fried Peavey 5150 Combo

[PFC_Camp]

Today while letting my amp warm up in standby it made a slight quiet pop then started stinking i noticed smoke. took it apart and on the board located by the Bass knob i found a small white box shaped thing next to what looks like a capacitor burnt and one of the posts it was connected to around it on the board looked a little charred wondering what the thing is that burned what it does what could have caused it and if it is fixable cost wise need some advise on this please thanks

[Jazz P Bass]

The 'small white box shaped thing ' is a cement power resistor.

The schematic designator is "R98". (directly below V3)
It is a 4000 ohm/ 5 watt resistor that feeds the preamp supply.

5150 R98.pdf

[PFC_Camp]

do they just go bad or did something i have hooked up cause it my set up is a mesa triple rec on right the fried 5150 on the left and a rocktron xpression used to run both in stereo rocktron is hooked up in effects loop of the Mesa right side and left side into low gain input of 5150 been using that way for couple days sounds absolutely amazing well did till today

[52 Bill]

Resistors can just go bad, but much more likely is that something in the circuit that it feeds is drawing too much current. That would cause that resistor to overheat and burn up.

So the resistor will need to be replaced once the cause of the problem is found and cured.

[Enzo]

Resistors can just go bad, however, they never burn up on their own, something else causes them to burn up.

[Jazz P Bass]

My vote would be on C56 going south.

From here, it's all guess work without a few voltage & current measurements.