Sound Skulptor forums

Build help and troubleshooting => MU524 Vari-Mu Tube Compressor => Topic started by: aj99009 on June 10, 2024, 01:10:37 AM

Title: AudioPath Test Question
Post by: aj99009 on June 10, 2024, 01:10:37 AM: I'm new to building these kits. I'm on step 6 to test the audio path and when I send the signal I'm getting 0.003 vac on my multimeter. No matter what I change in my daw I can't get it close to 1.0 vac.
Not sure what I'm doing wrong here

Everything checked out good in the steps before.

Austin
Title: Re: AudioPath Test Question
Post by: JPK on June 10, 2024, 11:10:39 AM: No matter what I change in my daw I can't get it close to 1.0 vac.
Do you mean when bypassed?
If true, it is either a connection issue: check your connections from your audio source,
or you have a bad solder joint on the relay.
Do you hear the relay clicking when you move the bypass switch?
Title: Re: AudioPath Test Question
Post by: aj99009 on June 12, 2024, 10:11:16 PM: Yes when bypassed.

From my DAW I send a 1KHz at -11db
Unit is set at
In 10
Out 0
Rec. 10
JMP1 removed

My multimeter reads
when bypassed = .010
when in = .085
when in and out set to 10 = 3.655

I checked the solder joints on the relay and they look good
I hear it click when flipping the switch
Title: Re: AudioPath Test Question
Post by: aj99009 on June 12, 2024, 10:13:22 PM: When I bump the 1KHz to 0.0dB my multimeter reads 0.039 when bypassed.
0.309 when In
10.99 when In and out turned to 10
Title: Re: AudioPath Test Question
Post by: JPK on June 13, 2024, 10:53:11 AM: What AC value do you read when directly connected to the source at 0.0dB, without the MU524 connected.
Title: Re: AudioPath Test Question
Post by: aj99009 on June 15, 2024, 06:11:02 PM: Ok so it was a issue with my chassis. Got the unit up and running now with no problems!

I do have another issue with the 2nd stereo R unit i built...

I run the signal bypassed and get the 1 VAC. But when I turn the unit on it kills the signal, 0.000 vac.
When I turn the out pot to 10 still 0.000 vac.

Ran through the tests and got this

TP1 290 mV VDC
TP2 203 mV VDC
TP1 to TP2 .215 VAC
TP3 to TP4 0 VAC
Output 0 VAC

with Jumper and out pot at 10
TP3 0 VAC
TP4 0 VAC
TP5 0 VAC
TP6 0 VDC
Output 0 VAC
Meter 0

The tube slow start test was good

Power voltage meter test was good
V+ 15.36
V- 15.31
B+ 46.3
Title: Re: AudioPath Test Question
Post by: JPK on June 17, 2024, 11:58:32 AM: What is the DC voltage, against 0V, on the test pin B+.
It should be around 45V.
Title: Re: AudioPath Test Question
Post by: aj99009 on June 17, 2024, 09:07:35 PM: B+ to 0V = 46.5
V+ to 0V = 15.3
V- to 0V = 15.3
Title: Re: AudioPath Test Question
Post by: JPK on June 19, 2024, 11:12:16 AM: TP1 290 mV VDC
TP2 203 mV VDC
These pins should be above 30VDC, against 0V.
Check the solder joints on R8.
Title: Re: AudioPath Test Question
Post by: aj99009 on June 22, 2024, 07:14:09 PM: So I checked R8. Looked good, re-soldered it to be safe.. All the solder joints on the unit look to be good.
Still no signal once unit is switched on
Title: Re: AudioPath Test Question
Post by: JPK on June 23, 2024, 03:36:56 PM: What is the DC voltage on each side of R8, against 0V ?
Title: Re: AudioPath Test Question
Post by: aj99009 on July 01, 2024, 04:40:16 PM: Ok so tested 0v to both sides of R8.

Lower side of R8 (toward the TP pins) reads 46.6
Upper side of R8 reads .607
Title: Re: AudioPath Test Question
Post by: JPK on July 02, 2024, 03:39:20 PM: The upper side of R8 should be at 46 Volts.
It is only connected to R6, R7 and C7.
Check these components. There must be something wrong here, like a solder bridge of a bad solder joint.
Title: Re: AudioPath Test Question
Post by: aj99009 on July 02, 2024, 08:13:28 PM: Found the problem.
I had R8 and R18 in the wrong spots.. Switched them and everything is working good now!
Rookie mistake..

Thank you for helping me figure it out!
Title: Re: AudioPath Test Question
Post by: JPK on July 03, 2024, 04:38:29 PM: (https://fonts.gstatic.com/s/e/notoemoji/15.0/1f44d/32.png)