[Elecraft] Switched PS overvoltage

[Bert]

I haven't experienced that a switched PS causes overvoltage. They 
usually just die!

Bert VE3NR


On 6/10/2019 11:12 AM, K9MA wrote:
> 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
>