K2 control board U3 'hot' question

[Will-69]

Greetings folks,

  Just got myself a K2 (yay!) as it sure makes for a very nice rig
and kit to build.

  I've just completed the control board, front panel and the minor
assembly on the RF board.  Upon power-up, there's NO smoke (yeah!) but...
I did notice that the area of the control board where U3 is located seemed
hot.  At first I thought this was attributed to the regulators directly
below it.  Instead, I'm now feeling (and I mean feeling!) that U3 is
pretty hot.  I managed to just run the DISPLAY test to fetch the voltage
and saw it show "E 17.8 i .68"

Now, I did test the power supply, and it's happily putting out 13.8V all
the way through the RF board.  But it looks like a simmering U3 and the
display are pointing to something wrong with the voltage and current
sensing circuitry.  Am I on the right track?

Thanks
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[dave.wilburn]

In my past experience, hot chips are usually in backwards.  Also look
for any bent pins or shorts.

David Wilburn
[hidden email]
K4DGW
K2 #5982


[hidden email] wrote:

>
> Greetings folks,
>
>     Just got myself a K2 (yay!) as it sure makes for a very nice rig and
> kit to build.
>
>     I've just completed the control board, front panel and the minor
> assembly on the RF board.  Upon power-up, there's NO smoke (yeah!) but...
> I did notice that the area of the control board where U3 is located
> seemed hot.  At first I thought this was attributed to the regulators
> directly below it.  Instead, I'm now feeling (and I mean feeling!) that
> U3 is pretty hot.  I managed to just run the DISPLAY test to fetch the
> voltage and saw it show "E 17.8 i .68"
>
> Now, I did test the power supply, and it's happily putting out 13.8V all
> the way through the RF board.  But it looks like a simmering U3 and the
> display are pointing to something wrong with the voltage and current
> sensing circuitry.  Am I on the right track?
>
> Thanks
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft   
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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[Will-69]

Hi all,
  Just wanted to say thanks for the feedback on this, problem
solved.  Checking under some pins at U3 revealed a short.  All is well
now, and it's on to building the RF board, Part I.

Thanks again,

Will

On Thu, 19 Jul 2007, [hidden email] wrote:

> Just got myself a K2 (yay!) as it sure makes for a very nice rig and
> kit to build.
>
> I've just completed the control board, front panel and the minor
> assembly on the RF board.  Upon power-up, there's NO smoke (yeah!) but...
> I did notice that the area of the control board where U3 is located seemed
> hot.  At first I thought this was attributed to the regulators directly below
> it.  Instead, I'm now feeling (and I mean feeling!) that U3 is pretty hot.  I
> managed to just run the DISPLAY test to fetch the voltage and saw it show "E
> 17.8 i .68"
>
> Now, I did test the power supply, and it's happily putting out 13.8V all the
> way through the RF board.  But it looks like a simmering U3 and the display
> are pointing to something wrong with the voltage and current sensing
> circuitry.  Am I on the right track?

_______________________________________________
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Post to: [hidden email]
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