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

[NZ0T]

As I'm not a very technical person I just used a couple of resistors in
parallel to slow the fan down in my 4225.  I can't remember the values this
early in the morning but it seems to be working just fine.  The supply does
run a little warmer but not hot and the fan is no longer heard.

Bill NZ0T

Nick-WA5BDU wrote:
> 
> 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
> 
> 
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