Sound Skulptor forums

Build help and troubleshooting => MU524 Vari-Mu Tube Compressor => Topic started by: forcemusicgroup on February 17, 2023, 06:28:41 AM

Title: VARI-mu build
Post by: forcemusicgroup on February 17, 2023, 06:28:41 AM

Having issues with build  - 

Going on step 5-6 - tube isnt really warming up - (not as warm as ive felt others) 
Sound is passing - Oddly When input pot is turned up - the volume goes down.
The meter lights up just fine. Output pot does give gain. haven't had a chance to test the recovery. 
I've done readings on all test points 

The reading goes as follows:


V+ 15.69
V- -15.74

TP1 - 40.59
TP2 - 40.05
TP3 - 0
TP4 - 0 
TP5 - 0
TP6 - 0

PLEASE ADVISE..

Thanks keenan 

Title: Re: VARI-mu build
Post by: JPK on February 18, 2023, 11:58:05 AM

Do you get the power up sequence correct? And 6VDC between the side pins?
the voltage slowly increases from 1 to 2V as the tube gets hot then more rapidly to 6V after 10 seconds.

Check in the dark to see if the tube gets redish inside.

Title: Re: VARI-mu build
Post by: forcemusicgroup on February 19, 2023, 03:14:17 AM

the voltage stayed around 2v.... maybe I was too anxious... ill look again...

Title: Re: VARI-mu build
Post by: forcemusicgroup on February 19, 2023, 03:28:37 AM

after 10 secs??? then no its hanging around 2.4 vdc

Title: Re: VARI-mu build
Post by: JPK on February 20, 2023, 09:31:53 AM

What DC voltage do you get between V- test pin and the right side pin of the tube holder PCB (marked H).
Is the transistor Q4 getting hot?
Check that no electrolytic cap is reversed (in particular C32, C33).