Need schematic diag Roland JC120

Amptek · 10-18-2007, 11:46 AM

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 · 04-21-2008, 11:10 PM

Mike

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

cheers

vintagekiki

Enzo · 04-22-2008, 12:37 AM

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.

10-18-2007, 11:46 AM	#1
Amptek Junior Member Join Date: Aug 2006 Posts: 6	Need schematic diag Roland JC120 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

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04-22-2008, 12:37 AM	#3
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	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.

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