1

EQ573 Equaliser / Re: EQ573-II doesn't play sound

« Last post by JPK on Today at 04:48:29 PM »

Check the value and solder joints of R1...R4, C4, C5, U1, RLY1.
Check the direction of U1, RLY1.
Try swapping U1 with one that you are sure of.

2

EQ573 Equaliser / Re: EQ573-II doesn't play sound

« Last post by andrixb on Today at 11:45:53 AM »

Hi

Thanks for the suggestion.

I get a sound in bypass if it is connected to the MP573; nothing gets through otherwise.
On TP1, I get 0VAC. The board is REV2.3B, and the C8 is oriented as in the picture (negative facing the back of the launchbox)

3

AB528 Microphone preamplifier / Re: AB528 DI not working

« Last post by JPK on February 17, 2026, 10:18:48 AM »

Not good! Pins 1, 2, 3, 6 shoulb be at 0V.
Check the solder joints on J4a-J4b.
Look for a solder bridge on U2, on the jack or on the connectors J4a-J4b.


Maybe one of them is no good?
You can check them in circuit with your DMM in diode test mode.

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AB528 Microphone preamplifier / Re: AB528 DI not working

« Last post by Ritualknive on February 16, 2026, 09:37:01 PM »

They are in correctly. Maybe one of them is no good? Also I’m also now noticing when using the mic/line in the 1200 ohm position there is a constant tapping or ticking type of sound. Only on the 1200 setting. 

5

EQ573 Equaliser / Re: EQ573-II doesn't play sound

« Last post by JPK on February 16, 2026, 05:32:44 PM »

Do you get a sound in bypass?
You must try to follow the signal on TP1, TP3, TP4, TP2, as described here.
It will tell you where the signal stops.

6

AB528 Microphone preamplifier / Re: AB528 DI not working

« Last post by JPK on February 16, 2026, 05:22:32 PM »

Check that diodes D12 and D13 are installed in the correct orientation: The "k" on the PCB is the ring on the diode.

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EQ573 Equaliser / EQ573-II doesn't play sound

« Last post by andrixb on February 15, 2026, 02:40:08 PM »

I would need help with this module, please.
The module doesn't play any sound when in both pre and XLR mode.

V values match what is reported here: https://www.soundskulptor.com/forum/index.php?topic=25.0

I checked the tension, and I measured 16V.
Also,  I followed this thread too and around diod D2 I measure -15V / 7V (it goes 7V / -15V when I select XLR) https://www.soundskulptor.com/forum/index.php?topic=362.0
I checked all the solder joints around what is suggested, but the value around D2 measured doesn't change at all.

Thank you

8

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

« Last post by JPK on February 14, 2026, 04:21:51 PM »

We get them from OMEG.
Model: LT16BU - 100KB - BUSH C/6MM
Contact me if you can't find one.

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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

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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?