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91
MU524 Vari-Mu Tube Compressor / Sudden appearance of noise that will not go away
« Last post by DaftFader on February 19, 2024, 04:41:42 PM »
I've built and been using a pair of these for some weeks now without major issue, but suddenly in this session I'm working on the left compressor started to randomly make some bursts of noise. It would go away after a bit then come back, and eventually it became constant. And now I get a constant noise on my left comp which gets louder the more I turn up the output gain. It also goes away if I put it in bypass (although, when it first started doing bursts, I'm not sure if it did go away in bypass, I think it's only now it's constant that bypass removes it, but I'm not 100% sure about that as when it was making burst of noise I was running it into a bunch of saturation and clipping, so even the noise floor was audible and it might of just been that in bypass I was hearing, but I tested it afterwards and bypass makes it go away). Also If I put it into "LINK" mode it's the same as "IN" mode and the noise is there.

Here is a recording of it with both input/output dials roughly half way.

https://we.tl/t-7hnRoujobX

Thanks
DF

92
Yes. With an input signal of 0.1VAC, I get the following between pins 2 & 5:

Before sound disappears:
0.14VAC

After sound disappears:
0.00VAC

It also drops to zero.
93
MP566 Tube microphone preamplifier / Re: MP566 not working
« Last post by heimito on February 18, 2024, 11:38:19 AM »
1 -14,49 V
2  12,78 V
3  12,00 V (1 times sparks, when touching the pin )
4 -15,01 V
5 -5,677 V
6  12,53 V
7  12,55 V
8  2,850 V
94
DI503J Triple DI and Re-Amp / Re: Crunchy sounding Preamp pot
« Last post by DaftFader on February 17, 2024, 05:19:48 PM »
Just a follow up, the contact cleaner seems to of helped, I'll keep monitoring it and report back if it deteriorates again. I have a ton of contact cleaner though, so as long as it lasts a fair while before oxidizing again, I'll be ok to just keep giving it a toot of the spray every once in a while. 

Ta!
95
MP599 Microphone preamplifier / Re: MP599 preamp not working
« Last post by jasperdany on February 17, 2024, 02:21:13 AM »
Hi,

I replaced with another DOA, which I already have and I must say the mp599 sounds so good ;D, but unfortunately my DI (High Zi) is not working. When I connect my bass guitar, the XLR input behind, gets cut, that works fine (I can also hear the relay click when I insert my HiZi cable), I do not see any input signal. Is there any thing I could do ? :-\
96
CP554 Diode bridge compressor / Re: CP554 can't pass Setup process point 6
« Last post by kotrag on February 16, 2024, 07:33:27 PM »
Hi JPK  I did the test:

- U1 pin 14 (0VDC), - Yes
- U1 pin 7 (0VDC), - Yes
- U1 pin 8 (0VDC), - Yes
- Q2 collector (the pin closest to U1) (? 4 VDC), Yes - 3.49 VDC
- Q4 collector (the pin closest to C6) (? 4 VDC), Yes - 3.55 VDC



thank you so much!
97
CP554 Diode bridge compressor / Re: CP554 can't pass Setup process point 6
« Last post by JPK on February 16, 2024, 05:14:40 PM »
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).
98
MP573 Microphone preamplifier / Re: MP573 general power check and deviating DC voltages
« Last post by JPK on February 16, 2024, 04:44:37 PM »
Can you do the same test on the input transformer primary, between pins 2 & 5 ?
99
CP554 Diode bridge compressor / Re: CP554 can't pass Setup process point 6
« Last post by kotrag on February 16, 2024, 11:52:12 AM »
I was wandering about the unit, does it have to be switched on for these tests, or bypassed in order to get these values?

What could be the possible reason for not receiving the 4.7VAC between TP1 and 0V? 

Thanks!
100
Okay, I've now sent a sine signal with a generator plugin into the preamp. I only managed to send an input signal of 0.1VAC measured between pins 2&3 of the input XLR.

Measurements before the disappearance of sound:

  • Input transformer pin 7: 0.59VAC
  • TP1: 3.31VAC
  • Output transformer yellow wire: 6.24VAC

Measurements after the disappearance of sound:

  • Input transformer pin 7: 0.00VAC
  • TP1: 0.00VAC
  • Output transformer yellow wire: 0.00VAC

They all went to zero. The voltage starts to drop very slowly, and suddenly it drops quite fast.

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