[CQ-Contest] Advice about HF amplifiers

Jim Monahan K1PX at msn.com
Mon Sep 6 20:07:44 EDT 2004

Regarding the SB-220/SB-221, I also had the problem with the solder in
the filament pins melting.

I took the problem two more steps in addition to the fine recommendations
of others.

Since the filament pins are in line to the air flow, I found that the back pin was
far more likely to melt.

I spun the two 3-500Z's 90 degrees so that both filament pins are broadside to the 
air flow.

Then, I replaced the fan assembly with the replacement unit available from Harbach
Electronics which is now owned by W8CQ. This unit has about 50% more air flow and while
it is a bit louder than the original fan assembly, it keeps the tubes, and filament pins,
relatively cool. 

73, Jim, K1PX

K1PX at msn.com<mailto:K1PX at msn.com>

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