REL Strata III - faint crackle/pop sounds


I've been very happy with my REL Strata III for many years. However, I recently started hearing a faint crackle/pop sound coming from it whenever it is powered on.

Any ideas for what I can try to do to diagnose the problem? Any recommended repair places? I can try Sumiko (USA distributor) but I would prefer a recommendation from folks on this forum before I send it to them.

Thanks in advance!
theasianmenace
Hooked it back up after a two week rest and it works fine, now. I have the contact cleaner and will use that if it starts acting up again. Thanks again for the suggestion.
I have a stentor III that is making scratching popping sounds. It even occurs when all inputs are disconnected and volume is turned all the way down. Rel informed me that the amplifier section is no longer available. Does anyone out there have any advice for me or does anyone have or know of a place I can purchase this amp. Thanks in advance for any help anyone can give me. Tom