I was working on a Macintosh Classic II which had an interesting fault. It was the second time I had fixed it on one and thankfully had notes from the first time.
When powering on the system you have either no sound or distorted sound. Pressing reset continuously makes it get “better” but never right.
Check the resistance between pin 4 and 5 on the 34119, it should be 75k. If it’s say 1M or more, you have a bad connection. Likely due to corrosion. Add a jumper wire to fix.