Hi, I’m on my 2nd 500C restoration using a Metalbone kit. Before I began parts replacement, the set played—both R & L sides had excellent audio on original components. After each segment of cap replacement, I tested the set. Doesn’t appear I made any mistakes When I was all done, set sounded real good. Next step was replacement of C92, C98 & C91 can/electrolytic caps—in that order—caps from Hayseed. Each time I replaced a cap, I tested audio & everything seemed fine—except—after I was done with C91. When I turned the set on I heard a “pop” & saw a flash—happened so fast—couldn’t tell where it came from. Immediately turned set off. Didn't smell anything burned. Looked carefully for failed resistor—but found nothing. Later powered set up gradually with Variac & discovered that only the left side was playing--and playing normally. Everything else seemed normal (which told me the C91 hook up was OK). Using my Heathkit signal tracer, got good R & L audio both at volume control & at V15/12AX7. Got good audio at V12 (left phase inverter) 12AX7 but initially no audio at V13 (right phase inverter) 12AX7. Then again placed my signal tracer probe on the 1-6 (plate) connection of V13 & heard faint sound. At that very moment, smoke poured out of the right output transformer opening in the chassis & something smelled burnt. I Immediately turned set off. So, did I blow the OPT? And if so, what did I do wrong? Or, is there something else I should look for? And, how should I proceed? This probably gets old for you seasoned experts—but would appreciate any expertise any of you might bring to bear. Thanks. Learning the hard way, it would seem.