[Elecraft] KPA3 misbehaving

[Russell Tobolic]

Steve;

I believe you have the same problem I had a few years ago on my K3 s/n 732.  It turns out that the current sensor IC, U6 on the KPAIO3 board was toast.  When you go above 12W this sensor measures the current to the KPA3.    There is also the same sensor (U1) on the RF board which is protected against reverse voltage on the 12V in.  The sensor on the KPAIO3 board is not protected against reverse voltage as this is connected directly to the input connector.  Please don't ask me how I found this out.   Could you have possibly reversed the 12V to the rig momentarily?  I replaced U6 and that fixed it.

Russ, N3CO


________________________________
 From: Steve Reed <ai7az at arrl.net>
To: Elecraft Discussion List <elecraft at mailman.qth.net> 
Sent: Sunday, May 6, 2012 3:55 PM
Subject: Re: [Elecraft] KPA3 misbehaving
 
OK, another update.

I tried the PA alignment procedure with the K3 utility.  The 5 watt
alignment goes fine.  The 50 watt alignment fails with "Hi Curr".

Removed the KPA3, checked for anything obviously loose (all looks good) and
reinstalled.  Same error....

Guess this will be a call to Elecraft tomorrow, unless someone in this
forum can help.

Steve, AI7AZ


On Sun, May 6, 2012 at 10:04 AM, Steve Reed <ai7az at arrl.net> wrote:

> All,
>
> Here's the latest on my K3, now that I'm back from 7QP and can put it up
> on the bench and focus on this.
>
> When the PA setting is set to "normal", I can in fact hear the relay click
> when I turn the power control past 12 watts.  However the display keeps
> indicating "Hi Curr" and kicks it all back to 12 watts or lower.  As you
> turn the power knob up, you can see the power setting increase, but "Hi
> Curr" keeps flashing in the display.  This is all *without* the K3
> transmitting.  Go into transmit mode and all you get is definitely 12 watts.
>
> The serial number is 5662.
>
> I plan on calling Elecraft about this tomorrow.  In the meantime, anyone
> have some ideas?
>
> Steve, AI7AZ
>
>
>
>
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