1

AB528 Microphone preamplifier / Re: AB528 DI not working

« Last post by Ritualknive on February 13, 2026, 10:47:50 PM »

1. -15.34
2. -15.72
3. -16
4. -16

5. -14.4 but can here relay switch then 3.77
6. -14.4
7. -13.6
8. 15.8

That’s with nothing plugged into DI

2

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?

3

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.

4

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.

5

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) ?

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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!