[Collins] KWM-2A Internal Fans

[Dr. Gerald N. Johnson]

W5USI notes that some of the tubes die from heat. That they last longer 
with heat dissipating tube shields when those can be found and worked 
in. I'm sure the designers worked out that it could survive without a 
fan dragging in dirt and lint, but there's probably a note in the 
operator's manual about not running key down or RTTY for long periods of 
time at full power. I know from computer fans that the computer power 
supply and CPU need regular cleaning to remove the lint packed in by the 
fans. I'm sure tubes, especially PA tubes will last better with some 
cooling air, even better with cooling air if used for digital or RTTY 
modes. Also nearly every other component ages faster when hot, than if 
kept a little cooler. So a fan trades off cleaning maintenance for 
component replacement maintenance.

It would be good preventative maintenance to replace the two 68K 
resistors biasing the VOX relay tube cathode with 3 or 5 watt metal film 
or wire wound to lower the operating temperature of the resistor. Could 
be one 5, 8, or 10 watt 33K there. That resistor under the chassis won't 
gain much cooling from a fan cooling primarily the PA box.

I just thumbed through the index and first couple sections of W5USI's 
KWM-2 manual and I didn't gather he suggests a fan is a benefit.

The radio has run nearly 50 years without a fan, it will run more, but 
parts might last longer if fan cooled, if the lint buildup doesn't cause 
  other heating problems (and lint burns well, take your clothes dryer 
apart and get out the lint, I got a bucket full out of mine last month).

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 2/25/2015 7:47 PM, Gary H. Harmon, Jr. wrote:
> A good friend in Tulsa is asking me if a normal KWM-2A needs the fans that
> are sometimes sold for the radio.  They mount inside the radio and are
> powered from the NB socket.  Are they really needed in a normal operating
> environment?
>
>
>
> Thanks in advance.
>
>
>
> 73,
>
>
>
> Gary H. Harmon, Jr. - K5JWK - HAM Radio Archaeologist
>
> 6003 Archwood
>
> San Antonio, TX 78239-1504
>
> 210.657.1549h / 210.884.6926c/t
>
> gharmon (at) idworld.net
>
>
>
> Too many projects - Not enough time!
>
>
>
> "Retirement = Every day is a Saturday except Sunday"
>
> http://www.grissomroadcoc.org
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>
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