Sam,
What is the firmware level in that K2, and what is the serial number?
Does it have either the KIO2 or KPA100 installed?
Those may sound like questions that are not relevant, but if the
firmware is downlevel and the SN is below 3000, you may have to make
some changes to the control board (not difficult) when you upgrade the
firmware.
Those are the same changes that must be added when the KIO2 or KPA100 is
added to a level A K2. It is just 1 cut, and one wire add along with a
.001 uF capacitor.
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
On Sunday, May 31st, 2026 at 8:14 AM, Michael Carter via Elecraft
<[email protected]> wrote:
Hi Sam,
You identified two issues with your recently acquired K2: rig locked into
transmit mode after using a straight key, and lack of response to MENU button
presses. It's not immediately apparent to me that these issues are connected
causally, i.e. that the MENU button malfunction was caused by the event that
caused the rig to lock up in transmit mode.
Had you been using a straight key for some time prior to the transmit lockup?
You mention alternating between straight key and paddle. How do you have the
KEY input wiring configured to share the KEY input between the straight key and
the paddle?
As with all of the front panel buttons, the MENU button serves two functions: a
short press opens the MENU options, a long press opens the EDIT function. From
your report, there are no MENU options visible on the display with a short
press of that button?
The K2 control design strobes each of the buttons sequentially and looks for
switch closure. The MENU button is strobed upon activation of the /BANK1
signal (logic low) AND sampling of the D7 input to the parallel-to-serial
converter. D7 is also used for the XIT/PF2 button sensing when the
/BANK2 signal is asserted. Please check that the XIT button is responsive to
both short and long presses. If so, that suggests that the MENU button has a
mechanical failure or there may be a weak solder joint under it that has opened
under repeated button presses.
I'll give some more thought to the transmit lockup issue later today. I've not
experienced that kind of lockup with my K2 except when there was excessive RF
induced on the external wiring due to common-mode currents in the antenna
connection.
73,
Mike, K8CN
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