[Elecraft] K2: Flaky 160M switching

[Don Wilhelm]

Jim,

Replacing K8 is not going to do anything for 160 meters.  The relay that 
switches in the 160 meter low pass filter is K1 on the K160RX board.

Try this the next time it happens - while on 160 meters, change the 
antenna to the RX ANT jack and set the RX ANT menu parameter to ON.  See 
if you obtain receive.  The RX ANT bypasses the Low Pass Filter.

You may have a poor solder connection on the K160RX board or its header.

73,
Don W3FPR

On 3/2/2019 3:28 PM, Jim KO5V wrote:
> 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?