41

MP573 Microphone preamplifier / Re: MP573 general power check and deviating DC voltages

« Last post by JPK on June 17, 2024, 11:53:59 AM »

42

CP4500 Stereo Bus Compressor / Re: Meter Light not working

« Last post by JPK on June 17, 2024, 11:52:10 AM »

First check that the meter is working by measuring its internal resistance (connector unplugged). This should move the needle. Around 600 ohms.

43

MU524 Vari-Mu Tube Compressor / Re: AudioPath Test Question

« Last 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

44

MP573 Microphone preamplifier / Re: MP573 general power check and deviating DC voltages

« Last post by Gavin1393 on June 15, 2024, 11:52:41 AM »

In lesser company I might have argued that there was nothing wrong with my soldering, since I'd used Flux on every joint, perfected my technique...but there it was Q6 and its three pins, two attached to the board and one, like the Wright brothers, had lifted off the board. OR, I just soldered it to mid-air...

Soldered it correctly and sheepishly considered all the other joints in the area, and they are looked good.

Pulled out the DMM... and got near perfect results for the voltage test. Adjusted the P2 and got 3.000v after a good few turns with the blue tool JPK sent me.
Plugged in the Mic's and SOUND!Glorious SOUND!
Did all the other checks and all seems delightfully positive!

Thanks JPK

Appreciate the guidance - as always, you were spot on with where to look! I think it took me all of 30 seconds to see the problem once I knew where to look!

45

CP4500 Stereo Bus Compressor / Re: Meter Light not working

« Last post by yudamn on June 14, 2024, 10:28:43 PM »

Hi.  I've tried to live without the meter working, but it's beginning to get to me. It's the same issue, the compressor works, the meter lights up, but the needle doesn't move.  I've checked that the meter connector is properly connected.  Also the meter worked for weeks before it stopped.  Is there something specific that I should be looking for?

46

MU524 Vari-Mu Tube Compressor / Re: AudioPath Test Question

« Last 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.

47

MU524 Vari-Mu Tube Compressor / Re: AudioPath Test Question

« Last 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

48

MU524 Vari-Mu Tube Compressor / Re: AudioPath Test Question

« Last 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

49

AB528 Microphone preamplifier / In case your AB528 doesn't work as expected

« Last post by JPK on June 12, 2024, 05:15:00 PM »

Check the usual suspects:

• Check you didn't leave the polarity switch on the center position (=mute),
• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Check the DC voltages:
First check the supply voltages as described in the setup guide.
Next, without any input signal, connect the voltmeter black probe to the 0V test pin and note the DC voltages you get at the points shown on the attached picture. Compare with the expected results (more or less 10%).

50

AB528 Microphone preamplifier / Re: Preampli AB528

« Last post by JPK on June 12, 2024, 04:08:10 PM »

Le problème se situe dans l'étage de sortie.
Vérifiez valeur, direction et soudures des composants Q3, Q4, Q5, Q6, R22...R29, C13...C18.

J'ai ajouté un topic pour les tests :
https://www.soundskulptor.com/forum/index.php?topic=498.msg2966#msg2966