My GSSL crapped out! Please help!

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six_wax

New member
Joined
Feb 24, 2006
Messages
3
The detector circuit seems to have gone bananas. Adjusting the Threshold has no effect on compression amount, except when full open/clockwise, which causes the audio to cut out... Seems like the Threshold input to detector is "stuck".

The original build was straightforward, and the unit had worked perfectly for months. I'm not sure how to go about finding the problem though...

Any suggestions as to what might be the problem, what to test/replace, etc?

Thanks for your help!
 
Bit of a long shot, but:

Voltage regulators (+/- 12V, probably) could be fried, (too hot to touch is a good diagnosis). You'd have to go through the looong help threads to get more info, I'm afraid.
 
Thanks for the replies! I figured I'd start by swapping out the Threshold pot and the TL072 in that path.

Full open on that Threshold pot should mean -12v at Pin2, correct? Guess I can get a Fluke in there to test that stage & get some idea what's up...

Had to happen in the middle of 4 mix projects... :?
 
Referring to this, ["THRESHOLD" input section Lower-Right corner]:

http://www.gyraf.dk/gy_pd/ssl/ssl_sch.gif

....

So the Threshold pot appears to be functional [smoothly variable between ~0-12mV across output].

The voltage rails [+/-12V] appear to be ok at the TL072 input.

220k resistor before Pin2 checks out ok.

The Pin2 input voltage doesn't change appreciably with Threshold, is this is a current-driven device? Oh wait, Op Amp... right.

Any more suggestions?

THanks!
 

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