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MU524 Vari-Mu Tube Compressor / Re: Initial AC voltage jump

« on: January 26, 2026, 04:50:50 PM »

So in that photo I have a vocal running through and if you look at the knobs, all of them are down. But the signal is still getting slammed. I can faintly hear the source even with the output down. The signal is distorted as well. But again, this is not a constant issue. Sometimes it slams the signal, and sometimes it operates normally.

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MU524 Vari-Mu Tube Compressor / Re: Initial AC voltage jump

« on: January 24, 2026, 11:19:45 PM »

Here is a shot

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MU524 Vari-Mu Tube Compressor / Re: Initial AC voltage jump

« on: January 24, 2026, 07:08:51 PM »

I wanted to jump back on this thread real quick and ask about another jump. This same unit will jump up in input after using it for several minutes. The meter will peg right and distort. So when it does this I can turn the input and output all the way down and still faintly hear it. But then last night I used it for a couple of hours and it never had an issue. 🤷🏼 I swapped slots on the rack to double check as well

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MU524 Vari-Mu Tube Compressor / Re: Initial AC voltage jump

« on: January 05, 2026, 06:27:18 PM »

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

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MU524 Vari-Mu Tube Compressor / Re: Initial AC voltage jump

« on: January 03, 2026, 04:29:42 PM »

for reference

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MU524 Vari-Mu Tube Compressor / Re: Initial AC voltage jump

« on: January 03, 2026, 03:47:31 PM »

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

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MU524 Vari-Mu Tube Compressor / Initial AC voltage jump

« on: December 27, 2025, 04:43:53 PM »

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. 

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MU524 Vari-Mu Tube Compressor / Re: My Problems begin at step 6 of setup

« on: October 24, 2023, 11:30:51 PM »

After removing C12 and replacing it, I still get the same results. I did want to mention though, that once I dial in my 1k tone at 1.0VAC, and I switch the compressor on, it does increase the voltage slightly. Instead of a 3-4v increase, I get a .003-.004v increase. Since it's off by 1000, do I have a component value off somewhere?

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MU524 Vari-Mu Tube Compressor / Re: My Problems begin at step 6 of setup

« on: October 22, 2023, 05:26:05 AM »

Ok, I ran the tests you mentioned, and also double checked the transformer direction. The transformer was good, and I did not get any change in voltage after removing U4, and did not show any voltage across T3 and T4. That was with the front panel removed. I went ahead and ordered another C12 because I do have a pin that is very close to the capacitor. I believe the pin touches the capacitor so there's a good chance it could be damaged.

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MU524 Vari-Mu Tube Compressor / My Problems begin at step 6 of setup

« on: October 18, 2023, 02:40:19 PM »

Ok I'll try to keep it short, but I do want to include some other findings. I went through the troubleshooting guide before I posted just so some of the questions don't get redundant. But like the title says, my problems begin at step six. When I turn the unit on, I don't get the jump to 3-4v. It stays at 1v. I did go ahead and move forward, just to see what other numbers I got. I was able to get most of the voltages throughout the setup guide. If I remember correctly (it got late and my memory is foggy) I got to step 10 and was unable to get to the 3.6v. I ran out of turns on the TR4. I think one more voltage was off but I can't remember at the moment. Anyway, I got all the way to the end, and the input and output sections work just fine. I get gain up and down from both knobs, just no compression when turning up the input section, only gain. Where should I begin to look?


Edit:

Here are my test numbers

TP1 = TP2 41 VDC
TP1 = TP2 UNSTABLE
TP3 = TP4 0.51 VAC
OUTPUT = 1.032

TP3 0.23 VAC
TP4 2.86 VAC
TP5 2.61 VAC
TP6 -3.1VDC
METER -6db