just wondering if a pair of 2sa1492/2sc3856 would be a suitable replacement for the original 2sa1294/2sc3263 power transistors in a silver face fender frontman 212r?
Should be. Your sub is only 180v instead of 230v, but with 42v rails, the FM212R shouldn't stress them. Otherwise the specs look similar.
I've replaced both power transistors, drivers, mains and LV electrolytics and the LV and rectifier diodes but when I turn the amp on I get this hum almost like earth. Channel switching works, if I plug a guitar into it I do get signal but very dirty even though there is volume which leads me to believe that it's not power transistor related. I have checked the voltages all seems correct. So it could be power transformer problem or something in preamp rail. I noticed that the 2 led diodes D5 and D6 don't light up at all. Just wondering if anyone had any ideas because this one has left me stumped. Also what sort of replacement would I need for those 2 led's?
sounds like there is a lot of DC current flowing. did you turn the bias pot intothe direction of zero current ?
Check your power supplies, is there huge ripple on one or more? A failed main filter cap or just cracked solder to one will do that.
I call the way that amp is constructed a wedge chassis". It is narrow at front adn wide in read, so wedge shaped. MAny Fender solid state amps were made that way. I find inmany of them, the large filter caps vibrate enough to crack their solder.
I call the way that amp is constructed a wedge chassis". It is narrow at front adn wide in read, so wedge shaped. MAny Fender solid state amps were made that way. I find inmany of them, the large filter caps vibrate enough to crack their solder.