1

MU524 Vari-Mu Tube Compressor / Re: Low output voltage step 6

« on: April 07, 2026, 09:04:14 AM »

Can you please also report the values on TP2 and TP3?

2

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« on: April 01, 2026, 05:46:35 PM »

Check the solder joint on D20.
If solder joints are OK try to replace D20 (Zener 4V7-1.3W).

3

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« on: March 30, 2026, 11:19:39 AM »

The diodes D10, D11 on the front PCB have no effect on the the output stage bias setting.
Is the voltage on TP3, against 0V stable, around -11.5V ?
Is the bias voltage bouncing when you tap the PCB or specific components with a pen ?

4

MU524 Vari-Mu Tube Compressor / Re: Low output voltage step 6

« on: March 27, 2026, 04:08:55 PM »

Remove U4.
What values (DC and AC) do you get on TP1 to TP4 in the initial conditions here.

5

CP5176 FET compressor / Re: My CP 5176 is very quiet on the input stage

« on: March 27, 2026, 04:01:52 PM »

D -1.35VDC
Something wrong here.
Check Q4 (BC550C), R11 to R15.

6

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« on: March 24, 2026, 05:03:39 PM »

No problem, these diodes are very close.

7

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« on: March 21, 2026, 09:48:02 AM »

You could look for a continuity between ground and C8, C9, C10. But the best thing to do will be to shorten the pins.

8

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« on: March 18, 2026, 12:14:19 PM »

I only get resistance from 0.3ohms to about 1.6Kohms
Normal because the trimmer is in parallel with R31+R32.

I have added some DC voltage checks to do here. Please compare with your values.

9

CP5176 FET compressor / Re: My CP 5176 is very quiet on the input stage

« on: March 17, 2026, 05:33:08 PM »

I changed Q1 but that was not the issue
Did the sound return when Q1 was disconnected?

I see that R56 and R57 changed color a little.
This means you have a short circuit somewhere. Are they getting hot? 

A little burned the resistance is correct and they are just for power right? But that cannot be an issue?
You can check their value with your ohmmeter (in circuit).

Do you think it might be transistor or capacitor?
Not a capacitor. Neither a transistor if you got the DC voltages right in the picture here.

10

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« on: March 17, 2026, 05:23:21 PM »

I moved on and could not get past step 6
What happened at step 6?

Check the solder joints on R26, Tr2, R31.
Check the wire connections to the transformer, look for a thread that might be causing a short circuit.

I was checking for shorts anywhere and did find continuity between two pins on U3
Pins 1 and 2 are connected by a 7R5 resistor, whick way look like a short.

11

MP573 Microphone preamplifier / Re: Inline-attenuator after MP573 and before interface

« on: March 15, 2026, 09:56:49 AM »

It should work. Just check in the specs that they can handle the high line level.

12

TS500 Tape Simulator / Re: “bump” problem

« on: March 05, 2026, 04:57:16 PM »

I noticed a bump when I switch to 30ips from 15ips, and from 7.5 to 15ips.
Do you also get these pops when there is no input signal?
You can compare to the other unit when it is finished.

I have one 100pF to insert in c65.
Sorry for the mistake. Yes, a 100pF will be OK.

13

CP554 Diode bridge compressor / Re: V+ and V- voltage

« on: March 05, 2026, 04:40:02 PM »

Not an issue. The Wes is just a little above the standard voltage.

14

CP5176 FET compressor / Re: My CP 5176 is very quiet on the input stage

« on: March 05, 2026, 03:55:57 PM »

Try removing Q1 on the broken unit. If the sound is back then Q1 is the culprit.

15

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.

16

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).

17

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.

18

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.

19

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.

20

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.

21

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.

22

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.

23

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) ?

24

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.

25

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?