[AMPS] Re: CW amplifier tubes

[Martin Ellis]

Vic, K2VCO wrote:
>> One more question: may I get your opinions on cooling
>> 3-500Z's? Is it better to use chimneys and a pressurized
>> chassis, or the 'sb-220 method' with a muffin fan blowing
>> across the tubes?

 Carl KM1H replied:
> The 220 method works well as long as you direct some air
> at the socket pins.  The Harbach fan makes this an
> attractive ( cheap) option to chimneys.  You could also use a 
> muffin fan if you are careful in the selection and positioning.

The amplifier that seems to run cool and quiet is the KW TL922.
This uses a fan on the rear of the cabinet. It does not blow air
across the tubes.  The fan is mounted directly behind the
2x 3-500z tubes, and extracts air from the cabinet.  The cabinet
needs to be several inches from a wall to allow the heated air to disperse. 
After 2 days contesting on SSB, the top on the TL922
cabinet is still at room temperature.
In comparison,
the top cover of a 2KD-5 was hot enough to fry eggs.

Martin ZL1ANJ

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