Why did my amp just crash and burn ?

Your a lucky man, all is well. Be sure to match fuse exact, after this post I’m going to turn off my amp when switching interconnects or any other wire from now on OP you taught me a lesson.  I just ordered 10 fast blow ceramic fused from Mouser .62 cents each, if you need a place to source correct fuses. Conrad Johnson charges $7.95 per fuse at .62 might as well get a life time supply.

Amp took out a fuse last week on the output tube protection circuit. Had the old xf2 tubes tested there all good. Conrad Johnson said that is normal and keep using the old Mullard’s until it takes out fuses repeatedly. The tube did not red plate. That’s very confusing to me for him to say that, got to ask while I’m here anyone heard of this? 
 

Nice glad it all worked out. 

@chaseton Glad you found the fuse drawer and especially the fact that there was a spare present. Remember now to acquire another fuse to put into the “spare” slot for future use if needed. Again congratulations.

OP,

Happy to hear it worked out. I appreciate you sharing.

I don’t fiddle with the amp on… but I have been known to swap interconnects on other components. I am not very patient. Good reminder for me. While it is less likely to cause a problem on other component, Better safe than sorry.

Glad you got the amp working again. If an amp has to be opened up to replace B+ fuses be careful. Even with amp unplugged and off, the power supply capacitors can still store dangerous energy. Most power amps drain this energy. Saw a friend loose part of a screwdriver tip when it shorted a giant capacitor. It is also bad to rapidly cycle amps on off on. 

Weirdest thing I encountered was a friend tripping over a speaker wire. As expected it blew the amp fuse. It also blew the fuse in the Linn Sondek LP12 turntable. Took a while to find that.

Thanks,

aldnorab