[Elecraft] OT: fan control in MFJ-4225MV switching P/S

[Nick-WA5BDU]

This could almost be "on topic", as the desire to control the fan in my 
MFJ-4225MV P/S is associated with my acquisition of a K3.  There was 
recently a discussion of switching power supplies for the K3 on the 
list.  I thought the MFJ unit was quiet while others found it to be 
noisy.  After the noisy fans in my FT-1000 and in my old PC left the 
shack, the MFJ P/S did become the loudest box in the vicinity. 

I had a sense that the P/S didn't really need that continuous fan 
activity, especially during low duty cycle operation or just listening.  
So I put a temperature sensor on a heat sink and use it to turn the fan 
on and off via a comparator circuit and MOSFET switch.  I think it's 
going to work out pretty well.  Of course, the simple circuit could be 
used on any P/S that runs the fan all the time but doesn't really need to.

Schematic and lots of rambling chatter about the little project are here --

http://pages.suddenlink.net/wa5bdu/fan_control_page.html

73-- Nick, WA5BDU
in Arkansas
#1195