[Elecraft] Vol 115, Issue 17 Power supply death and K3

[Pfizenmayer]

I had a very similar thing happen during a RTTY transmission on 20 M. - but 
I was using an ASTRON 35 which has foldback current limiting so no other 
damage took place. With no current limiting other things could fail.

What had happened in my case was a failure of the reverse polarity diode 
connected across the RCA DC jack which is there to protect against reverse 
spikes on that  jack. If this diode shorts then the "turnon" circuitry will 
not work either" . The 0.6 A protector fuse was still good and C220 was not 
shorted.

Check the DC resistance from the inner conductor of that RCA  jack to 
ground. If it is very low , that might be the problem. That diode is D35 on 
the K3 RF Board schematic. As someone else has suggested , trace thru the 
circuit from 12 v in thru the RFC and 6A F1 and D28 shunt diode etc .

73 Hank K7HP


> Message: 2
> Date: Sun, 10 Nov 2013 18:17:43 +0100
> From: Andrea Borgnino <a.borgnino at gmail.com>
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] Power supply death & K3 also any idea ?
>
> Hi,
> today i was in QSO in 17 meter band CW when my power supply (switching 
> from
> Nissei model MS 280A) has shut down (i was in tx with 100 watt). After i
> discover that the supply is death.. and also my K3 (#4777) now it's death
> also..connected to a battery it's not swithing ON... nothing...
>
> any idea ??
>
> thanks in advance and 73 de IW0HK Andrea
>