Author Topic: Initial AC voltage jump

December 27, 2025, 04:43:53 PM
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CGMix

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After sending a 1V, 1K tone of not the compressor, my voltage jumps to a little over 7V instead of 3-4V. This does affect the rest of the calibration. Where should I look? All other voltages look to be where they should. 

December 31, 2025, 09:35:25 AM
Reply #1

JPK

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Check that you have not reversed transformer T1. The label must be facing the back of the module.
What are the AC levels on TP3 and TP4, relative to 0V (1.75V)?
JPK

January 03, 2026, 03:47:31 PM
Reply #2

CGMix

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JP! Thanks for the reply. At TP3/4 I’m getting 3.9vac. On my other working compressor it sits at 1.8, I believe. I pulled the transformer last night, thinking I may have pierced R1, but I had not. Also, I’ll have to check again, but I think I was measuring about half a volt on each grid of the tube. And then it jumps up to about the 4V pretty quickly thereafter. I believe the Transformers is correct because it’s installed in the same manner as my other

January 03, 2026, 04:29:42 PM
Reply #3

CGMix

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January 05, 2026, 10:06:16 AM
Reply #4

JPK

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Is the label on the transformer facing towards the back of the module?
Check the input transformer coils resistance (in circuit with potentiometer IN on 10):
pin2-pin4 : 37ohms
pin3-pin5 : 37ohms
pin7-pin9 : 98ohms
pin8-pin10: 98ohms
pin7-pin10: 194ohms





JPK

January 05, 2026, 06:27:18 PM
Reply #5

CGMix

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Well damn, that was it. Transformer was upside down…

January 06, 2026, 04:11:47 PM
Reply #6

JPK

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