1

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

« on: February 22, 2026, 10:09:45 AM »

Check if you get the signal on U1 pin 5.
- If not, the issue is around the high pass filter. Check the solder joints on rotary switch SW1, connectors J5a-b and J6a-b.
- If true, the issue is in the relay RLY1 or in U2. Check the solder joints. Try replacing.

2

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

« on: February 20, 2026, 11:36:28 AM »

Also check TP3 and TP4 (the audio goes through them before TP2).

3

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

« on: February 18, 2026, 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.

4

AB528 Microphone preamplifier / Re: AB528 DI not working

« 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.

5

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

« 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

« 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.

7

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

« 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.

8

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

« 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.

9

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

« 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) ?

10

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

« 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.

11

AB528 Microphone preamplifier / Re: AB528 DI not working

« on: February 06, 2026, 10:41:04 AM »

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

12

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

« on: February 04, 2026, 06:49:49 PM »

It is just in parallel with the input, without buffering.

13

MC624 Monitor Controller / Re: 12 year old manual recommendations outdated

« on: February 04, 2026, 08:57:06 AM »

Hi,
We use this one.
We couldn't find a TV model that worked 100% so we programmed the MC624 manually for this remote.

14

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

« on: February 04, 2026, 08:46:32 AM »

Check that the input potentiometer is working by measuring the resistance between pins 7 & 10 of the input transformer. The value should vary from 0 to 200 ohms when rotating the input potentiometer.

15

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

« on: January 30, 2026, 04:25:52 PM »

It looks like a sidechain gain issue.
Check the solder joints of R22, R23, R28, D4.

16

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

« on: January 28, 2026, 03:37:12 PM »

When this happens, does the needle return to 0 if you remove the signal completely?

17

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

« on: January 26, 2026, 09:40:55 AM »

I am not sure I understand well.
Do you have a sudden excess of input gain? Does it looks like a bad contact? How does it ends? Please explain more.

18

CP5176 FET compressor / Re: No sound CP5176

« on: January 26, 2026, 09:32:16 AM »

That looks very much like your issue.
One of the phase is not connected.
It can also explain the low levels.

19

CP5176 FET compressor / Re: No sound CP5176

« on: January 23, 2026, 05:10:16 PM »

I am running short of ideas. 
Do you want to send it to us for a check? Contact me at jpk@soundskulptor.com

20

CP5176 FET compressor / Re: No sound CP5176

« on: January 23, 2026, 09:47:41 AM »

The values are correct.
Check that the input transformer is inserted the right way around, with the markings facing upwards.
Check that the relay is inserted the right way around, with the white line down.
Check that the resistance between TP1 and ground goes from 0 to 1k6 when turning P1.

21

CP5176 FET compressor / Re: No sound CP5176

« on: January 22, 2026, 03:20:25 PM »

I suppose that you mean the fingers on CN3a?
No. I mean the card edge connector at the back of the card with golden fingers (connecting to the lunchbox).

And without any power I suppose?
Correct

22

EQ250 stereo equalizer / Re: EQ 250 setup question

« on: January 22, 2026, 11:55:24 AM »

Yes correct.

23

CP5176 FET compressor / Re: No sound CP5176

« on: January 22, 2026, 11:54:08 AM »

With the P1 set max I can also read 0.11 VAC on TP1
Does this voltage vary, from 0 to max) with the P1 rotation?

Check the input transformer coils resistance:
Between edge connector fingers 8 & 10 (counting down, including absent fingers): 2k
Between side pins of P1: 1k6

But the signal is lacking all bass
Are you sure you are connecting the output with a balanced cable? This lack of bass happens when only one phase is connected.

24

Discussions about the products / MOVED: EQ 250 setup question

« on: January 21, 2026, 06:16:01 PM »

This topic has been moved to EQ250 stereo equalizer.

https://www.soundskulptor.com/forum/index.php?topic=7394.0

25

EQ250 stereo equalizer / Re: EQ 250 setup question

« on: January 21, 2026, 06:13:13 PM »

You can use a plugin in your DAW that generates a variable frequency sine wave (there are several free plugins available like tonegenerator) and adjust the frequency for the maximum output signal.