Problem Galaxian bootleg - missing/bad sound effects

[cools]

This Galaxian bootleg has some audio problems - the background drone sound should be pulsing, and player shot and death noises are missing.

I've recapped it which has cleaned the sound up a little but not fixed the problems.

Any ideas what I could look at next? I don't really want to invest much more into fixing it when a 60-in-1 will do basically the same job for what I need.

https://imgur.com/a/C2ycypO

 

[Georgian2]

One 4066 could be faulty here. Can't remeber the exact position.

 

[cools]

Can only find the one!

 

[cools]

Just discovered the troubleshooting manual and it says the same thing as you. Will piggybacking a good chip be a reasonable test?

 

[cliff_poole]

A crystal earpiece is a good cheap tool for this sort of job. Tie one side to ground and use the other as a probe. You'll be able to hear if there is sound at the inputs of the 4066. Use a logic probe to check if the 4066 is being triggered.