1

MU524 Vari-Mu Tube Compressor / Re: something wrong with my build

« on: April 19, 2025, 11:37:18 AM »

found it. Works like a charm now and sounds amazing. It was a bad soldering at T1 and TR1 was bad. really happy thanks again.

2

MU524 Vari-Mu Tube Compressor / Re: something wrong with my build

« on: March 31, 2025, 09:01:08 PM »

Hi JPK, Rly is in the correct direction. I'm traveling now for 2 weeks, so I can't do the other checks when I'm back and the mu524 is not miraculously working I'll post again. Thanks so far.

3

MU524 Vari-Mu Tube Compressor / Re: something wrong with my build

« on: March 28, 2025, 08:16:52 PM »

sorry I'm stupid I measured the wrong pin, 5 instead of 8 so clear that there was 15v. 
the good measure is pin 1-8 0.145 vac no dc.

4

MU524 Vari-Mu Tube Compressor / Re: something wrong with my build

« on: March 28, 2025, 12:11:36 PM »

sorry, wrong measurement.
I measure on U2 pin 1-8 9vac and 15vdc

5

MU524 Vari-Mu Tube Compressor / Re: something wrong with my build

« on: March 28, 2025, 10:54:35 AM »

Thanks,
the signal on pin 1-8 of U2 goes from OL to 9vac. I changed U2 but that didn't help.

6

MU524 Vari-Mu Tube Compressor / something wrong with my build

« on: March 21, 2025, 07:50:22 PM »

when I turn Mu524 on my Vac level on the output drops. I can get it right by turning up tr2, but then when I have to match tr 1 and tr2 to  0 volt  I have to turn ytr2 down again and my output level is gone.
I changed the to transistors Q1 and Q2 to be sure they where not the problem but that didn't help.
this are the other voltages. The voltages on the tube sides and v+, v- and b+ are all correct.

A in =  1khz 1.0 vac
tp1 30.6 dc
tp2 30.6 dc
tp1 1.45 vac
tp2 1.45 vac
tp3 1.8
tp4 1.8


 
output 0.141 vac
 
B in = 1khz 0.3 vac
tp3 0.02 vac
tp4 0.25 vac
tp5 0.24 vac
tp6 0.002 vac
 
output 0.5 vac
meter 0

checked everything again can't find any misplacement. Also resoldered the input trafo.
any idea's what I could check else please.