Roland JC160 Distortion

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Carlosraj

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Joined 2010
This JC160 amp belonging to a friend of mine has channel 1 working fine but channel 2 was dead. Upon checking I found R151(10ohms,1/2W) has blown. After replacing it, the 2nd channel is working, but the distortion has totally no effect, it is not working. I checked the switch and it is OK. The other problem is the chorus/vibrator. When the switch is in the centre, both speakers sound equally loud. When I select chorus or vibrator, one speaker sounds softer than the other and the chorus/vib has no effect. I have checked all the resistors, diodes and transistor on board and they seem OK. Can someone guide me where and what can be the problem . Attached is the schematic which looks similar to this amp

Thanks

Carlos
 

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llwhtt

Member
Joined 2008
R151 supplies the +15VDC regulator, it blew for a reason. The regulator supplies all of the opamps plus some more. Check the output of the regulator, Q29?, for 15VDC. Then check to see if any of the opamps are hot. A hot one is a bad one.

Craig

Also this is in the wrong forum.
 
Kay Pirinha

Kay Pirinha

Member
Joined 2011
R151 also is a fuse resistor. Make sure to replace it with an appropriate one. At least keep enough clearance to the PCB (don't cut the replacement's leads if you decide to use a common component).


It also feeds the +30V regulator. Measure the voltages at Q27's and Q11's emitters and report.


Best regards!
 
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Carlosraj

Member
Joined 2010
Kay Pirinha said:
R151 also is a fuse resistor. Make sure to replace it with an appropriate one. At least keep enough clearance to the PCB (don't cut the replacement's leads if you decide to use a common component).


It also feeds the +30V regulator. Measure the voltages at Q27's and Q11's emitters and report.


Best regards!
Click to expand...


I left the amp aside for a few days. Yesterday I turned on the amp and switched on the Distortion, strangely after about 10 to 30 secs the distortion kicks in and starts to function. I turned off the amp and about 10 minutes later, turned it on again. Turned on the distortion and the same happens, the distortion starts to function only after about 15 secs. Once it starts to function, then it works as normal. Why the delay in turning on, is it due to a capacitor or transistor leakage. Plese advice.

Thanks

Carlos
 
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