connectors 505 and 504, but I did not realize to check for broken wires along the chain.
**BTW, I found this additional info from a Google search that gave me good references to Pinside forum topics that seemed to be better targeted for my needs than Pinside's forum search tool.

Thanks U1 was it. I looked at the sound board schematics for U1 in order to sort out the circuit; checked the +/- voltages on U1 pins #3 & #5 (good) then checked the sound board for low voltage audio input into U1 by tapping onto U1 leads #1 & #2 and listening for a signal using earbuds. Now I just need to go downtown and get a new LM1875 IC from our local good-old boy electronics shop that I need to frequent more often anyhow.