Debugging: Pearl OC-07 Octaver Clone

[elenore19]

Here we go...
1. I got bypass and a signal through the board.The only problem is the controls don't work. They all do something, but I can't hear any octaves going on. The lower octaves don't really add lower octaves, but more of a muffled more bassy sound. (As if the tone pot on your guitar was turned down) The upper octave adds a trebly sort of sound to it, more sharp. But no upper octave.
The trim pot doesn't affect the upper octave at all either, so I'm sort of stumped as of right now. The normal volume knob seems to do its job. When it's off, there's no sound, and when I turn it up it gets louder.
2. Pearl OC-07 Octaver Clone
3. http://gaussmarkov.net/wordpress/circuits/octaver-clone/
4. No mods.
5. No Parts substitutions.
6. umm..no conversion..
7. I don't have a 9V battery available, so I just hooked up the power supply. The light comes on and what not, and I have voltages through the board...hopefully that won't be a problem...

Crunching the numbers:
I just have the voltages for the chips right now. I'll get the others if needed.
Just based on my ignorant observations, I'd say IC4 looks a little rough...

IC1
p1-5.02V
p2-5.02V
p3-4.54V
p4-0
p5-4.69V
p6-5.02V
p7-5.02V
p8-9.16V

IC2
p1-8.65V
p2-8.36V
p3-9.16V
p4-9.16V
p5-9.16V
p6-8.23V
p7-8.56V
p8-1.312V
p9-0
p10-7.07V
p11-10mV
p12-8.35V
p13-7.08V
p14-8.62V

IC3
p1-0
p2-0
p3-0
p4-8.62V
p5-0
p6-1.307V
p7-0
p8-0
p9-9.16V
p10-0
p11-9.16V
p12-9.15V
p13-0
p14-9.16V

IC4
p1-0
p2-9.16
p3-9.15V
p4-0
p5-0
p6-0
p7-0
p8-0
p9-0
p10-0
p11-0
p12-0
p13-9.16V
p14-9.16V

IC5
p1-4.94V
p2-4.95V
p3-4.94V
p4-9.16V
p5-4.66V
p6-5.0V
p7-5.0V
p8-5.02V
p9-5.02V
p10-5.01V
p11-0
p12-4.74V
p13-5.02V
p14-5.02V

IC6
p1-5.02V
p2-5.01V
p3-5.01V
p4-9.16V
p5-5.02V
p6-5.02V
p7-5.02V
p8-5.81V
p9-5.01V
p10-5.01V
p11-0
p12-5.01V
p13-5.01V
p14-4.90V

Thanks for the help!

Let me know if you have any questions or need any other measurements.

-Elliot

[PRR]

> I'd say IC4 looks a little rough...

Nah, IC4 digital, everything should be zero or B+. Flip-flipping while you play, but too fast to prove with a simple meter.

> The normal volume knob seems to do its job. When it's off, there's no sound

No, the circuit generates FOUR signals: Normal, Upper, 1-Down, 2-Down. With Normal full-down, you should hear the other outputs.

That said.... this is an enormously complex circuit (for a pedal) and may not be a trivial debug. I might start with a signal-tracer, listen to various points in the circuit while playing (a fake-guitar would be handy; feed signal while you poke the signal tracer.)

Output of IC1B should be very mellow clean signal.

All outputs of IC2 should be very-buzzed-up signal.

All "Q\" outputs of IC3AB and IC4A should be even more buzzed-up signal.

Disconnect any leg of Q2 and Q3. Now the 1-Down and 2-Down outputs should be normal clean but super-mellow.

[elenore19]

> I'd say IC4 looks a little rough...

Nah, IC4 digital, everything should be zero or B+. Flip-flipping while you play, but too fast to prove with a simple meter.

> The normal volume knob seems to do its job. When it's off, there's no sound

No, the circuit generates FOUR signals: Normal, Upper, 1-Down, 2-Down. With Normal full-down, you should hear the other outputs.

That said.... this is an enormously complex circuit (for a pedal) and may not be a trivial debug. I might start with a signal-tracer, listen to various points in the circuit while playing (a fake-guitar would be handy; feed signal while you poke the signal tracer.)

Output of IC1B should be very mellow clean signal.

All outputs of IC2 should be very-buzzed-up signal.

All "Q\" outputs of IC3AB and IC4A should be even more buzzed-up signal.

Disconnect any leg of Q2 and Q3. Now the 1-Down and 2-Down outputs should be normal clean but super-mellow.

Is there any way of me figuring out the problem without having a signal tracer? I don't have one.
Good to know on the four circuits thing. I'll check and make sure that I said the right thing as to what the volume knob does does.
Thanks for the reply! Appreciate the help. I think I'm in over my head here.

[zeta55]

How does it sound compared to the soundclips from my site?
http://www.zeta-sound.se/effects_eng.html
Scroll down a bit.

/Krister

[PRR]

> a signal tracer? I don't have one.

You have the parts. Build it!



Use the small cheap amp, not something very-fine. Keep the amp gain/volume set "mild", like playing at home. The signal-tracer volume control should be handy at the bench, because you will turn-up for weak signals and TURN DOWN NOW! when you hit a strong signal.

Cap voltage suitable for the bigest voltages you will ever use it with. For today, a 10V cap is enough. A 50V cap will be good for most solid-state stuff.

Around ICs, those push-claw probes may be better than the alligator clips I drew. I don't like meter-probes or nails for this use, they slip which leads to loud sounds.

[stringsthings]

thanks for this signal tracer diagram .... tracers make troubleshooting more fun ...

... Use the small cheap amp, not something very-fine ...

+1

DIY tip #789:    a battery-powered mini-amp makes a good testbench amplifier .... you can sometimes find them packaged with sets of guitar strings