I've got a customers Rev G in for some new tubes and a bias mod and I freaked out when I plugged it in and saw the bias light was on without the power switch being on! My current limited didn't go off and there wasn't any magic smoke, so I powered it down and opened it up. To my shock I saw an extra power transformer! A little baby one tied across the mains directly with a tapped secondary with only half of it used. It's got a fuse in line with it but still it's odd it's not on the switch as well. Followed the leads and it goes straight to D9, with the resistor missing from just before it. This transformer is providing the low voltage for the lights/switching circuits. The 50v tap is still there and providing the bias, but it's only supplying the bias voltage. The transformer is outputting about 12v RMS and the voltages seem to check out on the board.
Anyone come across this type of mod before? Can't say I've seen it before on any of the Mesas I've worked on/owned.
Anyone come across this type of mod before? Can't say I've seen it before on any of the Mesas I've worked on/owned.
