[Elecraft] K2 rotary encoder

[Don Wilhelm]

Josh,

Your investigation is "spot on" and I would normally recommend replacing 
Front Panel U3.  It is possible for it to have one bad input and is 
quite static sensitive.

But first, check that 8R and 8T signal lines are working properly.  An 
easy place to check is at the anodes of RF Board D6 and D7.
The anode of D6 should be near 8 volts during receive and the anode of 
D7 should be close to zero.
That situation will reverse during transmit.

If you find 8R and 8T are on at the same time, that could be reason for 
the problem.
If you have a problem with those signal lines, check back on the control 
board at Q1, Q2, Q3 and Q4 to determine where the problem might be.

73,
Don W3FPR

On 5/27/2021 4:15 PM, Josh Gibbs wrote:
> My K2 (SN: 4073) suffered a sudden problem yesterday. I didn't notice
> anything happening - one minute it was working normally and the next the
> VFO knob stopped working.
>
> All other functions appear to be working normally, but the rotary encoder
> is disabled.
>
> If I ground the V- pin (via 100 ohm resistor) the encoder comes to life and
> functions normally.
>
> I have verified good continuity between encoder V- and pin 14 of U3.
>
> In the manual it says that the MCU can disable the encoder under certain
> operating conditions. What might those conditions be? One thought I have is
> that the MCU is disabling it for some reason.
>
> My current plan is to try replacing U3. All other functions of U3 appear to
> be working.
>
> Any troubleshooting advice would be appreciated. Thanks for reading.
>
>