Need schematic diag Roland JC120

[Amptek]

Hi !

I need the schematic and layout diagram for a Roland Jazz Chorus model JC120 Serial number 451,181 manufactured by Roland (early 1978 model) with the TO3 output transistors. (3 boards: CH1, CH2 with dist, section and Chorus board)

Hi have a distortion problem on CH2. Channel 1 is OK. It's a strange problem. I checked all transistors (2SA493, 2SC1628, Q22, 2SC1624, 2SSA814, diodes and 1S1555 diode ----> are goods). As soon as the speaker is connected (ch 2) ... the distortion appears ... when speaker is disconnected ... the distortion dissappear ...

Can you help me http://music-electronics-forum.com/i...s/confused.gif



THANKS !!!
Mike
Amptek
cablespec@3web.net

[vintagekiki]

Mike

here is three diferent schematics for JC120. once is your.

cheers

vintagekiki

[Enzo]

If the output waveform looks OK without a load but collapses with a load, look to the output stage not being able to supply enough current. make sure none of the ballast resistors - "emitter resistors" - are open, remove the outputs and test them out of circuit. Note which side of waveform is collapsing.