MXR Distortion + reissue no power;

Started by beedoola, January 13, 2023, 11:34:32 AM

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antonis

Quote from: beedoola on January 14, 2023, 05:29:12 PM
What should the voltages be on the IC pins?

On pin 6 & 2 about 4.5V.. On pin 3 a bit lower or much lower (dependent on your DMM particular impedance)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

bartimaeus

check the datasheet, and you'll see that pin 7 should be power and pin 4 should be ground

https://www.ti.com/lit/ds/symlink/lm741.pdf?ts=1673717440091&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM741

pin 7 is the first thing i'd check: is the IC even receiving power? if the LED won't turn on, i'm guessing not

Dormammu

Quote from: beedoola on January 14, 2023, 05:29:12 PM
I replaced the R9 with 10ohm. I had figured R8 was 4.7k so I used that. Nothing. What should the voltages be on the IC pins?
Have you installed a DPDT or are you supplying signal and power directly to the IC ?

GibsonGM

I'm sure I'm not telling anything new when I say that the input jack has to have something inserted into it for power to switch on to the IC etc...since it's used to switch the ground connection...
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beedoola

MXR replied to my email and gave me the values; R8 is 10ohm and R9 3.9k.

I got it working but it will die and not produce sound. Pin 7 gets 9v. Some of the other pins were lower than 4.5v. I'll check again later. Maybe the IC is compromised.

I ditched the DPDT and just hardwired the circuit to On.