1

DI503J Triple DI and Re-Amp / Re: Extremely low output

« on: May 13, 2024, 06:13:10 PM »

You can try to send a strong test signal (sine 1VAC) at the instrument input and check you can measure it

- on TP1 (against 0V) at the same value,
- between pins 2 & 3 of U3, attenuated to 80mVAC,
- on TP3 (against 0V) after preamp, level depending on preamp gain.

2

DI503J Triple DI and Re-Amp / Re: Extremely low output

« on: May 11, 2024, 05:57:07 PM »

So the preamp is working, right?
Maybe a bad solder joint :
Check the resistor R1, transformer T1, switch SW5, relay RLY4.

3

DI503J Triple DI and Re-Amp / Re: Extremely low output

« on: May 10, 2024, 09:29:51 AM »

Does the gain drop occur in all 3 modes?
Is there a difference in level when you turn on the preamp?

4

MP573 Microphone preamplifier / Re: MP573 unstable, volume drop

« on: May 06, 2024, 05:39:07 PM »

This sounds like a weak solder joint. I would first check things around the power transistor because the changes in time could be caused by the device getting warm.

5

CP4500 Stereo Bus Compressor / Re: CP4500 meter intermittently unresponsive

« on: May 06, 2024, 05:34:35 PM »

First, I would check the connections between the meter and the PCB, in particular the female connector on the PCB side.

6

CP4500 Stereo Bus Compressor / Re: Compression happening randomly

« on: April 29, 2024, 11:58:47 AM »

7

MU524 Vari-Mu Tube Compressor / Re: Cant find problem in my build

« on: April 29, 2024, 11:58:07 AM »

Your values on TP4 and output are good. The error was mine and I have corrected the values in this page. I am sorry for the confusion.
The noise in the output shown in your video comes from bad balance settings on trimmers TR1 and TR2.

8

MU524 Vari-Mu Tube Compressor / Re: Cant find problem in my build

« on: April 26, 2024, 04:27:09 PM »

The unrealistic output level of 22.67VAC could be caused by the DMM.
What says the dB meter in the changed conditions. It should show -6dB.
Have you tried to listen to the output. How does it sounds?

9

MU524 Vari-Mu Tube Compressor / Re: Cant find problem in my build

« on: April 23, 2024, 06:05:49 PM »

Your values look better.
It is only  the output AC volatge that seems a little high.
Are you sure about the input voltage of  1VAC? It should be measured with the compressor connected.
Check the total resistor value of P2, between the 2 side pins (remove U1 and U2 for this measurement).
Check the value of R16.

10

MU524 Vari-Mu Tube Compressor / Re: Cant find problem in my build

« on: April 22, 2024, 09:56:30 AM »

TP1 to 0V = 67.3VAC
TP2 to 0V = 67.3VAC
This is just not possible. I am afraid your meter has a problem. Can you find another meter?

11

MP573 Microphone preamplifier / Re: MP573 low signal level

« on: April 21, 2024, 09:36:02 AM »

also for the signal trace test i set the volume to reach 0,88vac at input transformer pin 7
This doen't allow you to eliminate a possible failure in the input transformer. You must measure the signal at the input XLR between pins 2&3.

output transformer yel: multimeter cant properly read the value and changes between 114v, 0v, 7,4v and 14v
This looks like a disconnected wire. Can you check the wiring of the output transformer, the solder joints on the connector CN2 and the phase switch?

Measure the DC resistance at the output between hot and cold (make sure the phase in not on center pos).

12

MP573 Microphone preamplifier / Re: MP573 low signal level

« on: April 19, 2024, 06:15:16 PM »

The damaged pad is the cold input. It appears that a lot of current passed through this contact which should not happen.
You must look for short circuits. Did you cut all the pins of the headers on the daughter PCB of the input transformer short (under the input transformer)?
Did you connect a device to the input which could have some DC volts on its outputs ?
I have restored the diagram with the voltages on the forum.

13

MU524 Vari-Mu Tube Compressor / Re: Cant find problem in my build

« on: April 19, 2024, 05:50:47 PM »

In the initial conditions, you didn't give the VAC values of TP1, TP2, TP3, TP4 against 0V.
Are you sure that you meter is OK (battery checked)?

14

MU524 Vari-Mu Tube Compressor / Re: Mono / ST.L vs. ST.R

« on: April 19, 2024, 05:31:58 PM »

The left and right compressors are identical except for the tube heater supply where we use voltage regulators working at 2 far away frequencies in order to avoid the risk of noise caused by low frequency beat between these frequencies.

15

CP554 Diode bridge compressor / Re: Can’t get 3v in step 5 in setup

« on: April 10, 2024, 08:58:54 AM »

Can't wait!

16

CP554 Diode bridge compressor / Re: Can’t get 3v in step 5 in setup

« on: April 09, 2024, 06:59:27 PM »

Is this the correct Mouser part?
Yes, correct.

Would it be okay to replace it with a 3W?
Yes, no problem.

17

CP5176 FET compressor / Re: GR Meter not lighting up, D8 and D16 LED shows a short between pads

« on: April 08, 2024, 12:19:34 PM »

18

CP554 Diode bridge compressor / Re: Can’t get 3v in step 5 in setup

« on: April 08, 2024, 12:17:42 PM »

TP3 should be around -11VDC.
Check Zener D20. It could be dead.

19

CP5176 FET compressor / Re: GR Meter not lighting up, D8 and D16 LED shows a short between pads

« on: April 06, 2024, 04:35:33 PM »

Look for solder bridges or reversed IC's.
If the issue was in U4, the LED's 1 to 8 should work.
Check that you get the power voltages on the IC's pin3 (+15V) and pin12 (-15V).
Check that you get some control voltage on pin 5, 7, 9, 11 of the 4 IC's.

20

CP554 Diode bridge compressor / Re: Can’t get 3v in step 5 in setup

« on: April 06, 2024, 04:11:31 PM »

But I only see 0.064vDC across TP2 and TP3.

(Without left PCB installed)
Check the connections to the output transformer.
What DC voltage do you get on the yellow wire, against 0V ?
What DC voltage do you get on TP3, against 0V ?
Check the solder joints on Q7, trimmer TR2 and R31.

21

MP566 Tube microphone preamplifier / Re: MP566 not working

« on: April 04, 2024, 03:09:35 PM »

Contact me here:
https://www.soundskulptor.com/en/content/6-contact

22

LA502 Optical Compressor / Re: Gain Reduction Meter & Compression is extremely sensitive

« on: April 04, 2024, 03:08:29 PM »

100k for peak
100kB Log ?

What is your 0dB input signal voltage level?
If you are working at a high level, higher than +4dBu, it can be useful to decrease the gain in the side chain by increasing the value of R20 (in PCB REV1.4).

23

CP4500 Stereo Bus Compressor / Re: Compression happening randomly

« on: April 04, 2024, 02:57:05 PM »

This looks a lot like an intermittent solder joint. One way to find it is to tap the different components with a pen to try to provoke it.
You will probably need an extension cable.

24

MP566 Tube microphone preamplifier / Re: MP566 not working

« on: April 03, 2024, 03:58:01 PM »

New testing sessions, new results
I am puzzled. I will recommend you again to send it to us.

25

MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme

« on: April 03, 2024, 03:44:32 PM »