Often when I buy or receive old tubes, pins on the tubes are oxidized. Big issue with oxidation is that it prevents pins making good contact with the socket. Because of that in the worst case, tube would appear to be completely dead or it will make strange noises during playback. Fixing this issue is quite simple. Just pray pins with DeoxIt D5, wipe in with a cloth and the problem will be solved in the majority of cases. If that don’t help, sometimes using a small screwdriver and cleaning pins one at a time to remove junk off the metal. They spray with Deoxit again to ensure that what ever is left is dissolved.

Another common problem, specially with old octal tubes, is that base is loose – you can feel that it twists against the glass envelope. That is very dangerous because a very expensive tube can die if base twists and disconnects internal wiring or even shorts. Solution is very simple, use a bit of transparent nail polish , go around the base and apply small amounts of the nail polish in the space between the base and the glass. Now let it dry and all is better – base is attached to the glass envelop again. Transparent nail polish is very hard to see, so the tube looks good.