New build K2 with VFO tuning problems

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New build K2 with VFO tuning problems

MCU Version 2.04 and IO 1.09

Hi all,
I am commissioning a K2 for our radio club that was started by someone else (silent key).  I have worked through quite a list of build errors but have now got the basic opertion of the radio working.

But I have one problem with the VFO that has me stumped so far and so need some help.

It will tune ok on the course setting, but selecting the finer tuning rates makes it tune in jumps (around 5kHz).  Nothing happens while turning the tuning knob, and then it jumps in frequency.

Looking at the control signals from the MCU to the syntheziser IC, the Enable line (/PLLCS) is not going low on these finer rate settings when turning the tuning encoder; it does on the course setting. The clock and data lines however do look like they are working ok.

All other uses of the encoder are working fine, so I don't think that is involved. And the LCD display shows the changing frequency fine also.  It's just the updates to the synthesizer that are not being output properly.

If the MCU is updating the LCD display correctly, how come it is not doing the same to the synthesizer? All very strange.

Any help in sorting this out would be much appreciated.