So I'm working on a 1982 Mesa Son Of Boogie, the one with two 6L6GC's. Classic story: it powers up on stand-by just fine, but when you switch it off stand-by, POP goes the fuse. I've switched out the power tubes (I have a tube tester and other amps... they are good tubes). No luck. I am using the correct fuse, 2.5A slo-blo... the power tube sockets are a little loose, but I stabilized them best I could and all pins are making good contact. The amp is NOT tube rectified. 4 little diodes look ok but haven't been tested (how would I?)... I'm running out of ideas. Oh, all the filter caps seem ok. None are shorted Hard to test them in circuit... but I took one out and it was dead on perfect. Even with the power tubes out, fuse blows when stand-by is switched off. Any ideas?