Workingman's 15 blew a fuse when turned on. (help me troubleshoot?)

[Stratapastor]

I've not adjusted the bias in any way... in fact. all i've really done once everything is said and done is replace a transistor that I broke and re solder the wires from the control board to the main board. At low volume it sounds ok... just very low. but if the volume is weak. i'm wondering if I don't have a bad solder joint somewhere. I'm still not an expert at soldering and user error seems like the most likely cause. I'll get out the tester and see what I can discover tomorrow. Right now I need some tylenol and a pillow.