The Coleman lantern #4 chimney (NZ$5.20 in 1990) fits the 3 X 4-400
chassis that I was given by Barry ZL1DD - seems it was salvaged from a
Danish MF transmitter that ran 24/7/365 on 500kHz (stand-by most of the
time, of course).
The fan is 5 1/2" diameter, 3000 rpm from Aerex (France), configurable 3
phase, single phase - a serious fan. All three sockets show the same
problem - the filament connectors are discoloured, and the triangular clips
have been overheated so that they have lost temper. The sockets were
sub-mounted 1", so the through-socket pressure was modest. I get the
impression that the fan had been starved of air - maybe good routine
maintenance - regular change of dust filters might have helped.
However, the chimneys blew air past axial-finned anode connectors, and
the whole transmitter cabinet was exhausted by a larger fan system.
The new anode connectors that I an using are radial finned, and I would
expect to use either an axial fan, or even better an exhaust fan located
over the tank circuit that would drag air across the anode connector fins.
It's my guess - use chimneys with axial-finned anode connectors, and do
NOT use chimneys with radial-finned anode connectors. I'll still use an
exhaust fan with either set-up. My shack is a converted refrigerated
shipping container, so the exhaust fan is pre-installed.
My favourite rig is my Elecraft K2, so the shack stays cool.
Until I complete the rack of single-band 4-400 amplifiers.
73 Ken ZL1AIH
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