Problem with Keeley C4 compressor

[rutledj]

I have one of these I purchased off Ebay. It does not work in the sense that the sustain knob seems to do nothing. You can get sound out and the level and clip knob affect the output but not much else.  I replaced the chip and transistors but it didn't change anything. Any suggestions on what to look at next?

Thanks
Rut

[Ben Lyman]

If you have a DMM, take some volt readings, I'm sure someone here will spot the issue right away. If you pop a link up here to the schematic along with those readings, it will increase your chances of that someone helping.
Good luck 

[rutledj]

Thanks. I'll try to do that tonight after work. The schematic is just one I've found searching the internet. Not sure it is completely accurate.