Keeley (Ross) Compressor not working (CA3080 suspected)

[fakcior]

Hello,
recently I've built Keeley Compressor. It doesn't pass any signal. By checking it with audio probe I noticed signal on pins 2 and 3 on CA3080, but there's nothing coming from pin 6. All voltages are correct (like on Fuzz Central), except pin 5. There is only 0.01-0.15V depending on sustain knob. Hot (sustain pot's) side of 27k resistor varies from 0.5V to 8.2V. Q5 voltages are OK. Sustain pot is 500k.
Should I look for IC replacement or something else is causing the problem?
Regards

[PRR]

Where did you get your 3080?

[fakcior]

Banzai

[gritz]

In an ideal world pin 5 should be vaguely around 0V5 to 0V7 with current running into it. As the hot end of the 27k resistor is going up and down as expected then either the 27k resistor isn't 27k or the CA3080 is fubar, or maybe (just maybe) there's a partial short caused by a whisker of solder, or somesuch. Good luck! 

[fakcior]

Solved! It was faulty CA3080.

[jcmorse563]

im having some problems with mine as well, for some reason the unit acts like its gated.  if no signal is present, or if a i send a low amplitude signal in, (or if i pluck the guitar stings soft) if i pluck them harder or raise the amplitude on the generator the circuit works,  sort of...  other problems i have i used 100k pot instead of 150k shouldn't have made much differences, but what occurs is that in the top range of the attack it shuts down the circuit,  the last this is that the signal flows after i pluck the string hard, but after about 3 seconds volume cuts off by over 50% suddenly unless i pluck the string again. Didn't notice this with the generator as has constant signal. Any ideas where i should look?

[jcmorse563]

ok im having problems with this build...  for some reason when the sustain pot drops below 100k resistance the circuit starts gating.  i know that it has to be a bias problem but i cant seem to get it... heres my voltages maybe you can help. two sets one when signal goes through and the other when its gating,,( i have the sustain pot turned up all the way. ) and im building the one without the clip stat.  with resistors... looking at this ive seen a few things to check but after doing all this work im still posting...

ic (good)                                        (bad)
1 nc (160mv)                             same
2 9.3                                        9.1v
3 9.3                                        9.1v
4  0                                            .1mv
5 .5                                            .65v
6  3.4                                         .74v  (i see this but havent found why)
7 10.9                                      10.9v
8 nc                                          100mv

q1
c 8.62                                       8.8
b 2.73                                       2.6
e 2.41                                      2.22

q2
c 9.1                                      10.97
b 2.68                                        .7
e 2.41                                        .2

q3
c 9.1                                         9.5
b 39.2mv (nc)                            same
e 0                                           mv

q4 same as q3

q5
c 10.9                                  11.1
b 9.6                                    9.5
e 9.3                                    9

[R.G.]

2 9.3                                        9.1v
3 9.3                                        9.1v

Pins 2 and 3 should be nearly the middle of the power supply voltage. I suspect that the resistor supposed to be pulling them to ground is open, or a connection to it is open.

[jcmorse563]

an up date i tested the 3080, its good. i swaped out q2 with 3904.  same problem.  Q2 shuts off when sustain pot is in short.

[jcmorse563]

thanks Ill check that...

[jcmorse563]

solved.  I've been using old boss boxes and recycling the inputs, and pots.  turns out the pot that i was using for the clipping had a uncut trace directly to power.  better check those better... onward.. next build voodoo, sparkle drive... thanks for the help.