Hello, Being the proud owner of a Japan-built Squier Telecaster, I have been lurking this forum for quite a while. But the time has come to post at last about a problem I have been having for years. My amp is a Fender "Red Knob" Champ 12 and, since I play in a quieter environment than before, the 100Hz hum is driving me nuts. This amp was bought second-hand and has, as far as i know, always had this humming noise: -The humming is 100Hz and starts as soon as the 6L6GC power tube warms up -The hum is absent if the 6L6GC power tube is removed -The hum is steady with or without an input instrument and whatever are the values of the tone and volume and reverb control settings -The hum is steady with or without the 12AX7 preamp tubes -I have changed the four power caps to no avail -I have tried moving the wiring with a chopstick but the noise remains perfectly steady I am under the impression, given the poor quality of some of the solders on the power tube leads and on the output stage present on the circuit board that indelicate service was brought to this amp before I bought it. I am joining pictures and the amp schematic and would be grateful if someone could point me in the right direction.