K3 cooling fan cycling

[Paul Kirley]

The fans that cool the K3's 100-watt amplifier are thermostatically controlled.
All thermostats have a temperature spread so that they do not cycle on and off
constantly; for example, a thermostat might be set to turn on a cooling fan at
38 and off at 35.

I would like to suggest that consideration be given to expanding the K3's spread
between turn-on and turn-off temperatures to reduce fan cycling.  This might be
accomplished by allowing the operator to choose from a range of spreads (say, 1
degree to 5 degrees) in the Configuration menu.  

Presumably, the spread would adjust the turn-on temperature upward rather than
adjusting the turn-off temperature downward, as the turn-off temperature should
not be less than the ambient temperature.

Those who are bothered by fan cycling could then choose a larger spread to reduce
the problem.

73, Paul W8TM

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[Guy, K2AV]

The fan speeds are designed to minimize heat-related stress to the
transistors.  Personally I like not having to worry whether I have
toasted my final transistors because I may have inadvertently changed
some option for "designer" fan noise levels.

Transmitting transistors are finicky, do NOT tolerate heat well, which
is why Wayne & Co. have gone so oversize on the cooling fins. They
also have a calculated heat transfer function in mind.

If cycling bothers you try setting CONFIG:KPA3 to FAN1 or FAN2.  If
you are operating SSB, that may remove most cycling.  This adjustment
sets the MINIMUM fan speed.  "NOR" is fan off until called for.

73, Guy.

On Wed, Apr 13, 2011 at 10:48 AM, Paul Kirley <[hidden email]> wrote:

> The fans that cool the K3's 100-watt amplifier are thermostatically controlled.
> All thermostats have a temperature spread so that they do not cycle on and off
> constantly; for example, a thermostat might be set to turn on a cooling fan at
> 38 and off at 35.
>
> I would like to suggest that consideration be given to expanding the K3's spread
> between turn-on and turn-off temperatures to reduce fan cycling.  This might be
> accomplished by allowing the operator to choose from a range of spreads (say, 1
> degree to 5 degrees) in the Configuration menu.
>
> Presumably, the spread would adjust the turn-on temperature upward rather than
> adjusting the turn-off temperature downward, as the turn-off temperature should
> not be less than the ambient temperature.
>
> Those who are bothered by fan cycling could then choose a larger spread to reduce
> the problem.
>
> 73, Paul W8TM
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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