[Collins] KWM-2A Internal Fans

[Howard Weeks]

We ran many pieces of Collins S-Line equipment for all kinds of purposes 
(SSB, CW, and RTTY) in the Army. Sometimes, it was setting on a table. 
In many cases, it would be mounted in some type of cabinet enclosure.

We didn't modify the radios but we did make sure that they had plenty of 
ventilation room around them if on a table. If on a table in a small 
closed space, we put fans in the room to circulate the cooling air. If 
the radios were mounted in some type of closed cabinet/console, we put 
big fans in the cabinets to move lots of air around the radios.

Our fans usually had filters on the air input side that had to be 
serviced periodically depending on the environment. If serviced 
properly, the inside of the cabinets remained reasonably clean.

They worked fine in that environment but that was during the 60's and 
70's when the radios were much newer than they are now.

I have several pieces that I have had for 40 plus years and have never 
felt the need to put fans in them.

Howard K5JCP

On 2/25/2015 9:19 PM, Dr. Gerald N. Johnson wrote:
> 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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