[Elecraft] K2 - Fuses ...A Cautionary Tale

[david]

I took a Sharpie that had laying on my workbench, and "changed the
color" of the aux power connector both on the board and the wiring
harness, which is what the manual suggests, IIRC.  No, it doesn't
prevent one from swapping them, but is a visual indication which one
goes where.   One still has to take their time when working on a $1000
piece of equipment.  Glad you got it fixed and nothing else was smoked
besides the PC board trace.

73, David  
AJ4TF

> 
> Message: 7
> Date: Thu, 22 Dec 2011 12:08:43 -0800
> From: Fred Jensen <k6dgw at foothill.net>
> Subject: [Elecraft] K2 - Fuses ...A Cautionary Tale
> To: Elecraft Reflector <elecraft at mailman.qth.net>
> Message-ID: <4EF38E4B.9000603 at foothill.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> With a feeling of great stupidity coupled with a desire to prevent this 
> for others:
> 
> Yesterday, I reassembled my K2 [#4398, Sep 2004] with the QRP top and 
> KAT2, having just sold my KPA100.  I was interrupted by a phone call 
> after plugging the edge connector and speaker in.  When I returned, I 
> plugged the KAT2 coax into ... AUX 12V, grounding the 12V. :-(( 
> Finishing the assembly, I decided to quickly power it up just to make sure.
> 
> Now, the cables I normally use with the K2 and KX1 have in-line fuses, 
> and I have just converted all the DC in the shack to APP.  The power 
> supply was at the other end of the desk, so I grabbed the LiFePO4 15C 
> battery, plugged in one of my little adapter jumpers [APP to coaxial 
> power] ... no fuse ... and plugged it into the K2.  I heard a distinct 
> click, I wondered if the on/off switch was on, it wasn't, I turned it 
> on, and radio was dead.  At this point, I noticed the distinct odor of 
> misrouted electrons, an odor we all recognize, and removed the battery.
> 
> With no fuse, the heavy trace between the power connector and hot end of 
> C196, way above and beyond its call of duty, sacrificed itself. 
> Fortunately, the trace is now replaced by a short jumper wire and the 
> radio works.  D10 seems to have survived, probably because, when used as 
> a fuse, a PCB trace is ultra-fast.
> 
> A colleague of mine once said, "The problem with 'Lessons Learned' is 
> that they rarely are."  Thus encouraged, my lessons from this are:
> 
> 1.  Never connect any power to any radio without an in-line fuse.
> 
> 2.  Tape or otherwise cover AUX 12V unless you're actually using it [KPA100]
> 
> 3.  Just because you've done something many times does not mean you'll 
> get it right on the many+1'th time.  Many years ago in military uniform, 
> I knew this.  I guess I just forgot.
> 
> 73,
> 
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2012 Cal QSO Party 6-7 Oct 2012
> - www.cqp.org
> 
>