static noise

im hoping someone out there is a tech and my have some insite on a problem i have..
my perreaux r200i started to develop a static hum in the left channel (with no input just power supply and speakers connected..changing power supply and power points,location house etc didnt help..so sent it back to perreaux where they tested heard the problem..but then it went away so they replaced some components just in case (what they thought would have been causing the problem) bench tested ok then sent it back..after a day or so i can hear the noise again not as loud as it was before but still there...
now what i have noticed is the channel with the noise is about 7deg hotter than the chan without the noise at the heatsinks... also the transformer on that side is quite audiable even in standby mode (has dual mono)
any suggestions?