[Elecraft] K2 Troubleshooting help

[W3FPR]

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
>
>
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