1

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: September 18, 2025, 06:48:38 PM »

Thanks a million, definitely taking notes on my mistakes.

2

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: September 18, 2025, 04:39:22 PM »

My unit should have arrived late last week. Do you have an eta when you or your staff will be able to take a look at it?

3

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 27, 2025, 03:45:16 AM »

Pretty much spot on. Goes to about 2.VDC in about 5 seconds & within 10 seconds goes to 6.43VDC and is stable.

At this point I think I am ready to send it to your lab , just let me know the best way to do so. I'm bummed but this is obviously beyond me. Either a faulty part or a faulty installation of one by me somewhere.

4

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 26, 2025, 04:19:53 AM »

Input transformer is in correct orientation.

TR1=202 2k
TR2=102 1k

B+ stable at 45.5VDC

R3= 3k3
R4= 3k3  
R5= 10k 
R6= 10k  
R7= 10k  
R8= 470R 
R9= 10k  
R10= 10k  

input transformer values (input on max)

2-4= 37.2 ohms
3-5= 37 ohms
7-9=100.1 ohms
8-10= 99.1 ohms

input resistance pins 2&3= 4.61 k ohms

everything mostly checks out excepts input transformer 8-10 being 99.1ohms. 

5

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 25, 2025, 12:23:33 AM »

Unfortunately it does not appear a tube swap made a difference in stabilizing the voltage.

6

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 23, 2025, 06:39:50 PM »

okay now with black probe on 0V I'm reading :

V1= 15.68vdc
V2= -15.65vdc

all my tests between TP1 & TP2 have been after at least 15-25min of warming up.

TP1 & TP2 after 30min and U4 still removed varies between +-1 to 2 hundredths of a VDC. 

With U4 replaced shortly after shut down of last test and waiting another 30min I am seeing my DMM with fresh batteries jump around again not stabilizing between 0.00 to +-0.05 VDC. Unfortunately it takes twice as long to mostly stabilize than what I seen in my first kit and the setup recommendation waiting time. Is this to be expected?

7

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 23, 2025, 01:14:14 AM »

looks like I am stable at the v+ although I am now noticing its reading negative instead of positive 15.6vdc, V- reads 15.5vdc positive vs. the setup saying it should be negative.

V+= -15.6vdc
V-= 25.5vdc

with U4 removed
TP1 to 0V= 32.3vdc
TP2 to 0V= 28.4vdc
TP1 to TP2= maybe slightly more stable, but still jumps around from a few hundredths to a couple tenth of a percent of voltage +-

8

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 18, 2025, 03:39:35 AM »

UPDATE: my DMM keeps fluttering between 1-4vdc in small to large increments between tp1 & tp2. All the other prior tests seems to be working correctly. 

9

MU524 Vari-Mu Tube Compressor / Stuck on step 7

« on: August 18, 2025, 02:42:02 AM »

Got to step 7 with my latest kit and the voltage between tp1 & tp2 keeps jumping up and down by hundredths of vdc. I did let the tube warm for at least 15 mins before testing. What would cause the voltage to flutter? Is it possible it is the tube?

Thanks

P.S. I got the U6 part for the stereo right kit today, Thanks a million

10

MU524 Vari-Mu Tube Compressor / Re: Stereo Right Kit

« on: August 15, 2025, 07:21:36 PM »

How soon should I expect to receive the part?

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MU524 Vari-Mu Tube Compressor / Re: Stereo Right Kit

« on: August 05, 2025, 03:58:21 PM »

Thank You,

Do you need my address, or are you able to get it from my e-mail?

12

MU524 Vari-Mu Tube Compressor / Stereo Right Kit

« on: August 05, 2025, 01:00:54 AM »

I just received my MU524 Stereo right kit and it appears that the part U6 is the exact same as my Left/Mono kit. Is it possible to get the correct version of the U6 as what I received looks exactly the same down to the number values on the all the parts on the U6 on my Left/Mono Kit?

13

MU524 Vari-Mu Tube Compressor / Re: Step 9-10 side chain setup

« on: July 29, 2025, 01:39:56 AM »

Yes the value of TR4 is marked 502, and the R32 Value is correct.
Also I really missed the negative sign on my DMM, it was placed directly below the DC symbol and I didn't notice till I came back to it

the max value was something like -7.32

I just finished setting it up, Thanks for your response. I suppose I just needed to step away for a bit. I just ran music through it and it seems to respond like a compressor. I have not listened to it yet as I have not put it in the correct spot near enough to an input. I will come back if it does not sound correct (hopefully in the next few days as I am 40 yrs old and started back to college this summer and it's finals week).

Again thank you, much appreciation 

14

MU524 Vari-Mu Tube Compressor / Step 9-10 side chain setup

« on: July 27, 2025, 12:46:40 AM »

I cannot get my DMM to show -2 when adjusting the TR4 VREF. It goes to zero before the Trim pot starts clicking to let me know I've reached max adjustment. Am I missing something? 

Do I need to adjust the output potentiometer back to zero (instructions does not mention to do this)?

Also do I need to pick a sidechain setup step to go with(i.e. -3db @ -2v, or -6db @ -3.6v)?