[Elecraft] [K2] Friends K2/100 problems?

[Don Wilhelm]

Curt,

The relays in the K2 and KPA100 are quite reliable unless they have been 
'bitten' by a soldering iron which damages the relay case.

Your report of - it failed and now it is working - is typical for an 
intermittent connection somewhere.  It could be bad soldering, but more 
likely it is a connector problem.

The T-R switching in the K2 and KPA100 is entirely electronic, so there 
are no relays involved in going between transmit and receive. There are 
relays to accomplish band switching and in the KPA100 2 relays will 
activate when changing the power between 10 watts and 11 watts.

The muting of the receiver is not controlled by relays - it is entirely 
electronic.
If you can hear any noise at all from the receiver with advanced AF Gain 
and fully clockwise RF Gain, the receiver is not muted, but there may be 
a fault in the receive path.

I would suspect a bad or broken connection somewhere.  First check the 
coax between the base K2 and the KPA100.  If the crimp pins are not 
properly seated in the connector housing, that is a potential source of 
the problem you describe.  There are locking tabs on the crimp pins - 
look at the rectangular holes in the housing - if the tabs are not 
locked in the holes, the crimp pins were not inserted correctly and new 
crimp pins may be required.

Make certain the KPA100 input coax shield is not broken.  There should 
be about 1/2 inch of flexible braid exposed.  Some builders do not strip 
the coax as instructed and have only a tiny bit of exposed shield while 
others will coat the exposed shield with solder.  Either condition is a 
recipe for a failed connection because the shield cannot flex.

You should physically remove the KPA100 and connect the antenna to the 
base K2 BNC jack.  If the problem goes away, the problem is in the 
KPA100, but if it persists, it is in the base K2.

73,
Don W3FPR


On 3/21/2014 8:49 PM, Curt wrote:
> Friend experienced the following with his K2/100.
>
> "Turned the K2 on, but I had no transmit, just the receiver being 
> muted but nothing else. I checked the mic on another radio and it was 
> fine, so somehow the K2 died while not being used, go figure."  Two 
> hours later...
>
> "I just got home and tried the cw mode, it worked fine. All the 
> controls seem to function ok as well, so another project for the 
> pile." One hour later:
>
> "Here's an update as of 4:05pm, it now works ok. I ran up to 20 
> meters, from the 40m where we were this morning, and tried the mic, it 
> was fine, so I went back to 40m, it then worked. I'm thinking a relay 
> was stuck, maybe, if so it will happen again."
>
> Any thoughts?  Are the relays in these radios prone to failure just 
> sitting?