Batboard

I have a VHF CP200 with only a trace of internal mic or external mic audio. There is mic bias on mics. PL and MDC modulation is normal. Increasing mic gain or bandwidth does not increase mic audio. Is this a common problem and is there a known cure?

Very likely a bad speaker/mic socket, or broken solder connection going to it.

I second the mic jack. The design is terrible. I fixed every one we sold I think. They shouldn't even allow mics on those things. resolder the jack if the board didnt get screwed up and pulled a pad off.

The Mic jack assy. is a real pain to replace.
The 'hidden' contact pads in front, as well as the rear, are a nuisance to desolder.
Pad lifting is the #1 problem if a cold joint is lifted, resulting in tearing of the trace.

The CP185 also has similar issues.
One wrong move, and you can tear off a pad, then spend hours tracing the point so it can be hard wired to get around the issue.
I prefer to fully heat one joint, use a dental pick as I heat and then lift each pad separately, then wick it so it will not reattach when you move to the next pad.
These assemblies are not 'friendly' to casual desoldering, and speed, slow down, use caution and care, and work slowly.