[Amps] Blown glitch resistor..twice

[SECOPSYS at aol.com]

Hi all...pair of 3-500  (LK-500ZC)....not running heavy...transmitting and 
the bullwhip bang that makes you jump...one glitch (series at each plate) 
resistor blew...replaced resistor...happened again several days later...  same 
tube glitch resistor.  Replaced both tubes with pair of older not full 
output (700 watts out on 80 mtr) 3-500s.  Problem gone.  I think I an assume 
that the bad tube is the one where the glitch resistor has twice blown.  Want 
to scrape one tube...but not the wrong tube!  Your thoughts would be appreciat
ed.
Many thanks,
Richard