[Drake] 3-500Z red by itself???

[Dave Edwards]

Several months ago, my Drake L75 had an issue where as soon as I 
transmit, the .5 ohm (or whatever it is) protection resistor would go POW.

I had another 3-500Z tube that has been sitting on a shelf for probably 
15 years!!  (condition unknown)

Tried it, and problem solved. Full output, no fireworks!

I tried the amp yesterday, full output, but after 5 minutes or so...even 
on receive...the grid current meter would go negative, and after a 
minute or so, the tube would slowly turn cherry-red, the fan goes to 
high speed.  So I shut it off.

Turn on again after several minutes...same scenario.

Time for a new tube from this century????

Thanks for your thoughts!

By the way...awful quiet list lately!

....Dave