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mypantsrblue

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Mar 26, 2021
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I am going to do a test today with the jumpers, but if the VCAs were bad(or at least the one in the sidechain), which it sounds like they should be, shouldn't the unit not be compressing and the ratio / attack / release all not be working? Maybe I misunderstand the circuit?
I did the test and here is my report:

When jumping pins 1 and 8 on the left and right VCAs, the compressor still behaves as normal in terms of meter reading etc, but there is no sound output still.

When I do the same jumper test on the sidechain VCA, the meter no longer behaves normally. I think this answers my question that the metering would not work with a faulty VCA, so does this mean my VCAs are actually OK, is there any other way to test?

Moving forward for next steps, I notated that pins 1 and 8 on the left and right VCAs are all seeing around 7 volts (the other 6.8).

Let me know what else I can test to narrow down where the signal goes bad!

Thank you so much
 

Script

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Nov 26, 2008
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You had checked for correct DC voltages +/-15V and +/-12V on all IC socket pins before inserting any of the ICs, right ? If not, maybe it's time.
 

mypantsrblue

New Member
Joined
Mar 26, 2021
Messages
16
You had checked for correct DC voltages +/-15V and +/-12V on all IC socket pins before inserting any of the ICs, right ? If not, maybe it's time.
I did not. I followed the “beginners guide” which only had me check that I had 15V coming off the toroid before installing ICs. I’m working with a 95% understanding (maybe 50% of the actual circuit) and a strong ability to follow directions which, I guess is why this build mostly works. Thanks so much for helping me

Just To confirm i understand….I should be checking the pins on each IC that are V+ and V- ? And looking for them to be +/- 15V or +/- 12V? How do I know which should be which?
 

Script

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Joined
Nov 26, 2008
Messages
1,513
Location
Japan
Search net for datasheets.

Or search for

'"IC number, eg. 5532] pinout"
under /mages/

sidechain 12V
audio path 15V

Check all socket pins.
 
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