Switched Tube Consequences?

[JHow]

Oh yikes! I was tweaking my home built 5C1 and had removed the tubes to work on the guts. When I put it back together I switched the 6SJ7 and the 6V6 in the sockets (despite my having labelled the sockets with a sharpie pen). Needless to say, when I fired it up, at first I got nothing, I jiggled the volume, got sparks and smoke out of the pot and quickly shut it down. I stared at the guts for bit tracing my recent mods, satisfied that looked good, I flipped it over and saw the reversed tubes. I flipped the tubes and, voila, everything seems to work - volume pot seems okay. What are the consequences of this mistake? If trouble develops down the road, where should I look? The big lesson is really don't work on circuits when you are tired, but this is my hobby and I have a day job; I only get to work amps late at night.

[Enzo]

If it works, it works, just watch the thing and don;t leave it running when you leave the room. SOme parts could be damaged, or not. if something was hurt, it should show up soon enough. Or it might be fine.

ANd if it ever craps out, don;t waste time looking for a list of what the failure is going to supposed to be, just fix whatever is wrong.

In the output tube socket, the 6SJ7 would turn into a diode between the volume control and B+, using its cathode and control grid. At high volume settings, the pot is 1M and would limit current. If you turned the pot down, then the series resistance that it is gets less and less so current through the tube would rise. That COULD have stressed the 6SJ7, or not. And at low volume setting, that COULD have damaged the pot, or not.

And at the 6V6 in the preamp socket, the cathode of the tube would have B+ on it. That would no doubt exceed the heater-cathode voltage limit, but it probably didn;t hurt anything.

[tubeswell]

You could measure the DC resistances across your pot to see if it is responding as predicted. A pot is inexpensive to replace. Otherwise watch for tube electrode arching or other smoke for a good while with it on and the back uncovered (as Enzo suggested). When you see smoke (or hear bad humming/crackling/bubbling/boiling) switch it off (at the wall) immediately and make a note of where the smoke was coming from.

[JHow]

Well it seems okay. I guess I got lucky. Played for a long time last night and no untoward smells, noises or heat. Thanks for the advice and explanation of what would happen with the tubes.