Roland cube 100 guitar amp- loss of power

[cubeman]

I need advice on procedure for replacing the power transistors on my trusty old orange cube 100 please.

[52 Bill]

If a loss of power is your problem, I doubt that replacing the output transistors will cure it. They don't really wear out like tubes do.

[deadorange]

Hi, I know its been a long time since your post but did you manage to find the answer? I have the same amp and I'm facing the same problem. I've sent it to two different places and none could fix it. I'm trying yet another roland authorized shop but they've had it for nearly a month and can't seem to solve the problem. They replaced CIs and are now replacing the output transistors (which was also my guess in the begining). I anyone else has any ideas I'd love to hear them.

[dsflores]

Does any one have a service manual for this superb old-school guitar amplifier? I manage to put a old cube-60 back to working condition lately. It was a power supply problem. I had to change capacitors in power supply section. Although the reverb tank was busted. It was in that condition when i got it.

Now i have a cube-100 with an odd problem. The normal channel volume level does not max out. Setting it at 10 will only make it sound like its on 2-3 even when the master volume is also maxed. The drive channel has no problem.

Any ideas? the service manual will be a very big help


Thanks in advance.

[52 Bill]

I don't have the manual, but in an amp this old, I'd check all of the electrolytic caps in the signal path. They will often go off value and cause signal loss.

[dsflores]

Hi Bill,

Thanks for the quick reply. I would check on those caps then. Lately i have been scouring the net for schematics.

[Jazz P Bass]

If the Cube 100 is anything like the Cube 60, then two points must be verified, if you have low output.
#1: The power amp in jack is a normally closed contact. If it gets cruddy, it will not pass full signal.
#2: The headphone out jack: same thing.

[Peter32]

This might help ...

Hi,

I exactly had the same problem (normal channel low, drive channel fine) and found the solution.
On the preamp board there are 4 transistors C1570 in the left-back corner (this is with the potentiometers in front).
The 2 on the left take care of switching the leds, the 2 other are switching the sound (normal to overdrive) when you pull the switch or use a pedal.
I switched the 2 transistors on the left by the 2 other and all the sound came back.
To my surprise, both the leds did work too, so I think it might just have been a wrong contact or a transistor on the edge.