PLEASE NOTE: The person that scanned this apparantly thought it was a JC-120 schematic and labled it as such, however it is really a JC-77 amp.
You can tell by the single channel and the hi-treble pot.
By the way, this schematic is from 1984 and I am sure that you probably know that Roland made quite a few changes to this circuit over the years.
It may not be identical to the amp that you have.
As far as I know, that IS indeed a schematic of a JC-120. Not the combo model, though, but the head.
See:
- The same power amp circuit as in most JC-120's (wouldn't make any sense if it was a schematic for the lower power JC-77 version)
- Sub in jack and four speaker output jacks. No such things in JC-77 but indeed found from JC-120H.
- No speaker depicted in schematic although all Roland's JC-series combo schematics depict them.
- Overall the same features that the JC-120H head has (which are also features shared by the JC-77, hence the confusion)
I'm sorry to say it, I believe that is not the right schematic for JC-77.
Hopefully it will help, though because likely the preamp design in both is very similar.
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