11

MU524 Vari-Mu Tube Compressor / Re: No AC volage from TP1 on

« Last post by JPK on April 11, 2025, 09:54:00 AM »

12

MU524 Vari-Mu Tube Compressor / Re: No AC volage from TP1 on

« Last post by coostor on April 10, 2025, 10:57:38 PM »

U6 had to be replaced with a new one. No voltage came out at the output. 
After replacement everything works perfectly, all measured values are correct.


Thank you for everything,
C.

13

MU524 Vari-Mu Tube Compressor / Re: No AC volage from TP1 on

« Last post by JPK on April 07, 2025, 05:41:23 PM »

Did you check the glowing in the dark? Because it is not very visible in daylight.

Power up the lunchbox: 5,5 V then more to 6.2 V after 10 seconds.
Do you confirm this? Check the solder joints of the tube socket and the header connecting the tube PCB to the main PCB.

14

MU524 Vari-Mu Tube Compressor / Re: No AC volage from TP1 on

« Last post by coostor on April 06, 2025, 08:59:19 PM »

The values, directions and soldering of L1, L2, U6, C30-C33, D9, R38, R39, Q4 are correct.
I have no idea what the problem could be...

15

MU524 Vari-Mu Tube Compressor / Re: No AC volage from TP1 on

« Last post by JPK on April 04, 2025, 10:05:48 AM »

Check value, dirction and solder joints of L1, L2, C30...C33, R38, R39, D9, U6, Q4.
In particular, make sure U6 and Q4 are in the correct direction:
- Pin 1 of U6 towards L2, coil facing T1.
- Writings on Q4 towards R39.

16

MP512 Microphone preamplifier / Re: LED activity reflected in sound

« Last post by Mar on April 02, 2025, 09:35:12 PM »

It has to be something on the DI side of things. When I am going DI on my other pre and coming out into the mic input of the 512 at the back problem goes away. I use DI a lot, this unit didn’t bring me a lot of joy. Not wasting any more time on it.

17

MU524 Vari-Mu Tube Compressor / Re: No AC volage from TP1 on

« Last post by coostor on April 02, 2025, 04:14:38 PM »

I measured it wrong, the resistance is 3.4 ohms.
I tried it with a telefunken ecc189 tube, there is no difference in the result.
It doesn't glow and VAC values are zeros.

18

MP512 Microphone preamplifier / Re: LED activity reflected in sound

« Last post by JPK on April 02, 2025, 03:18:19 PM »

Can you try to reproduce the effect with pulses of sine wave coming from a generator pluggin?
This is because I don't understand how it could be caused by the preamp.

19

MP512 Microphone preamplifier / Re: LED activity reflected in sound

« Last post by Mar on April 01, 2025, 07:43:07 PM »

Here it is. Dry guitar followed by a bass https://limewire.com/d/zfSxT#MU82BZAeTL

20

MU524 Vari-Mu Tube Compressor / Re: Tube PCBs

« Last post by AcdNrg on April 01, 2025, 04:23:53 PM »

Thank you!