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Re: GReg/Electrical Tech Journal

Postby greg on Fri Feb 02, 2018 6:52 pm

Studer A820MCH blacksides-

Channel 4 has dc spikes when recording tones, monitoring off the repro head. The spikes are not recorded. When it happens, channels 1-3 are effected in weird ways, muting, changing level, etc.


Problem followed the repro card, when I moved it to channel 8, including the side effects to channels 5-7 suggesting some corruption of the CMOS bus to the set of 4 channels ("bus converter 4 ch" board distributes the CMOS in sets of 4 channels).
Replaced all the chips that are connected to the bus. In the past, a bad chip has caused similar problems- not better
Replaced all the amplifiers, starting with the ones directly related to the signal path- nope
Removed IC 6, which would prevent any possibility that the sync repro signal path could be leaking into the repro path- nope
The board has been recapped already.
One clue, the sine wave starts to distort and triangulate just before the pop occurs.

Working with a spare until there's another free day in the studio to test more ideas.
I'm going to get my heat gun and freeze spray and really torture the board under a scope.
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Re: GReg/Electrical Tech Journal

Postby greg on Fri Feb 02, 2018 6:54 pm

Nate Dort wrote:I figured. I think I've actually posted that part number in another thread around here, but never bothered to order one.

I actually work for Harman, but I have no contact with the AKG folks, so they might as well be a separate company.

Maybe you can get an employee discount!

Email me if you need the guy I contacted.
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