[Amps] L4B hints wanted

[dave arruzza]

To all:
I recently acquired a nice L4B. It is fully operational with no apparent problems. 
 
Since the amp is a little old and components look original, I would just like some hints on what preventative maintenance I should perform before I have a failure. 
 
I look to the resident "gurus" for their advice. I read this reflector on a daily basis and the knowledge posted is considerable.
 
73
Dave W1CTN
"Radio Ansonia"