[Elecraft] Help Please KIO2 L4 Burnt Out

[VK1OO]

Hi Guy,

Thanks

260mA!   Guess that would do it.
Exploring the power supply  etc now.

Mike

On 26-Apr-12 4:41 PM, Guy Olinger K2AV wrote:
> Do you have the DB9 plug that connects to the back of the KIO2 
> restricted to pins 2,3, 5 ONLY?  See page 21 in the KIO2 manual. If 
> you have hooked up a full RS232 to the KIO2 DB9 there is no telling 
> what has gone wrong, you can cause all kinds of problems.
>
> http://www.elecraft.com/manual/KIO2_man_rev_B.pdf
>
> Also L4 connects pin 5 of the common signal ground to the ground bus 
> in the KIO2.  If that goes through to a computer where a ground (black 
> 12V lead) has connected and your power supply to the K2 has a problem 
> in the ground (black) 12V supply wire to the K2 somewhere, and you 
> have other devices attached to the same power supply via common 
> grounding, including what is connected to the computer side of the USB 
> cable, the ground current attempting to flow via poor ground wire 
> connection will attempt to find any alternate route to the K2 any way 
> it can.  That ground fault will blow L4 in the KIO2 board.
>
> Take a DVM and see if you can draw current between pin 5 on the cable 
> and the ground of the K2.  If you can, you need to solve your power 
> supply problem.
>
> 73, Guy.
>
> On Thu, Apr 26, 2012 at 1:47 AM, VK1OO <mike.walkington at gmail.com 
> <mailto:mike.walkington at gmail.com>> wrote:
>
>     Hi,
>
>     My K2 rig control via a KIO2 stopped.  I discovered that RF sub
>     miniature choke L4, 100 micro Henry,  on the main KIO2 board was open
>     circuit - no evidence of excessive heat etc.  L4 is in the RS232
>     ground
>     path.  Shorting out L4 restored rig control.  I replaced L4 with a
>     larger version (all that I could find locally) but rig control didn't
>     work.  I tested the new L4 and it was open circuit, again no
>     evidence of
>     excessive heat.  So the question is, what would cause excessive
>     current
>     through L4?
>
>     I feed the KIO2 via a USB to RS232 converter which plugs into a four
>     port USB hub which plugs into a lap top.  This combination has
>     worked OK
>     for several years.
>
>     Mike VK1OO
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