"Phil Allison" wrote in message
...

Gareth Magennis wrote:


Come on Phil, give us a clue, I'm stuck here.


** Most times I've seen such a problem, it was due to lack of shielding
between the output valve plate wiring and input signal wiring. Maybe a
shielded signal wire really isn't or the plate wires need to be twisted,
tidied and pushed against the chassis.

Everything in the JCM600 is crammed together making unwanted coupling more
likely.

Other times it has been due to high resistance grounds on pots or jacks -
or because some fool decided to put the OT next to the inputs jacks.


..... Phil





Yep, the plate wiring wasn't tidy or hard on the chassis, and one of the PCB
interconnects was way too close. (Some cable ties had not been replaced)

All is good now, thanks.


Gareth.