I sold an NOS type 42 tube that I had tested good with two tube testers and it even passed the gas test on my TV-7. When he plugged it into his rig it glowed and so he sent the tube back and I refunded his cost. I suppose it could be that my gas test was not working but I don't know how to check that. Any suggestions or advice will be appreciated.

What did you mean by, "it glowed", did the plate glow red? Was it a purple glow or a blue cloud? Red plate means to much current, problem with his radio, purple glow is ok on a power tube, normal. Blue cloud between the elements means gas, not good.
Greg

:I sold an NOS type 42 tube that I had tested good with two tube testers and it even passed the gas test on my TV-7. When he plugged it into his rig it glowed and so he sent the tube back and I refunded his cost. I suppose it could be that my gas test was not working but I don't know how to check that. Any suggestions or advice will be appreciated.