I almost hate to say anything, but

We have this certain transmitter which has been on the same tube since June 6, 2001.  Come to think of it, the transmitter itself has been on the air for the same amount of time without failure.  A testament to its designer…

Broadcast Electronics FM20T, WYJB, Albany, New York
Broadcast Electronics FM20T, WYJB, Albany, New York

According to my calculations, that is 151,691 hours or 17 years 3 months and 22 days.  The tube is the original EMIAC 4CX15000A that came with the transmitter.

I am a little nervous about turning it off to clean the cabinet.

EIMAC 4CX15000A tetrode
EIMAC 4CX15000A tetrode

We have a spare on the shelf for the eventual replacement of this tube, but I really want to see how long this thing will last.  This is also one of the last tube transmitters we have in main service.  There are several backup tube transmitters still around.