K2 resetting itself

[Chris Kantarjiev K6DBG]

I was happily monitoring 14.058 this afternoon when my K2 turned itself off.
I cycled the power button and it came on enough to say ELECrAFT and to
hear a little audio, and then shut down. Then cycling the switch didn't
do anything. Or would do a little.

I figured it was causing F1 to reset. Put it on the bench and sure enough,
it's drawing about 5.6A ... the manual is not terribly helpful about
diagnosing.

I opened it up and started removing boards. Can't really find anything.
It would have been too easy if something in the battery charging circuitry
had shorted ... With the switch "ON", +12V shows 105 ohms to ground.
That can't be good.

I'm not really sure how to diagnose this. The PA transistors seem
like a place to start: the emitters are grounded, when the switch
is OFF, the collectors have about 100 ohms to ground (can that be
right?) , the base about 134 ohms.

Suggestions would be quite welcome.

73 de chris K6DBG
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[w7aqk]

Chris and All,

I had a power on--power off problem some time back.  I think several others
had a similar issue.  My problem was traced to the I/O board.  I believe
this has been fixed, and later units don't have the problem.  Not sure what
your number is though.

I suggest you contact Gary or Rene at Elecraft.  They are pretty sharp, and
I bet they can get you fixed up quickly.

Dave W7AQK


----- Original Message -----
From: "Chris Kantarjiev" <[hidden email]>
To: <[hidden email]>
Sent: Monday, March 23, 2009 8:27 PM
Subject: [Elecraft] K2 resetting itself

>I was happily monitoring 14.058 this afternoon when my K2 turned itself
>off.
> I cycled the power button and it came on enough to say ELECrAFT and to
> hear a little audio, and then shut down. Then cycling the switch didn't
> do anything. Or would do a little.
>
> I figured it was causing F1 to reset. Put it on the bench and sure enough,
> it's drawing about 5.6A ... the manual is not terribly helpful about
> diagnosing.
>
> I opened it up and started removing boards. Can't really find anything.
> It would have been too easy if something in the battery charging circuitry
> had shorted ... With the switch "ON", +12V shows 105 ohms to ground.
> That can't be good.
>
> I'm not really sure how to diagnose this. The PA transistors seem
> like a place to start: the emitters are grounded, when the switch
> is OFF, the collectors have about 100 ohms to ground (can that be
> right?) , the base about 134 ohms.
>
> Suggestions would be quite welcome.
>
> 73 de chris K6DBG
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html 

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[Chris Kantarjiev K6DBG]

>
> I had a power on--power off problem some time back.  I think several others
> had a similar issue.  My problem was traced to the I/O board.

Thanks, Dave. Mine is serial 32xx - and the radio had been on for
several hours when this happened. I've had it on for 24 hours straight
during a contest. This is new, and quite odd, behaviour.

I haven't pulled the control board to isolate it yet, but that's next.
I *did* pull the heatsink and the shoulder washers were as they
should be (and the semi-short to ground is still there).

chris
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