[Elecraft] K2 Q11 Repeated Failure

[Dale Putnam]

From: daleputnam at hotmail.com
To: alan7114p at whidbey.com
Subject: RE: [Elecraft] K2 Q11 Repeated Failure
Date: Sat, 10 Aug 2013 12:28:44 -0600




Hi Alan, That is the scenerio for the description of a static induced failure. And the reading is Q13. You didn't mention the ser. number, but it seems a K2PAKIT would be in order, to replace all of the stressed parts. Q11 and 13 become martyrs in order to save the rest of the radio, but the other components, Q5 and 6, have been stressed, and will likely fail in the future. In this case, Q13 was damaged, and Q11 took the hit.   It's been said, that this is the season, for the static hits. (I didn't hear it either).

Have a great day, 
 
 
--...   ...--
Dale - WC7S in Wy
 
 


> From: alan7114p at whidbey.com
> To: Elecraft at mailman.qth.net
> Date: Sat, 10 Aug 2013 10:35:57 -0700
> Subject: [Elecraft] K2 Q11 Repeated Failure
> 
> I have searched the archives in vain for an answer (might just be my
> limited knowledge, however).  My K2, which had been operating
> properly as a basic 10W, CW only with only the 160/RX antenna option
> installed, suddenly began having virtually no output on transmit. 
> When I opened it up, I found that Q11 was completely split in half.
> 
> After checking everything I could, I replaced Q11 and Q12 (this was a
> long, involved process).  I checked Q7 & Q8 for shorts to ground and
> found them to be OK.  I applied power but did not turn on the
> radio.  OK so far.  When I turned on the K2, Q11 immediately began
> to smoke and burst into flames within a half second.  I turned it
> off as quickly as I could.
> 
> When I checked Q11 and Q12 for short to ground I found that all leads
> of both transistors were shorted to ground.  I removed the devices
> and checked the pads in the same way.   Now only the emitter of Q11
> showed short to ground, which is correct.
> 
> I checked Q6, Q7 and Q8 for shorts to ground.  Emitters of Q7 and Q8
> show short to ground which is correct.  Q6 showed 1.5 ohms, which is
> also correct.
> 
> I also found that the resistance to ground from the emitter of Q13 to
> ground showed 756 ohms, even when I disconnected R63 from the junction
> of R60 and R62.  I expected to see about 2.8K ohms.  From what I can
> find on the schematic, there should be no other path to ground, but
> I'm not sure about this.  I don't know if I should be looking for a
> short or looking elsewhere.
> 
> Can anyone advise if this last measurement is correct?  Where should
> I look for the overall problem if this last resistance is not the
> problem.
> 
> Thanks and 73
> Alan K6ZY
> 
> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html