[Elecraft] Re: K-1 TR Abnormality

[Brian Kassel]

Mike and Elecraft Gang:

    Yep, you are correct.  RF-C49 *WAS* indeed shorted! The K-1 is now 
back in perfect operating  condition.  After having read your message, 
and looking at the K-1 RF board schematic, your analyses was obvious. 
That light just never lit up for me when I was viewing the schematic.  
Great troubleshooting, Mike.  I replaced  RF-C49 with a .01 at 250 Volts 
that I had in my stock. I  looked at the parts list, and RF-C49 is not 
rated for voltage, so I assumed that it was probably 100V or less. I'll 
probably never really need the extra working voltage, but there was 
plenty of board space for the new, slightly larger unit so I used it.  I 
did also check  RF-C52, but it was OK.    So, if anyone experiences a 
K-1 failure due to a static discharge at the antenna, they might check 
both  Q-7 on the RF board, as well as RF-C49.  Q-7 is a bit of an odd 
part, so  probably the best source would be Elecraft Parts. Of course, 
there are other parts that may be effected, but this is what fixed  my 
unit.
  Once again, this list is really an amazing resource!

YMMV
Thanks Again,
Brian K7RE

Morrow, Michael A. wrote:

>Brian Kassel wrote:
>
>  
>
>>A while back my K-1 took a high voltage hit through the antenna
>>connector...I noticed a strange thing: whenever I connected an
>>antenna that had a DC sort at the feed point of the antenna,
>>like in a BETA match, the RX goes dead!...I am guessing that the
>>problem is in one of the 1N4007 diodes in the TR circuit that is
>>biased on when in RX...
>>    
>>
>
>Brian,
>
>It seems to me that if RF board coupling capacitor RF-C49 (0.01 uF)
>is *not* shorted, nothing you do at the antenna terminal should
>have any effect on the TR switching diodes.
>
>So, I suggest checking RF-C49 first.  I'd bet it has a pretty low
>rated working voltage anyway, so it is a likely failure.  You might
>want to check C52 too to see if it got hurt, though that would not
>have anything to do with your reported problem.
>
>73,
>Mike / KK5F
>
>  
>