[Elecraft] Silent power supply for a K3s

[K9MA]

On 6/9/2019 23:16, Bert wrote:
> How would a switched PS take out a radio?
>
> Bert VE3NR 

Most likely due to overvoltage. Linear supplies are particularly 
susceptible, as the series pass transistor is under stress and can 
short. Switching supplies can fail if the voltage feedback loop somehow 
opens up. I've not heard of it happening, but all it would take would be 
one failed resistor or solder joint. I use a switching supply for my K3, 
but I built an external overvoltage protector. Of course, the supply has 
never failed.

BTW, I've found that the fan noise from the Samlex SEC-1235 is never 
audible above the K3 fans, except during long periods of receive, when 
the low speed supply fan is just barely audible. (I did the mod, so the 
supply fan runs at low speed all the time.) If I transmit long enough 
for the supply fan to switch to full speed, the K3 fans are already 
running fast enough to drown it out. Not to mention those in the KPA-1500.

I'm very happy with the Samlex supply. I've never detected a trace of 
RFI from it.

73,

Scott K9MA

-- 
Scott  K9MA

k9ma at sdellington.us