Build Your Own Clone Message Board

Hello, I built the peq a month or so back and it was working perfectly. A few days ago I turn it on and there was no signal coming through at all. In bypass the signal comes through but nothing when on. I found the post about the error on rev. 1.0 boards and corrected that and now I get a buzz/hum and no guitar signal when pedal is on and a guitar signal with a buzz when in bypass.

I am stumped about what caused the original problem to suddenly appear after a month of flawless use. I am not using a power supply with it and I have tried several new 9v batteries. Any ideas?

Thank you

Okay so I tried insulating the pots from the board, and I've been trying to take voltage readings on the op amps. I ha e the pin-outs but I'm not sure what values I should be getting. I used a probe and have narrowed it down to only giving me a buzz when I pick up the audio from the "high" quad op amp. I replaced all the op amps with similar types and I get no sound at all when pedal is on. Does anyone see something or have an idea where else I should look?

For the 3 TL074's, you should have about 9 volts on pin 4, -9 volts on pin 11, and about zero volts on all the other pins. For the dual opamp, +9v on pin 8, -9v on pin 4, 0 volts on the others. those voltages will tell us if the max chip is working - no need to measure voltages there.


What type of probe are you using?

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

The probe is the test probe sold at byoc with the audio jack.

I tested the voltage at pin 4 on the three quad op amps and get 5V. On pin 11 I get 0.7 so looks like I should try changing out the max1044?

Remove the 1044 and remeasure those voltages. You should get about 9 volts on pin 4 and nothing on pin 11. That would indicate the 1044 is dead. If that's the case, be careful with your supply voltage. Some unregulated "9 volt" wall warts are put out upwards of 12 volts, which can fry a 1044. You need to be careful to not feed the pedal more than 9 volts.

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

I put a new battery in so I would be getting a full 9v and took out the 1044. It was like you said, 9v at pin 4 and nothing at 11. I'll have to check the output voltages on my power supplies to find out which one was the pos. thanks for the help. I'll replace the 1044.

I started using a different power supply that measures exactly 9v and have burned up another 1044 chip. Is there a problem somewhere else that could cause the 1044 to continue to fail or would moving down to a 7.5v power supply solve the problem and still be able to fully power the circuit? I love the EQ but don't want to replace the 1044 every two times I use it.
Thanks