I've read a number of posts about testing amp / power tubes and have gathered that the only way to test is in the amp the tube is used in . I have not had an amp that did this in my shack , but have heard and repaired some that did blow resistors and other components with bad / shorted tubes . So what I have done [ so far 811 & 572B ] is use my TV-7U/D tester for shorts before putting into amps for more testing . I've also read that you can put 1 tube in a 2 hole amp and test for output one at a time ? But I question if the imbalance with just one tube can be an issue ?