Roland Cube 60 - Terrible Buzz

[itLEAKED]

Hello there, my first post... unfortunately it starts a problem, luckily its on this message board.
Thank you in advance to any and all help provided!

Roland Cube 60 COSM
Amp only: Terrible Buzz/Hum coming out of the speaker.
Input jack: nothing plugged in. When there is.. it doesn't make a difference
Pots themselves have no affect, Channel selection, FX, EQ, Volume... COSM


Trying to figure out what is the best way to go about attacking this issue

Thank you

[52 Bill]

The problem that you describe is usually one of two things, a short in the power amp or a power supply fault.

When you turn on the amp does the speaker push or pull in or out and stay there? If it does, then there is a dc voltage on the output and you should disconnect the speaker before going any further.

If there is no dc on the output, then I'd look to see if the main filter caps in the power supply have come unsoldered or gone bad.

[itLEAKED]

Speaker Response

the speaker is pulling in and staying in that position... so i disconnect the speaker.... what other steps should i take to diagnose or fix this issue? is it fixable?

[Jazz P Bass]

If the speaker is indeed "pulling in & staying in", then that indicates a compromised output section.
Check the output transistors for shorts.
Also the driver transistors.
It is good practice to test all of the resistors in the output section, too.

[soundguruman]

I think the output devices are shorted.

[itLEAKED]

Thanks so much for your replies guys....

[danmagruder]

are the Pots pushed in?

I see a lot of those amps that have taken a hit on the pots. The pots are built in such a way that the stem and threaded portion can pull away from the resistive material. If you pull the control board the pots can be put back together and away you go. Usually. this is a good place to start for all the cube series ampl. i work for the U.S. Navy Music program and we have probably 40 + of these that go on and off a cube truck. if they take a hit at least a few of those pots come apart.

Good luck