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Lab5 Compressor not engaging

Started by nosaj, August 14, 2023, 06:06:28 PM

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i have a Lab5 that seems to be having a issue with the compressor not engaging. The way I understand it compressor rolled all the way to the left at -18 should be the most sensitive but it doesn't seem to matter any position of the compressor knob. it just doesn't work. Any help I can get would be greatly appreciated.
When powering on sometimes it will light for a sec then go off so the LED is good.

Jazz P Bass

Are you getting a signal through A112 pin 7 & 1?


I have an L5 amp.  What I've found is that the master volume needs to be turned up to at least the 10 o'clock position before the compressor will engage.  See if that works for you.  Of course one problem if you do this is that, at 100W, it's a loud amp!


Mybe spray some DeoxIT in the slide switch and work it for a bit to clean the contacts.
There are no stupid questions.
There are only stupid mistakes.


Quote from: Jazz P Bass on August 16, 2023, 11:43:22 AMAre you getting a signal through A112 pin 7 & 1?
Sorry for the delay guys.  I will pull out the scope tomorrow and check signal.

I followed these procedures for setting compression and nada nothing.
Dummy load
all tone set flat
master CW
Compressor off
Dial up till output reaches 28.3 VRMS with 1khz sine 100mv into low jack
Turn compressor on set to zero adjust r186 till led starts to fire.

thats the instructions from the lab series notes.
Will check on signal tomorrow and flush slide switch and pots.

Thanks guys


How can I make notifications pop my email when theres a response?


Quote from: Jazz P Bass on August 16, 2023, 11:43:22 AMAre you getting a signal through A112 pin 7 & 1?

Yes i am getting signal on pins 1 and 7.



 They have range of DC voltage at Q101 source shown (.5 to 2V), I think that should follow the pot setting.
(copy/paste from MEF  ;) )


Well dang.  i hooked up  to c138 to measure the range of voltage from q101 and what do you know compression led lit up. So i had a cold joint .
Looks to working just fine now. Set the compression circuit and and now works as it should.

Hi's a Fives to everyone.