K2 Q7 Blows Again

[David Heinsohn]

  I'm a bit frustrated!  Well actually more than a bit.  Q7 on my K2 has
blown again!  This is the third time it's blown.  In each case it's
blown after a period of normal operation.  This time the conditions were:

  1.  I'd had two PSK31 qso's earlier in the day.  At well over an hour
earlier.
  2.  I was tuning up and down the bands checking on the conditions on
various bands, esp. PSK
  3.  As I went from 15 to 12 meters I heard a loud snap.  The rig
continued to receive normally
  4.  Powered off and leaned over to check that the ground was still
properly attached.  It was.   BUT smelled that smell that we never like
to smell.  The magic smoke had gotten out of something.
  5.  Measured the ground from several places on the rig to the ground
connection as it leaves the house.  All showed less than 0.1 ohm.
Checked the security of the connection at the ground rod outside.  Seems
good.
  6.  Weather conditions at the time:  Blowing snow with temps about 20 F.
  7.  Tried to switch antennas and couldn't do it.
  8.  Checked the ATU indications on the menu display, the rig shows it
not available and won't allow reconnect.  (note the number two antenna
is the active antenna and goes to a switch, all indications are that
this is a working antenna.  Receives find on all bands.)
  9.  Disassembled the K2, no visual indications of problems until a
took the heat sink off.  (I hate taking that thing off!!!)  Q7 is in
pieces again.
10.  Called Elecraft.  Closed for the holidays!!!!  (That I expected and
find no fault.  BUT the Stew Perry Challenge starts in 48 hours and I
really don't want to use one of the other rigs for that!!!  @#$%^&*  )

 I suspect static build up on one of the antennas, esp. the 160 dipole
that is used for all but 80, 40 and 15 meters.  But I was not
experiencing unusual static on 20 only moments before.

    Now to decide whether I want to try the Icom, the Kenwood, or the
Yaesu for the Challenge.  None of them are even close to the K2s
receiver for cw.  And I'm going to be doing it as QRP too.

  Thanks for Listening.
  Don I suspect you'll be getting 6708 back next week.  :-(  Then again
I might just try installing those four transistors again myself.  I
really don't like desoldering stuff.

 de
KD0R
David

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[Don Wilhelm-4]

David,

I am sorry to hear that happened at such a bad time for you.
If you have just been replacing Q7 when it fails, then having it fail
again is quite likely.
Order the K2PAKIT from Elecraft and install all the transistors included
- Q7, Q8, Q11 and Q13.  It is common for a PA transistor fault to damage
Q11 or Q13 and if not replaced with the PA transistors, the bias will
not be correct - and can cause a subsequent failure of the PA.

73,
Don W3FPR

David Heinsohn wrote:
>   I'm a bit frustrated!  Well actually more than a bit.  Q7 on my K2 has
> blown again!  This is the third time it's blown.  In each case it's
> blown after a period of normal operation.  This time the conditions were:
>  
>  
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