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

[Don Wilhelm]

Fred,

That is great advice - "Fuse every lead".   "Whatever happens" is still 
good advice.
If there is any question about the power supply, I will first ask about 
it, then about the current being drawn.  So if you have something 
marginal, that will be revealed at the outset - proper connectors not 
withstanding.

"Pay attention" is by far and large the best advice.  It is the 
cautionary tale of old which advised us to keep the left hand in the 
pocket so high voltage paths would not have a direct path through the 
heart area of the body

So to me, "PayAttention" is more than an attention getter, it is a way 
of life that allows one to pay attention to all aspects of the 
situation.  In other words PAY ATTENTION - your life may depend on it. 
Voltage may kill. but current can maim - so consider both low voltage, 
high current sources as well as high voltage sources with equal respect 
- they are both are a source of power which deserves respect for safety..

73,
Don W3FPR

12/22/2011 10:48 PM, Fred Jensen wrote:
> In my case, Don is entirely correct, the ground occurred prior to the
> resettable fuse, and the only thing in the path was the trace from the
> power connector through D10 to the AUX 12V pin.  And, believe me, I will
> never "just check to see if it's all OK" again without a fused power
> lead.  It was a stupid mistake on my part, driven by haste ... and I'm
> not sure why, I know better.
>
> Rick has a good point however:  Someone mentioned The Ampere Theorem,
> "Any short circuit will eventually find a fuse."  A corollary is, "Make
> that bigger, it will find something else."  I escaped that this time,
> won't every time unless I pay attention.
>
> I think the bigger lesson for me is, "Pay attention to the details.
> This wouldn't have happened had I not plugged into the wrong connector,
> I *know* the right connector and have done it right many times, I just
> wasn't paying attention.  I still put one hand in my pocket, or sit on
> it, when poking in live gear even though 12V won't electrocute me.  Some
> old habits won't die.  Paying attention seems to have stuttered a bit on
> this one.
>
> Shorts on power leads, inside and outside the radio, can happen.
> Today's batteries have some incredible energy densities and can deliver
> huge currents.  They may not electrocute you but they can sure burn you
> and fry your radio.  Fuse every power lead.red K6DGW
> - Northern California Contest Club
> - CU in the 2012 Cal QSO Party 6-7 Oct 2012
> - www.cqp.org
>
> On 12/22/2011 5:09 PM, Don Wilhelm wrote:
>> Rick,
>>
>> It is not likely to "break something further down the chain" --
>> The K2 has a resettable fuse that will limit the fault current to 5
>> amperes or less.  The PC trace that was fried was before the resettable
>> fuse.
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