VFOs STUCK on 20m

[Steve Banks]

Hi Everyone,

I just completed doing the A-to-B upgrades on the RF board for K2 S/N 1599.
The rig is about 5 years old and has run very well heretofore.  In addition
to the A-to-B upgrades, I also installed new RF and SSB firmware, added
replacement crystals, and added the keying waveshape mod, VCO shielding, and
thermal stability mods.

As I was finishing up resetting the filters for the third or fourth time, I
discovered that both VFOs A and B are STUCK at one place on the 20m band.
Specifically, VFO A is stuck at 14100.00KHz and B is stuck at 14060.00KHz.
Neither will change frequency.  The LOCK button is not enabled, and all
bands display the requested 5, 6, or 7 digits.  

Twenty meters is the ONLY band exhibiting this STUCK behavior.  All others
are perfectly normal.  Both VFOs change as the VFO knob is turned on every
other band except 20m.  The STUCK 20m band VFOs also occur in all modes.

Anyone have a suggestion for resetting/fixing whatever I might have
dumb-thumbed so I can tune the 20m VFOs as I've always done?

Just FYI the STUCK 20m VFO situation did not show up until about the 4th or
5th hour the rig was operating after all the mods were finished.

Suggestions appreciated.

Steve Banks
K0PQ
K2 S/N 1599
KX1 S/N 00267


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[Don Wilhelm-3]

Steve,

You present a mystery.  There is nothing that I can think of or see in the
schematic that would cause the VFO to be stuck on only one band.  The VFO
lock is not something that is remembered across bands.

Is there any chance that the K2 is going into transmit on 20 meters?  If so,
the K2 will not change frequency while transmiting, but that is just a
guess, I cannot understand why it would be restricted to only one band
unless you have a bad case of RF feedback on 20 meters.

You might want to check the voltage at the left end of R30 for all bands
(VCO Range in the K2 manual) to see if the voltage changes as you turn the
VFO knob - if it does, then the VFO is tuning but the display is not
reflecting the change - I don't know how that could happen but it would be
informative.

Try direct frequency entry for a frequency in the 20 meter band first - if
you even consider doing a master reset, write down your filter and BFO
settings before doing it because they will all restore to the default
values.

73,
Don W3FPR

> -----Original Message-----
>
> I just completed doing the A-to-B upgrades on the RF board for K2
> S/N 1599.
> The rig is about 5 years old and has run very well heretofore.
> In addition
> to the A-to-B upgrades, I also installed new RF and SSB firmware, added
> replacement crystals, and added the keying waveshape mod, VCO
> shielding, and
> thermal stability mods.
>
> As I was finishing up resetting the filters for the third or
> fourth time, I
> discovered that both VFOs A and B are STUCK at one place on the 20m band.
> Specifically, VFO A is stuck at 14100.00KHz and B is stuck at 14060.00KHz.
> Neither will change frequency.  The LOCK button is not enabled, and all
> bands display the requested 5, 6, or 7 digits.
>
> Twenty meters is the ONLY band exhibiting this STUCK behavior.  All others
> are perfectly normal.  Both VFOs change as the VFO knob is turned on every
> other band except 20m.  The STUCK 20m band VFOs also occur in all modes.
>
> Anyone have a suggestion for resetting/fixing whatever I might have
> dumb-thumbed so I can tune the 20m VFOs as I've always done?
>
> Just FYI the STUCK 20m VFO situation did not show up until about
> the 4th or
> 5th hour the rig was operating after all the mods were finished.
>
> Suggestions appreciated.
>
> Steve Banks
> K0PQ
> K2 S/N 1599
> KX1 S/N 00267
>
>

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