Thanks to all who shared their experience re. 3-500Z.
Running the amp upside down works for me.
Bert VE3NR
On 2020-10-09 14:43, Chucks Laptop wrote:
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
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