[mikethedruid]

If you are serious that "tubes don't seem to mind which direction they go into the socket," then you have a problem. All tubes are keyed in some way. In old types they either had 2 larger pins that allowed the tube to be inserted only in the correct way, or they had a peculiar pin layout that also only allows one way. Later types, octal and locktal have a thick post in the center of the base with a ridge down one side of it. This keys into a little cut out on the side of the center hole in the socket that the post fits into. Later 7 and 9 pin miniature tubes have a wide gap between two of the pins, which matches a gap in the holes in the socket, so they can only go in one way. If your tubes can go into the socket in more than the correct way, then you have a problem. Perhaps it is a damaged socket from someone forcing a tube in the wrong way. In that case you will have to replace the socket.