Help! My trusty 8008 has failed! I think this was because the flight case it was in was loaded upside down into the van and it has rattled about a bit causing something to break... When it is powered on one of two things happen: (1) there is a loudish hum from both channels regardless of where the level controls are set. OR (2) there is a deep thud on power up, after which the hum returns as (1). If the unit is tapped it crackles and on one occasion the hum stopped but the process of plugging in a cable caused it to start humming again. I have previously repaired this unit by replacing all of the output transistors this was done circa 2004. However I do not think this issue is related. My thinking is as the hum affects both channels and is not affected by the levels controls, it must be a fault that is common to both amp stages possibly a fault on the power supply, maybe the rectification is wonky or a smoothing cap has failed. Apprecaite any thoughts from anyone who has experice of these amps! Not sure if I am being dumb but looking at the schematic (that I have) it does not show where the TL072 op amp at the input is deriving it's power, I'm assuming this is also on the +/- 15V rails but prefer not to assume! I will try and get it open today and have a look, but I do not have a test speaker in my workshop to test it so will have to test with a scope and signal gen.