[Collins] KWM-2A Internal Fans

[Jbrannig at verizon.net]

I run low speed fans on top all my tube gear....why not....

Jim

-----Original Message----- 
From: Dr. Gerald N. Johnson
Sent: Wednesday, February 25, 2015 9:19 PM
To: collins at mailman.qth.net
Subject: Re: [Collins] KWM-2A Internal Fans

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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