Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hi there,

I'm working on an early production (mid to late 70's) Roland JC 120 Jazz Chorus (chrome corners, white label speakers, no bright switch, no FX Loop, no SN#).

All 4 input jacks (Low and High on Ch 1 and 2) are busted to pieces, to the point where I can't tell what type of jacks they are (how many pins they are supposed to have), and how they are supposed to operate within the functionality of the amp.

I can't find the correct schematic, and I can't find a relevant part number for those input jacks, so I'm stuck.

Best I can figure is that they might be "switched" jacks, they could have had up to 8 pins (based on what I can see - but maybe these were replaced with what someone else had on hand at some point...), both "High" inputs seem to be using a total of 4 pins, and the "Low" inputs seem to be using 6 pins.

This amp is a bit out of my repair experience, as I usually just work on old tube amps with no channel switching, but I want to figure this one out. I just need a little help.

Does anyone know what type of input jacks this amp uses? Please let me know if you have any helpful info for me.

Thank you.

Can you post a pic of the jacks?

One thing is the jacks must have insulating washers. Otherwise they will oscillate. 

Do jack pins go straight into PCB or they are wired to it?

Also asking for a picture.
Both of the jack remains and PCB itself.

Top and bottom closeups may let us "lift" the actual schematic (at least for the input section) by seeing what goes where.