Roland cube 60

[Buffalo Sam]

Trying to troubleshoot a hardly used cube 60 from the '70's.   Seems to have distortion or maybe reverb that won't shut off.  Speaker looks perfect and brand new.  No obvious burn marks or failures on the board.  Sprayed all the controls with cleaner and it's maybe a LITTLE better. I'll try it again tomorrow with some different guitar pickups[acoustic] and preamps and see if it's still acting up.  Any suggestions?

[Roly]

Roland Cube 60 schematic, thanks to;
http://www.freeinfosociety.com/electronics/schemview.php?id=1327

- check both supply fuses F1 and F2, 5 amp

- check the no-signal DC voltage across the loudspeaker

- check the supply voltages.  You should have +/-48V on the output stage and +38V feeding the preamp.

- turning the reverb control to zero should have the same effect as turning the reverb footswitch off

- try a known good lead between Pre Out and Main In

- try headphones

- try feeding the Roland Pre Out to the Main In on a different amp

- try feeding the Pre Out of a different amp to the Main In on the Roland (alternatively feed in the output from an MP3 player o.n.o.)

- try it with an external speaker

Post results.