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

« Last post by CGMix on February 13, 2026, 05:24:52 PM »

OK I tested all three pots while I had the front panel pulled, the bottom two were in range and the input potentiometer just showed out of limit. But I believe it might have a break internally. If I wiggle the stem, it will jump in ohms. do you know where I can get another one of these in the US?

22

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

« Last post by JPK on February 13, 2026, 04:15:02 PM »

It’s stuck at 100ohms
Check the input pot directly on its pins, with the front PCB disconnected.
It should go from 0 to 10kohms.

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

« Last post by CGMix on February 13, 2026, 12:56:40 AM »

OK I checked all of those connections again and I still have the same results. However, I  have a second unit that I pulled the front panel off of and swapped them around. so taking the front panel with a known issue and putting it on a compressor with no known issues, it still behaves in the same way. So I believe the issue is within the front panel. Have you ever come across a bad potentiometer? I think I may pull it out and measure it.

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DI503J Triple DI and Re-Amp / Re: Broken pads on potentiometer board

« Last post by JPK on February 12, 2026, 02:59:45 PM »

It is possible to repair by soldering a wire between the pot pin and the circuit.
Which pad of which pot is damaged (or show a picture) ?

25

DI503J Triple DI and Re-Amp / Broken pads on potentiometer board

« Last post by slynch on February 10, 2026, 05:39:49 PM »

Well this one really hasn't gone well for me. I think I went too fast and I ended up having a few major mistakes in my build. I thought I had eventually figured it all out and fixed the issues but...

One of the major issues was that I accidentally switched the potentiometers P1 and P2. When I realized this, I removed them and installed them in their correct location, but I damaged the board in the process. I confirmed that at least one pads under the pot was lifted or damaged.

So what's the process to get this fixed now if the board is bad?

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

« Last post by JPK on February 09, 2026, 03:55:00 PM »

Check the solder joints of the potentiometer P1, of the connectors J2a and J2b and of the transformer daughterboard to main PCB connector.

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

« Last post by CGMix on February 07, 2026, 06:51:39 PM »

Yeah it looks like that may be it. The ohm load doesn’t change. It’s stuck at 100ohms

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AB528 Microphone preamplifier / Re: AB528 DI not working

« Last post by JPK on February 06, 2026, 10:41:04 AM »

Can you report the DC voltages on each pin of U2 on the DI board?

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AB528 Microphone preamplifier / AB528 DI not working

« Last post by Ritualknive on February 06, 2026, 02:17:46 AM »

Just put together one of these. Mic and line work well along with the phantom power. DI all I hear is hiss and the front LED doesn’t work either. Any ideas? Thanks! 

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DI503J Triple DI and Re-Amp / Re: DI503J triple DI output buffer

« Last post by TheWoodman on February 04, 2026, 06:55:54 PM »

Thanks very much for your answer. Depending on levels/impedance this possibly thins out the instrument signal a little when another load (amp for example) is connected to the unbuffered TS output. Which can easilly be handled by placing my own buffer before the input. So thanks again, this is just good to know.