Fender red-knob "85" Cracks up.

[phfobric]

Super little amp. One trip to the shop for cosmetic work. This time, after swapping out a matching (ohms) specs 12' speaker with a speaker with a bigger magnet, some long weeks after some suprising crank coming form this "mini", a crackling ensued, in both clean AND gain channels. And then deafening silence.

Where should I start looking? Savy with a meter and other "knowledgeable closet techs' in the wings...

Thank you in advance for however you may guide us!

[pdf64]

It's likely to be dry joints on the power supply resistors on the main PCB. There was a great website which detailed this issue, but it's gone now.
Basically the big, square section ceramic resistors that supply voltage to the pre-amp run very hot. This weakens their solder joints over time.
Get the PCB out and re-flow the solder joints. Even better, replace those resistors with higher power types which will run cooler.