[TowerTalk] 3-500Z on its Side

[Chucks Laptop]

Anecdotally, I made the mistake while I was posted in Laos in 1969 - 
1971, of turning my SB220 on its side to trouble shoot a problem. I soon 
discovered that wasn't a good idea. I noticed something wrong very 
quickly and shut it off, fortunately before damage to the filament 
transformer windings. Both tubes were damaged by the sagging filament 
syndrome. It's one thing to be offshore and quite another to be in 
CONUS. No internet, e-mail, just snail mail, or Amateur Radio. APO 
Services were there, but took lots of time.

I fired up my spare SB-200 and was back on the air. Several of the US 
Hams offered to send me the tubes, but in the end I got them from Henry 
Radio. I didn't know about the caveat of running the 3-500 tubes while 
on their sides. When the replacement tubes arrived, and were installed, 
the SB-220 fired up and worked. I got lucky. The bias circuit survived 
despite my best efforts to destroy it. It was pure luck that I didn't 
repeat the same mistake. I still didn't know that operating the tubes on 
their sides was a no-no. As I recall, there was nothing in the Heathkit 
Manual that mentioned this.  Perhaps Eimac had a bulletin, but being out 
of the US made some resources unavailable.

That complete station followed me to the Ivory Coast and operated 
without further problems. Great old amplifier, and remarkably, still is 
in many stations!

73

Chuck, W6AJW