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JC-120H Expanded schematics/service manua

Started by willpirkle, May 27, 2021, 08:22:54 AM

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I've scored a JC-120H (head) and I have the '84 Schematic as it is called. It is only one page and I'm looking for the rest of it, including disassembly instructions, etc... is there more of the '84 schematic than just the one page? Like a more complete service manual?



Jazz P Bass

Marshall never was one to supply actual service manuals.
Schematic is all you get.



The older Roland 'service notes' didn't have that much in terms of disassembly, but they do have board layouts, waveforms, and some hardware.
They are organized by serial number, nothing really about the year.
You can probably find yours here:


Thanks! I actually had that batch, but noticed the head version was not in there, so I thought I'd ask to see if there was another source. Mine dates to 1985 according to the serial number. Gotta say that through my Marshall 1960, it sounds great. Even the distortion on this model is reasonable (not awesome, but also not horrific like the 120 twins I've tried over the years) and the preamp/distortion are just so simple in the head version.

I need to fix the reverb on this, which is only barely audible with the control on 10, so will open it up this weekend after verifying it isn't the footswitch jack. Thanks for all your help and input on everything. Guaranteed to learn something new and interesting on each visit here.