Quoted from blownfuse:
I'll give you a general list of common things to look at that could cause a sound board malfunction (no sound), they should be checked and working perfect before going into troubleshooting the sound board (if needed). If any of these connections are bad or the voltages are off, diagnosis of the sound board will be a waste of time.
1. Check *all voltages* at the sound board, make sure they're present and correct.
A. Check the F8 fuse (1A slo-blo) for the sound board with a meter, you may have blown it when you messed with the pot.
B. Check the A2J1-5/6 (5VDC) connection for cracks around the header pins. This is where the sound board gets it's 5VDC from, it's not uncommon for this issue to be there.
2. Check the Z13 IC (7404) on the driver board for a bad gate, if one of these output signals isn't high at start up, the sound board won't run.
The sound board should run independently of the CPU during attract mode, if you get the sounds working, you still could have issues with the A1J4 to A3J1 connector for controlled sound lines (1, 2, 4 & 8 sometimes take a "hit" from alkaline damage). Maybe you'll get lucky and the sound board works. Keep in mind that there may be other issues to fix since this game probably hasn't been working in a while.
System 80, not just a job, it's an adventure
Sorry I have not posted back. I have been super busy with the holidays and I have been building a galaga multicade for my 8 year old.
I checked the connectors and the double edged one had some corrosion. I do not have the correct connector pins to rebuild it and I am going to order them from GPE as soon as he reopens.
I am not super familiar with checking the IC (7404). It appears to have some corrosion on it but not battery leakage. More of an orange color like flux. They cost like a dollar at GPE so I will just pick up a couple when I order.
I do not have a manual for the game but have been looking at pinwiki's overview of system 80 games. That being said I am not sure where all to check the voltages on the sound board. I can check the input voltage a pin 1 on the connector but do not know where to check form there.