Hi, Tele lovers! I have read more than 10 posts about hum and buzz and had try to target the problem myself. But somehow I failed. I will explain it later. For a year or so, my amp would occasionally humming very and losing guitar signal at the same time during playing. Even turning the volume down is doing nothing. A trick that used to work is to switch the amp off and switch-on again. Now the trick fails, too. I have change all 7 tube on the amp...no good. Two more things to mention: 1. when the problem happens, the blue glowing of output tube will become brighter and easier to see. 2. I found that I can re-create or ease the problem by attaching or detaching ground wire. Let's say, it is humming now, and I can attach the amp chassis to TV cable's outer ring (which is grounded) to change the loudness of humming. But I can't control to make it louder or quieter. It is random. oh yeah, wall plugs in Taiwan are never grounded and the only undoubtedly grounded wire is the the TV cables. So, lemme tellya why I fail to target the problem: I found the parts list and the PCB layout: https://www.bruynooghe.fr/public/ampli/Schematics_Fender_amp/Vibroverb/63_RI_20Vibroverb.pdf However, I find that my board looks different in several places. For instance, the diodes are different and the Cap38 (C38) is not on the layout, let alone the definition of the file is not very good...I was very confused so decided not to do anything until the great Tele lovers show me the way!