Fender Twin - Pin 3 Melted

[Blenji]

I'm currently restoring a Fender Twin. I recapped all the filters, put in new tube sockets, new screen and grid resistors, and new JJ 6L6's. On turning it on I noticed a flash in one of the tubes, and a moment later there was some smoke. After opening it for inspection I found that pin 3 (plate) on aforementioned tube's socket had badly burnt. No fuses popped. On removing the tube, there was solder melted to the pin and the plastic base had slightly burnt. Any idea's what may have caused this?

Thanks all.

[Enzo]

COuld be many things, but I'd first suspect an arc, and since you had just done all that changing, I'd also fist suspect it might have been caused by a little loose bead of solder or even a solder bridge. Or perhaps a bit of excess lead wire soldered to the adjacent pin 2 came too close. Are your 100 ohm resistors OK on the heater ground? Pin 2 - the heater - of the 6L6 is the most likely arc point for pin 3.

[Jazz P Bass]

And if all of that is not the culprit, you may have gotten a bad tube