572B possible problem

[WB4GUD]

70973I recently bought three used 572Bs from a friend and one of them is different from the others. It's a little hard to describe, but there are two pieces of U-shaped metal near the top of the plate. Five of the six are horizontal and the sixth is at a 45 degree angle. It isn't loose, but I'm not sure what the purpose of these pieces of metal are.

The question is, is this tube safe to use? I haven't powered the amp up yet.



73,
Howard
WB4GUD

[WB4GUD]

Thanks, I'll get the fire extinguisher out and fire it up. The two other tubes look "normal". I can't figure out what the metal piece does, possibly a shield of some kind on the filament. I paid $85 for three and the ham will take them back if this one doesn't work. I've found another 572B, so I'm set.

[KM1H]

I wouldnt say Chinese 572B's are any worse than the old US ones. The problem is the lack of a stringent quality control that lets the bad ones thru. US production had plenty of bad tubes, they didnt get out the door however.