4:1 compressor problem

[Dawnofzion]

I finished up a 4:1 compressor build and have ran into some problems. With the effect on, it does nothing....there's no compression.  I get sound but no compression.  I just went through and checked all values of parts and everything is correct.  I also reflowed all solder joints. Still getting the same thing.  The compression pot does nothing.  The clean pot works to raise and lower the volume.  With the clean knob down to 0, there is no signal. The comp knob or the sustain knob do nothing.  Any ideas?  Could my opto be cooked?  Picture of board below.




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[Dawnofzion]

Any suggestions?


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[m-Kresol]

Please post voltages of all ICs. Also I would recommemd to audioprobe the compression circuit: C4, IC2 pin 5, 6 and 7, the compression pot and so forth

[Dawnofzion]

 Ok I finally got around to measuring all the voltages of this pedal.  They are shown below.  I found it odd that I had no voltages at the compression pot. I turned it to see if that mattered and it didn't.  Any ideas?

[m-Kresol]

well, there clearly is a problem around IC2. You've got no voltage or way too low on pins 1, 2 and 7. You've got what lloks like a 51k for R12 instead of 47k, but I doubt that that is the reason. I think the culprit is most likely somewhere between Pin 7 and 2. pin 5 and 6 are ok, so 7 should be too unless something pulls down the voltage there. The low voltage on pin 2 would cause the voltage on pin 1 to go bananas.

the compression pot is ok not to show voltage, the capacitor blocks any DC voltage, so there should only be AC.

I would do the following:
*) recheck all components and look for solder bridges
*) reflow the area around IC2.

I have no experience with this sort of vactrol, but assuming the dot is the anode you've put it in correctly. The voltages are in agreement with the pins of IC2 it's attached to.

sorry I couldn't be of more help. hope you get it working

[Dawnofzion]

Should I try replacing IC2?
I went through and checked the resistors and caps and all seem to be correct other than the one you mentioned.

[Dawnofzion]

Still can't figure this one out. I haven't replaced ic2 or the opto yet.  I'm wondering if that should be my next step?


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[m-Kresol]

it is possible you fried the IC since you soldered it in directly. However, half of it seems to be working (pin 5/6).
if you decide to desolder I would advise to carefully cut the legs of the IC and desolder them individually. lowers the chance of lifting pads.

Sorry I can't be of more help, I don't see anything wrong on the pics.