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Messages - JPK

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MP566 Tube microphone preamplifier / Re: MP566 not working
« on: March 06, 2024, 11:13:54 AM »
removing U6 was not possible without destroying it.
To remove these 3 pins devices, simply heat the 3 pins together with a large blob of solder.
You can replace >U6 by this R-7812-0.5 or this PXO7812-500-S

I removed U6* --> 0,0V on U4 Pin 1
Not good. U4 might be dead again.

Sure. A bad solder joint can completely compromise operation.

I agree if you have the same issue on both units.
The relay switches the module XLR output between XLR input and compressor output.
Check if you don't have a short circuit on the output, between hot and cold or beween any phase and ground.

Not normal at all!

Can you remove the relay RLY1 in case it is defective?
Without RLY1 you won't get an output on the XLR but you should have a signal on TP1, TP2.

MP566 Tube microphone preamplifier / Re: MP566 not working
« on: March 04, 2024, 04:43:09 PM »
remove U7.
Check if U4 pin1 goes up to +12V now.
If not OK U6 is probably dead. Remove U6 and check again U4 pin1. If OK U6 is surely dead.
If OK look for a short circuit between TP8 and V- (tube removed).

The red LED switching level depends on R48, R49, R50, R51, R53, R54.
Check if these resistors are in their correct spot.

EQ573 Equaliser / Re: Glitching high shelf rotary switch
« on: March 02, 2024, 03:27:03 PM »
Probably a faulty switch. Please contact me.

MP599 Microphone preamplifier / Re: MP599 preamp not working
« on: February 26, 2024, 11:24:50 AM »

MU524 Vari-Mu Tube Compressor / Re: Light Hiss/Noise
« on: February 26, 2024, 11:24:11 AM »
Any ideas why this might be?
Does the noise also decrease if you remove the cover plate completely?

This kind of behavious sometimes come from a HF oscillation somewhere. Check the solder joints on all film and ceramic capacitors.

I suppose that firstly I have to figure out why I can't get any input signal
I am not sure about the ICs and transistors
The part name is marked on the devices. You must check them.

the conrad relay is the correct one despite their photo which does not correspond

Is this a problem?

EQ573 Equaliser / Re: EQ573-II noisy in pre mode
« on: February 21, 2024, 03:58:58 PM »
Does the signal/noise get better if you increase the input level of the EQ with the gain rotary switch on the preamp?
Try maximizing the level on the gain switch (and reducing the level with the +/-10dB pot).

MP599 Microphone preamplifier / Re: MP599 preamp not working
« on: February 21, 2024, 03:52:11 PM »
Yes to both.

I accidentally touched the corner of RLY1 with the iron
This is most likely the cause of the failure.

You will need to remove the input transformer to change the relay. follow the guide here.
The relays are:
AZ850-24 or TQ2-24V or EA2-24NJ.

MP599 Microphone preamplifier / Re: MP599 preamp not working
« on: February 20, 2024, 10:07:02 AM »
both the diodes are soldered in the wrong direction
This is the issue for sure. The diodes may have survived.

Will 1N914 Signal diode work ?

When I place the final plate, it touches the top of Capacitor C9, is that okay ?
This is not a problem.

It could be one of the relays.
Is it the same in 300, 1200, line?
Is it the same from the DI input?

Try removing the jumper JMP1 and listen if it is still there. This would show that it doesn't come from the side chain.
Try tapping various components (tube, electrolytics, pots) with a pen to hear if it increases the noise.
Is the noise level dependent on the input pot, the output pot?

MP566 Tube microphone preamplifier / Re: MP566 not working
« on: February 19, 2024, 05:58:23 PM »
1 -14,49 V
7  12,55 V
8  2,850 V

With these values, the outpout pin 1 should be positive. 
If the values are correct then U4 seems to be dead again.

DI503J Triple DI and Re-Amp / Re: Crunchy sounding Preamp pot
« on: February 19, 2024, 05:48:19 PM »

MP599 Microphone preamplifier / Re: MP599 preamp not working
« on: February 19, 2024, 05:47:21 PM »
Check that you inserted Q2 in the right holes (position A).
Can you measure the signal from the DI input on the test pin TP4 (against 0V), measured with our AC voltmeter?

All this is correct.
Did you check the ususal suspects ?

The unit was supposed to be ON for the measurements.
Can you measure the DC voltages, against 0V, on :
- U1 pin 14 (0VDC),
- U1 pin 7 (0VDC),
- U1 pin 8 (0VDC),
- Q2 collector (the pin closest to U1) (? 4 VDC),
- Q4 collector (the pin closest to C6) (? 4 VDC).

Can you do the same test on the input transformer primary, between pins 2 & 5 ?

Do I need a signal generator or function generator
Yes. Or you can use your DAW and loop a sine signal or use a sine generator pluggin.

and an oscilloscope for this test?
A scope makes things easier but your DMM can do the job.

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