SEX, fixed level hum in 1 channel

[dvu969]

Hi,

Got a SEX amp for 5-6 years and have been using it pretty regulary either as preamp or powering tweeters.  It has always been dead quiet even on 98dB Lowthers.  Recently it developed a fixed hum in the right channel.  Swapped the tubes, but the hum remains in the right channel.  Not sure what's causing this.  Please advise.

Thanks,
Dinh

 

[Grainger49]

Swap inputs too, probably not the problem, then check the solder joints.  I have had a component that wasn't soldered at all, just crimped well, work for 2 years before biting my butt.