21

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

« Last 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

22

MP573 Microphone preamplifier / Re: Bias Adjust

« Last post by JPK on July 01, 2024, 03:20:56 PM »

It is normal for the voltage to drop a little, around 100mV, as the unit warms up but it should stop when it reaches its equilibrium temperature.

23

MP573 Microphone preamplifier / Bias Adjust

« Last post by Evan Sabby on July 01, 2024, 12:57:10 AM »

I have a question about the bias adjust portion of the testing.

I place the positive (+) test probe from the DMM on TP4 and the negative (-) test probe from the DMM on TP2.  I power on the unit and adjust P2 until I read 3 volts.  My question is after I get P2 adjusted to 3 volts the voltage begins to drop very slowly and continues to drop over time.  Is this ok?  If not what do I need to do to fix it?

I appreciate any input.

Thanks,

Evan

24

LA502 Optical Compressor / Re: LA502 - PCB 1.2->1.3 C5 47p cap

« Last post by JPK on June 27, 2024, 05:53:11 PM »

No, not necessary.
This cap ensures better Common Mode Rejection Ratio (CMRR) in case the 2 caps differ in value.

25

LA502 Optical Compressor / LA502 - PCB 1.2->1.3 C5 47p cap

« Last post by rameau on June 25, 2024, 12:53:18 PM »

Hello,

I bought the LA502 PCB 1.2-Version and already did the mod for reducing noise.
In addition to that mod, there is an additional C5 47p cap at the input part of PCB 1.3 who's been missing in PCB 1.2.
Is it also recommed to add this C5 cap?
What exactly is the benefit of this cap in addition to the two 470p caps?

thanks!
best regards,
Guido

26

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

« Last post by JPK on June 23, 2024, 03:36:56 PM »

What is the DC voltage on each side of R8, against 0V ?

27

CP4500 Stereo Bus Compressor / Re: Meter Light not working

« Last post by JPK on June 23, 2024, 03:34:44 PM »

- Check the solder joints of CN4 and connector to wires connections.
- Check the solder joints of R100 and trimmer T4. Check the ohmic value of T4.
- Try removing Q1.

28

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

« Last 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

29

CP4500 Stereo Bus Compressor / Re: Meter Light not working

« Last post by yudamn on June 22, 2024, 06:03:57 PM »

Does the needle move when you take the measurement?

Yes it does. It moved to just below the 8db mark.

30

AB528 Microphone preamplifier / Re: Preampli AB528

« Last post by JPK on June 22, 2024, 03:51:06 PM »

Est-ce que vous entendez le clic du relai quand vous passez sur 300 ?

et aussi un genre de léger bruit d'oscillation
Vérifiez les valeurs et soudures des condensateurs, en particulier C2, C3, C4, C5, C7, C8, C11, C14, C16.