Twin Peaks Tremolo troubleshooting help please

[AntKnee]

I could be crazy, but I'm starting to think my problem might be the test rig. I will take steps to rule that out tomorrow.

On my test rig, if I crank up the test tone volume and the headphone volume, I can barely hear proper effected signal.

[AntKnee]

I could be crazy, but I'm starting to think my problem might be the test rig. I will take steps to rule that out tomorrow.

On my test rig, if I crank up the test tone volume and the headphone volume, I can barely hear proper effected signal.

Its not the test rig.

Am I correct that if the octos are working properly, I should hear audio with a probe at C6 and C7?

[AntKnee]

With C6 and C7 removed, I hear clear loud audio input and faint effected audio output at the optocouplers. I hear faint effected signal on the + pads of C6 and C7. If I insert C6 and C7, the audio dies. I am using non bipolar electrolytic capacitors. Are they the problem?

Here are the caps I used:
http://www.mouser.com/Search/ProductDetail.aspx?R=ECE-A1EN100Uvirtualkey66720000virtualkey667-ECE-A1EN100U

[drolo]

so you mean, going into the optocouplers, you have a clear loud signal, but at the output pad of the optocouplers not?
For both of them?
If yes then there still seems to be something wrong around ldr's

[midwayfair]

so you mean, going into the optocouplers, you have a clear loud signal, but at the output pad of the optocouplers not?
For both of them?
If yes then there still seems to be something wrong around ldr's

Isnt one side of the optocouplers the inverting input of an opamp? On mobile so going by memory here, but you wouldn't hear any audio there, you'd have to check the output pin of the opamp.

[AntKnee]

Then I suppose what is happening with my capacitors at C6 and C7 is fine.
Which pin would that be? (schematic posted earlier)

[AntKnee]

I have dry signal at pins 5, 6, 7, 8, and 14
Edit: C6 and C7 are reinstalled

[drolo]

so you mean, going into the optocouplers, you have a clear loud signal, but at the output pad of the optocouplers not?
For both of them?
If yes then there still seems to be something wrong around ldr's

Isnt one side of the optocouplers the inverting input of an opamp? On mobile so going by memory here, but you wouldn't hear any audio there, you'd have to check the output pin of the opamp.

Actually the 2 signals are now decoupled with caps. (I was having some ticking issues with very low on resistance of certain LDR's) So it's still a mystery that there is sound at one end of the LDR's and not at the other if the resistance drops according to the LFO. Could you post high resolution pics of both sides of the PCB ? perhaps we'll be able to spot something.

[AntKnee]

[AntKnee]

What if the LED side isn't getting enough power? Since I have very faint audio at the effect output, maybe it is working correctly, but the octocoupler isn't getting bright enough?

[drolo]

What if the LED side isn't getting enough power? Since I have very faint audio at the effect output, maybe it is working correctly, but the octocoupler isn't getting bright enough?

Let's try the following:
Set your depth knob to minimum.
Measure your LDR resistances.

[AntKnee]

I'm measuring about 28m on both, but it increases/decreases slowly.

[drolo]

I'm measuring about 28m on both, but it increases/decreases slowly.

like 28 megaohm ?

[AntKnee]

like 28 megaohm ?

Yes, that is what my meter is reading. If I change the range to ohms or kilo ohms, it only reads "OL".
Also, this is with C6 and C7 reinstalled, so I'm not sure if I'm getting a realistic resistance reading with the circuit operating.

[drolo]

Right now it looks like the resistance is not getting low enough to let any signal through
at half depth it should be low enough to let significant signal through.

Could you measure what voltage change you are getting at pin 5 of the taplfo (with depth full and square wave) should be between 0 - 5 v
Same for pin 1 and 7 of the LM358. swing should be 5v peak to peak centered around your 3.3 v reference

If you are getting these voltages, would you feel comfortable desoldering the LDR side of the vactrols to measure the resistance with them out of the circuit (leaving the LED side connected)?