Although I replaced this module I still am interested in fixing it.

The top output have a quiet oscillator sound, probably the driver. There is no additional digital noise. The bottom works as it should.

I have tried replacing the schmitt trigger, switching them etc. This has not worked. I also have replaced the jacks.

Bypassing the input jack as seen here: http://oldsocksandnewtoys.blogspot.com/2009/01/doepfer-117-mod.html

This allows me to run signal in and hear it with clocked digital noise as well, so it sort of sounds like a bit reducer. Cool but not correct.

What other parts should I replace to see if I can get this to work

Thanks