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K2 rotary encoder

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Josh Gibbs

K2 rotary encoder

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.

73,

-Josh WU7H
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Don Wilhelm-5

Re: K2 rotary encoder

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.
>
>

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Josh Gibbs

Re: K2 rotary encoder

Thank you Don. Confirmed I have 7.8V at anode of D6 and zero at anode of D7
in RX.

U3 is a TPIC6B595N which is in stock at the usual online electronics
retailers and very inexpensive.

73,

-Josh WU7H

On Thu, May 27, 2021 at 1:33 PM Don Wilhelm <[hidden email]> wrote:

> 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.
> >
> >
>
>

Josh Gibbs

Re: K2 rotary encoder

Quick update on my K2. The new TPIC6B595N turned up on my doorstep this
afternoon and my K2 is now 100% operational once again.

Thanks again for your help Don.

73,

-Josh WU7H

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.
>>
>>
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