[Elecraft] K2 Troubleshooting help

[Michael Carter]

Hi Sam,

Go with Don's advice - he knows ALL the common and not-so-common problems with the K2.  He has repaired and built more K2 rigs than anyone in the Elecraft community!

If there is an intermittent short on the /DASH line into the MCU, it may be a free-floating bit of wire end lodged somewhere or a thermal flexure of a solder bridge.  As Don noted, the monolithic caps C1 and C2 are not the most likely source of leakage from the pulled-up /DASH and /DOT-PTT lines.   It may be worth checking their vicinity both topside and bottom-side of the RF board for other circuit faults. They are both located on the left edge of the RF board about midway back from the front edge (front panel facing you).

If there is a short on another input pin of the MCU, only careful visual inspection under a magnifier will reveal it.

73,
Mike, K8CN
________________________________
From: W3FPR <w3fpr111 at gmail.com>
Sent: Sunday, May 31, 2026 2:50 PM
To: Sam Smith <sam.smith at pnoft.com>; Michael Carter <Mike.Carter at unh.edu>
Cc: Elecraft Reflector Reflector <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] K2 Troubleshooting help

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Sam,

The most likely problem is a shorted input on the MCU.
As another has pointed out, a leaky C2 could also cause that problem,
but is not the most probable.

The MENU button may not be a problem - if the MCU is busy keying, it
will not respond to button taps.

73,
Don W3FPR

On 5/31/2026 10:33 AM, Sam Smith via Elecraft wrote:
> Mike, thanks for taking the time to respond. I have done lots more tests and narrowed things down.
>
> First off, the K2 is on the bench with a dummy load and power turned down to as low as it will go, so RF is not a problem.
>
> The /DASH line on pin 29 of the MCU is "floating" around 2 volts. I am guessing it should be 5 volts like the /DOT-PTT without keying it. That is what the voltage chart says.
>
> Behavior is erratic. Sometimes when I turn it on it starts keying right away. Or when I touch the paddle. Same thing with a straight key in "hand" mode.
>
> And when it gets in this state the menu button doesn't work, even if it is not keying. All the other buttons seem fine.
>
> I have a scope, so I looked at the /Bank1 and /Bank2 signals - all looks OK.
>
> I checked the 82k resistor network for the /DOT-PTT and /DASH with an ohmmeter - they look fine. 5 volts is there and good. ~80k to 5 volts on both signals. But the dash is not pulling all the way up.
>
> It is erratic - sometimes I can get it back to normal by pulling out the key plug and so forth. But not often.
>
> I removed the bottom panel with the heatsink screws (what a pain) and reheated the key connector and looked at everything down there and traced the dot/dash signals back - all looks fine.
>
> So no obvious solution. I needed to upgrade the MCU firmware anyway, so I ordered one.
>
> It will be few days before I get that, but if you have another suggestion I would appreciate it.
>
> Thanks,
> Sam N4MAP
>
>
>