[Elecraft] K2 I/O Module Help Needed

[Don Wilhelm]

Mark,

I would bet you are using an externally mounted KPA100/KAT100 
combination.  That puts a load on the 12CTRL line coming out of the K2, 
and yes oft times L1 on the AUX board is overloaded and goes up in 
smoke.  It is usually OK with the KPA100 or the KAT100 alone, but the 
combination of the two overloads that tiny inductor.

You need to replace the inductor with one having a heavier current 
rating.  A toroid will do just fine.  If you have one of those tiny 
cores like used in the KSB2 RFC1 and RFC2, then just wind about 15 turns 
on that core.  Lacking that, use an FT37-43 core and wind about 12 turns 
on it (the FT-37 core is a bit large and untidy when mounted on the AUX 
board, but it works).  The inductance is not critical.  In fact, you 
probably can temporarily substitute a wire, but there may be noise 
coupling between your KPA100 and KAT100 at times, so I would not 
recommend the wire as a permanent fix, but it can get you going until 
you can get a suitable inductor.

If you want a tool to figure the number of turns needed on a core to 
produce a given inductance, I suggest you download miniRing Core 
Calculator by DL5SWB - it is freeware for radio amateurs - see 
www.dl5swb.de to download it.

73,
Don W3FPR

Mark Adams, PE wrote:
> Hi Gang,
>
> On FD, my K2 I/O board went south. It just stopped working when contest time arrived Saturday. Bummer. I've just dug into the radio and found that I have no power to U1 or Q1 on the I/O board and that L1 on the Aux2 Board is busted. Has a hole in its side to be exact. So, my junk box has no 15uH inductors hiding anywhere. I have some inductors but no way to measure them.
>
> Anyone have any ideas? Is there a resistor I could sub to finish troubleshooting? Maybe a few turns of #18 tinned wire would do the trick? I cannot even find formulas to help me out. 
>
> Yes, I'll order a few from the big E Monday, but until then......
>
> 73,
> Mark K2QO
>
>