Quote from: Jazz P Bass on April 15, 2024, 10:56:14 AMYour serial number indicates a manufacture date of June of 1975.
The schematics that you found are from 78 & 79.

Thank you for the info about the manufacture date! Seems to be the first version of the JC-60 then. I read somewhere that they started building the jc-120 and the jc-60 in 1975.

Your serial number indicates a manufacture date of June of 1975.
The schematics that you found are from 78 & 79.

Quote from: g1 on April 14, 2024, 02:44:32 PMThe service manuals usually go by serial number, what is it?

The serial number of the amp is #430830.
In the service manual is a note that for the JC-60 its for #787100- and for the JC-60A R&P its for #810530-. It was first printed on March 31. 1979 and its the fourth edition.
The amp is a earlier version, it has a different circuit board, different power transistors and has less control inputs on the back. i couldn't find the right service manual for my version. just the one mentioned and newer ones.
Does anyone maybe have an earlier service manual?

Quote from: saturated on April 14, 2024, 01:45:56 PMWow nice amp 

Welcome to the forum

 

Thank you!
 

The service manuals usually go by serial number, what is it?

Wow nice amp 

Welcome to the forum

 

added pictures

Hello everyone!

I recently got a broken Roland Jazz Chorus 60 for cheap. It seems to be a pretty early model, because I couldn't find any similar ones by searching the web (pictures added). The previous owner told me that it stopped working like 20 years ago and that a friend of him tried to fix it with no results. two or three components are missing with burn marks on the circuitboard. Could be normal- or the fusing-resistors I think. I think he tried to exchange them, without changing the actual problem so he burned the circuitboard. I think it should be an easy fix to retrace the little burned parts of the circuitboard. But my problem is that I can not identify the missing components cause I'm not very good in reading schematics and identify the traces on the circuitboard.
The main problems which caused the components to burn out, are probably the old transistors so I ordered new ones.
for the 2SC1628Y I ordered a SC3503 and for the 2SA814 and the 2SC1624Y I ordered a MJE15030 and a MJE15031.
now my question is: has anyone seen this version of the Roland JC-60 and can identify the missing parts? and are the ordered transistors the correct replacement?

I've added pictures of the amp and the circuitboard plus a schematic for a different version of the JC-60, which seems ok for the power amp circuit.

thank you!









https://ibb.co/W6ZC157

I think your meter is trying to average the AC voltage on the two inner pins.
Try with the meter set to to Volts AC.

Ok guys sorry for the bo bo 

Anyhow removed the old one (no easy task) and got a new one in

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Seems all is good when measuring the (+) pin and two middle pins (~)

(+) pin reads about 40v DC (have no idea what it is supposed to be


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But when I read the middle pins I get like 16v ac but what the heck I get 20v DC

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I think I'll call it a night