[Elecraft] K2: Flaky 160M switching

[Jim KO5V]

Thanks Don,

With the nut loose, it is much less intermittent. When it does hang up, a tap on the back of the left side panel
causes the 2Mhz birdie to return, so I think I'll order a replacement for K8 just in case it's been damaged.

With hands like catcher's mitts,"Beefing" fasteners is always an issue for me...

The 80M high current behavior I observed is exactly what you describe.

73, Jim KO5V  

-----Original Message-----
>From: Don Wilhelm <donwilh at embarqmail.com>
>Sent: Mar 2, 2019 1:04 PM
>To: Jim KO5V <ko5v at earthlink.net>, Elecraft List <elecraft at mailman.qth.net>
>Subject: Re: [Elecraft] K2: Flaky 160M switching
>
>Jim,
>
>Loosen the nut on the BNC connector or remove it entirely.  Since the 
>BNC jack is soldered to the board, the nut is only there for "pretty" 
>All will work fine without the nut.  The nut in any case should only be 
>a bit more than finger tight.  "Beefing" the nut up tight can damage the 
>BNC connector (same for the key jack).
>
>Yes, tightening the nut up tight is likely bending the RF Board.
>
>Check for the possibility that the rear panel is bent a bit in the 
>vicinity of the hole for the BNC jack.
>
>As for the high current on 80 meters after moving from a non-functioning 
>160 meters, that is not unusual.  The Drive to the RF Chain is maxed out 
>on 160 and when you move to 80, it will not be reset with a TUNE - 
>normal keying or speech will quickly correct it, but not TUNE until you 
>exit and re-enter TUNE.
>
>73,
>Don W3FPR
>
>On 3/2/2019 2:30 PM, Jim KO5V wrote:
>> After removing and replacing the heatsink panel to install an SMA connector for an IF-out port,
>> 160M is working intermittently. I think I have narrowed it down to a problem with the antenna's
>> BNC connector - It appears to be just slightly spaced away from the inside of the back panel,
>> so when its nut is tightened up, it must be flexing the RF board enough to affect K8. I've loosened
>> up the 2d connectors, to try and bring the connector/RF board into better alignment with the heatsink
>> panel, but every time I tighten up the BNC's nut, 160 eventually dies (I listen to the birdie at 2Mhz).
>> 
>> When I switch from a working 160M to 80M and then "tune", 80M gives a "hi-Current" error, and I
>> measure >20W on my external meter. A second "tune", and 80M is back to normal. Switching back to 160M,
>> I find the birdie gone (and no power out). Switching to 160M from a higher-frequency band usually finds 160M
>> working (but not always).
>> 
>> I have touched up the solder joints on all components involved with K8 and the BNC on the RF board, and all
>> of the joints on the 160M board.
>> 
>> So, I am going to place a shim between the BNC connector, and the heatsink panel and see what happens. Does
>> anyone have any other suggestions? I'm not sure K8 is bad, but maybe the BNC might be?