Ibanez CP 830 not working

[Ghost Planet]

A guy from my church gave a script logo Ibanez CP 830. He said it was laying around in his garage. When I opened it the battery was a brick of rust. I took it apart and cleaned all the jacks and battery snap, but it does not work. It will pass bypassed signal, the pots are good, and the circuit is receiving current. When I touch on the board on the tracks I do get buzzing. An ideas on what could be wrong? Thanks.

[mth5044]

Check out the debugging page stickies at the top of this forum.

Two things that are always good places to start is to check coltages on all active components (IC's, transistors, etc), and use a signal probe to find out where you signal is stopping.

[Ghost Planet]

All the transistors and IC are receiving voltage. Could it be the optocoupler?

[mth5044]

Receiving voltage is not the same as recieving the correct voltage. It could be the optocoupler, it could be anything! Check out the debugging page. Use a signal probe to find out where your signal is stopping. We could speculate all day, randomly, but with some data, tracking down the problem becomes easier.

[Ghost Planet]

I will try the probe, thanks.

[Govmnt_Lacky]

Some good pics of a block logo unit here. Should be just about identical to what you have:

http://www.tonehome.de/ibanez-effects/narrow-box-series-w-round-switch/cp-830-compressor/

EDIT: Link also has a factory schematic. IF it is a bad optocoupler, the original specs were 150 ohm on/1M off

[Ghost Planet]

Thank you so much for the pics and the schematic. Im going to probe the circuit soon, the schematic will be a great help.

[Tony Forestiere]

Thanks for the link, Greg. Looks like a very low parts count.

[Rob Strand]

It should be easy to get working.

The schematic is good.  Some units have the detector circuit TR1, TR2, TR3 connected to the Vcc/2 point (ie. C16 + terminal).  I've seen VR1 = 560R *resistor* not 22k.

To me, the problem is around the opamp/amplifier not the detector.

The first thing to check is the DC voltages at the Vcc/2 point and at the output of the opamp.
You might have faulty electrolytic caps in one of the positions C16, C2, C1 or elsewhere

Even if the LDR was short for some reason it should at least pass a clean signal; all be it a little low in level.  If you lift the resistor R14  the unit should function as a booster and the sustain pot will control the gain.