Obsidius preamp problems

V

Vildhjuggah

Member
When I turn on my obsidius preamp the distorted signal doesn't come through (only raw sound and some sizzle). If I flip the toggle switches a million times it will come through, but then I try to flip it to the ones I like (or again at all) it cuts out again. To get it to the setting I like and work at the same time it takes awhile. Also, when I switch the pedal off and back on it normally goes back to no distortion (only raw sound and some sizzle) coming through.
I honestly don't know where to start diagnosing this problem. I'd guess check the switches but this happens no matter which switch I flip so I honestly don't know.
 
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The DC voltages you measured on IC2 back on Sept 30th showed that IC2 was good and D1 & D2 weren't shorted. So I doubt that changing any of them out will fix things. With power off, measure resistance to GND on each side of R19. R19 is the 10K resistor next to IC3 pin 5. I'm starting to think we might have a short in that area.
 
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From either leg it reads around 1 meg (takes awhile to settle).
In one of the pictures it seems one of the legs is touching the cap but i moved it away just in case a while back.
 
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Well damn. Correct me if any of these statements are wrong.
You have signal at IC3-3.
You have a bigger signal at IC3-1 and how big it gets depends on the DRIVE pot.
Switching GRUNT does not affect the tone or volume at IC3-1.
You have more-or-less the same signal at the top of R17 (right-hand 6.8K) that changes volume and/or tone when you switch GRUNT.
The signal is weaker at IC2-3 and IC2-2.

Which is louder: IC2-3 or IC2-2?
 
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its working?

it was starting to cut in and out again while testing (specifically while poking ic3)

so i pulled ic3 out and then there was a short lead under the resistors beside it that i had never seen before (dont know if it was under ic3 the whole time or not, but i think at one point i pulled out ic3 cuz i decided to go ahead and clean it too way back before i had to wait for the switches i ordered to come in) so when i pulled the ic out a leg somehow jumped under the resistors, tried poking at it and it fell out so i kept looking to make sure it was gone, tried again cutting out then another footswitch wire broke loose and i soldered that back on, and now it seems to be working right

but now while the pedal is off but plugged in the light is flickering?

If it was that one little lead the popped out of nowhere this whole time im gonna be mad but also so sorry you've wasted so much time (though i have learned a good bit and you did tell me about the 2 capacitors that i put in the wrong spot)

im gonna test it some more to make sure its actually working now
and maybe the lead moved and is causing the flicker somehow but i cant find it
 
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You have more debris in there I'll bet. I recommend that you completely remove the board from the box, pull the ICs out of the sockets and try shaking out anything else that's stuck under sockets and parts. Trimmed leads, bits of stranded wire, solder balls, etc. If there is any sign of stickiness or flux residue, rinse the board thoroughly with alcohol. Otherwise, the conductive bits will get stuck in the sticky stuff, only to come loose and wreck havoc later on.
 
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