I ran multiple A and B lines 24/7 back in the 60s for autostart RTTY nodes.
The transmitters ran full power, approximately 125W output on 14.075
MHz, often with relay transmissions of 30 minutes or more key down.
Each transmitter had a small fan mounted on the back of the final cage,
blowing out of course. We didn't have the vast supply of computer fans
then, so these were 115 VAC fans, but were slower, almost silent in
operation. Even after a long transmission you could comfortably rest
your hand on the cabinet above the finals, which is very UN comfortable
in typical CW or SSB operation without a fan. It doesn't take a lot of
air, just a gentle breeze to push the hot air away from the cabinet.
Final tubes would last about two years, with "end of life" determined
when the output on 20M dropped to 100W. They were only $6 for a matched
pair, so it wasn't a big deal......
Incidentally, over a 5-7 year period, three stations, running 24/7, only
one failure occurred. A 12BY7 filament failed.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Don Cunningham wrote:
In my past, I used Drake twins on RTTY and ran two 115v fans in
series, one over the final compartment and one over the PTO area to
draw out the heat. They turn slowly, but fast enough to aid the
natural convection, and I never had any trouble with excess heat. Of
course, I was running the T4XB at about 50w out, not full bore, hi.
If you can find them, 230v fans on 115v will start and run slowly for
quietness too.
73,
Don, WB5HAK
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