Mihobro
Active member
One side of US power is essentially passive, while the hot leg can pick up all kinds of stuff, the UK two phase, both legs are pickup up the same junk 180 deg. out of phase to they should cancel.
The left cap IS showing the beginnings of leakage where the lead enters the capacitor body.Picture posted after I wrote. Caps show no sign of leaking, goo is just to hold them in place and limit any microphonics.
Zoomed in, still don't see it, brown colored stuff is the adhesive used to secure the component to the board, seen hundreds of amps like this. evidence of heat though as it should be clearer, not so brown. Not all cap failure will show as leakage of electrolyte though, only a real good cap meter can test. Also, these are 85 deg caps so I would generally like to see 105 or higher caps for power supplies. Problem is the best caps are radial packages, not axial. It is possible to shoehorn them in there. but it's not a pretty. Anyone got a preference for a manufacturer of axial caps?The left cap IS showing the beginnings of leakage where the lead enters the capacitor body.
This is what the infamous Fender Illinois Caps do.
Humbucking the power supply. Good idea what would it take to make this baby 240v it says on transformer replace with same type 250 volts?One side of US power is essentially passive, while the hot leg can pick up all kinds of stuff, the UK two phase, both legs are pickup up the same junk 180 deg. out of phase to they should cancel.
I guess in going down the list. Starting with speaker that's smart!Start by pulling all the tubes and checking all the power supplies. Because of the smoke, If they OK check out at the sockets too. It they are off then check bias resistors. then check for bad tubes, especially open circuit on the filament heater coil. (looks like some are AC,) If they check OK, then put in the preamp tubes and test the audio in to the insert out to check the preamp stages. If the preamps check OK then it is a problem in the power amp, Check the bias resistors 40 thru 55. Replace as needed. a burned bias resistor could be a sign of a shorted tube. So be prepared to replace output tubes as needed. The stage before the power tube, the dual triode, is called the splitter and divided the signal into two with one being the invert of the other, The power stage has two pairs of tubes. Be suspicious of the associated tube of a burned or open resistor. the tube could be shorted. If it all manages to power up without any smoking. If there is still no output it could be the output transformer. or the speaker, did I say to check that first? There are a few switches and relays in there. so all the loops and reverb send and return as well as feedback? could also cause the amp to. not pass signal.
from a guy with a Fender Tech Certificate (they were giving them away)
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