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I work more in tube audio, but I'm working on a McIntosh MA6100 integrated amp for someone that has one bad output channel. One thing I'm noticing on the driver board is that there are three transistors on it apparently from original construction that are not on the schematic circulating online. The electrolytics have been replaced by a prior tech, but one value is different from the schematic, so I don't know if it was a revision or someone using what he had on the shelf to get the repair out the door.
Googling service bulletins for this model turned up a couple of minor issues, but not the circuit board revisions I'm seeing. The schematic mentions some revisions that appear on this board (diodes in place of resistors used in earlier models), but not the extra transistors.
I've contacted McIntosh, but haven't heard back.
Edits: 03/29/17Follow Ups:
I can't imagine a company with the chops of MC making major UNDOCUMENTED Revisions.
Too much is never enough
McIntosh did send me a later schematic that shows the revisions I found. The schematic on pretty much every website out there is one from an earlier version. There were some revisions to the input of the power amp, mostly minor.
over in "Vintage"
"Man is the only animal that blushes - or needs to" Mark Twain
Also post this over at AudioKarma's McIntosh group. Some of those guys know a LITTLE TOO much about these amps.
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