Harman Kardon AVR35 Hum

[pandaemonium9]

I have a Harman Kardon AVR35 with a hum thats causing distortion. I cleaned up the mains and made sure it was noise free (its a dedicated AC line in a conduit, nothing else is plugged into it), unplugged all the equipment from it to make sure I didn't have an externally caused ground loop. One of the 5 volt regulators runs a (little) hot because of the high input voltage, so I removed it and put in a DC-DC converter, replaced a couple of bad 100uF caps and it worked. A few months latter my sound was distorting again! I opened it up, poked around for a while, bypassed a ground loop I found, replaced those caps again (they where bad again), ran it and worked. A few months latter my sound was distorting again!! So I poked around in it again, everything looked clean, so I built a good mains EMI filter for it, cleaned up some suspicious wiring, replaced those caps again (they where bad again) and ran it. This made a huge difference! Its three days latter and my sound is distorting again!!!

I've heard a few people complaining about this problem with the AVR65 (almost the same circuit), does anyone have any ideas for me or should I beat it to death with the service manual?