[Elecraft] K3 - ERR 12V - FIXED

[Ed K1EP]

I didn't have time to work on the radio until a couple of days 
ago.  When I first looked at the problem last weekend in the middle 
of the Elecraft QSO Party, I removed the top cover and the fan 
assembly.  I pulled on one of the wires that connect from the KPA3 to 
the circuit breaker and apparently the wire crimp was not great, as 
the wire pulled out.  I figured that was the problem and 
reattached/soldered the wire to the crimp connector, however this 
didn't solve the problem.  I was still measuring higher than normal 
resistances from the powerpole connector to the circuit 
breaker.  Checking the schematic, I determined that there wasn't 
anything in the path that should have resistance greater than a few 
milliohms.  I removed the rear bottom cover to get a better look at 
the power entry.  While continuously monitoring the resistance from 
the powerpole to the PA, I squeezed the motherboard-KPAIO3-KPA3 
"sandwich".  The resistance came back to normal!  I removed the 
single screw holding the KPAIO3 and again squeezed the 
combination.  12V is routed through two sets of multiple Berg stick 
type connectors from the main board up to the PA board.  Although I 
could not feel any movement, that is, the boards appeared to have 
been properly seated, the slight movement of the compression appears 
to have dramatically reduced the contact resistance.  All I can say 
is that there must have been some oxidation on the contacts and the 
slight movement eliminated it.  All appears to be well now, as I 
operated part of the Russian DX Contest this weekend with no loss of 
power or error messages.


At 3/15/2009 10:43 AM, Matt Zilmer wrote:
>I was 'inside' #24 anyway and saw this posting.  Measured the DC
>resistance across the CB.  I can't measure any resistance with the
>Fluke DVM.
>
>When keyed down on TUNE at 50W, I see no drop across the CB.  Sounds
>like the contact suface is corroded or contaminated on yours.  Better
>replace it.  At least that's easy to do, and Elecraft should help you
>out on this.
>
>73,
>matt W6NIA
>
>On Sun, 15 Mar 2009 09:36:47 -0400, you wrote:
>
> >All of a sudden this morning, I started getting an error message on
> >my K3, ERR 12V.  Then it scrolled Check Circuit Breaker, which I
> >assume was the PA circuit breaker.  The radio would not transmit
> >until power cycled and the power level was reset to below 12W.  I am
> >not convinced that it is a thermal issue, although it could be.  I
> >monitored the PA temp and it doesn't have a direct
> >correlation.  Temps are in the high 30's to low 40's.  I removed the
> >top cover and inspected the circuit breaker.  There seems to be
> >significant IR drop (10s of mv) across it even when not transmitting,
> >so I am wondering if maybe the circuit breaker is failing.  Has
> >anyone seen anything like this before?
> >