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Messages - JPK

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1
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.

2
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)?

3
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.

4
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!

5
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.

7
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.

8
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.


9
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.

11
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).

12
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.

13
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.

14
MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme
« on: April 03, 2024, 03:44:32 PM »
👍

15
CP5176 FET compressor / Re: noise/hiss on output (again)
« on: April 03, 2024, 03:43:43 PM »
The noise could be caused by a HF oscillation. Check that C9 and C16 have good solder joints.
An oscilloscope could be useful here.
It could also come from the input transformer. It is a 1:1 ratio so the compressor could work without it. You can try to remove it and send an unbalanced signal to pin 8.

16
Check that you didn't swap the 2 pots:
PEAK : 100kB
GAIN : 4k7C

17
CP5176 FET compressor / Re: noise/hiss on output (again)
« on: March 29, 2024, 04:04:10 PM »
Check the potentiometer P1: center pin to each side pin going from 0 to 10k.
Check the DC resistance of primary and secondary of the input TX: 2k2 : 2k2
Check the connection between TX case and 0V
Check the solder joints of the transformer.

18
MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme
« on: March 26, 2024, 05:33:03 PM »
Quelles mesures à faire sur le transfo
Résistance entre pin1 et pin4 : 38 ohms
Résistance entre pin5 et pin8 : 3.2 kohms
Pas d'autre connexion entre pins ni avec le boitier.

comment tester le relais ?
Tester les connexions. Vérifier l'absence de connexion anormale

19
CP5176 FET compressor / Re: noise/hiss on output (again)
« on: March 25, 2024, 06:31:51 PM »
Do you get the correct DC voltages (A to G) on the preamp?

20
MP566 Tube microphone preamplifier / Re: MP566 not working
« on: March 25, 2024, 06:01:16 PM »
With U4 inserted, U4-pin4 = 2.86V
With U4 removed, U4-pin4 = -15V
Weird! U4-pin4 is connected to the V- rail.
Can you check the continuity between U4-pin4 and the V- test pin?

Do the voltage values on V- and V+ remain correct when U4 is in place (-15V, +15V)?

21
MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme
« on: March 25, 2024, 05:41:14 PM »
Un pont de soudure sous le relais, un pb sur lr transfo ? Tout est possible.

22
MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme
« on: March 24, 2024, 04:02:21 PM »
Est-ce que ce pourrait être un relais défectueux ?
Possible. Attention à ne pas abimer les traversées en retirant les relais.

RLY1 aiguille le signal Micro/DI.
RLY2 est un attenuateur -20dB pour la position LOW gain.

23
MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme
« on: March 24, 2024, 09:30:48 AM »
Je sèche. Je pense qu'il va falloir nous l'envoyer.

24
MP512 Microphone preamplifier / Re: Problème d'alimentation fantôme
« on: March 23, 2024, 06:40:18 PM »
Il doit y avoir une erreur de numérotation.
Pouvez-vous recommencer en suivant cette image ?

25
MP566 Tube microphone preamplifier / Re: MP566 not working
« on: March 23, 2024, 06:30:49 PM »
Can you measure the DC voltages on the 8 pins of U4, without U4 inserted?

Will it ever work?
Sure!
You can always decide to send it to us for a repair.

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