Noisy A100

[John Harris <john@skynet.co.uk>]

Hello All

This is my first contact, with a couple of problems that somebody might be
able to help with.
I have an early 1960's A100 hooked up to a Leslie 760. After the organ has
been running for approximately 2 hours, I get a noise that can only be
likened to sub bass feedback when the vibrato is switched on even with no
keys pressed which is present on both the Leslie and the internal speakers.
Removing the rear panel (just the frame/fabric cover and not the generator
cover) seems to stop it (I know it sounds stupid). I have read the FAQ and I
don't think that this is 'motorboating' more like 'supertankering'. I can
live without the rear cover but am concerned that it might be causing
damage. Any ideas?
Secondly, is it possible to remove the internal speakers, do I have to put a
dummy load on the amp? This is for reasons of weight as I would love to gig
with it and let the O1 and Wavestation do what they do best (not Hammond
impersonations).

Thanks in advance.

John H.