You have it right Chris. I believe the initialization of that linearisation
table that is locking it all up and driving the 12 bit DAC to max voltage.
Cal PLL will not work because there is no lock. So it is stuck.
Still need to track down the problem and then I'm thinking we have to come
up with a way to redo the table to something nominal to move forward.
73,
Dave, W8FGU
On May 21, 2019 11:21:32 "Chris Smith" <m...@m0xte.uk> wrote:
Hi,
Thanks for the reply. Much appreciated.
That’s a bummer. Is there anything I can do here with the current EEPROM? I
have a programmer available. I assuming erasing it and letting the K2
reinitialise it a small per earlier steps won’t resolve this?
Based on looking at it from the outside naively, it feels like theres
something up with the VCO linearisation as it’s sending the control word on
VFO steps but the same data. I’ll get a bus captures if it helps.
Assume that performing the VCO linearisation steps later won’t fix it either?
Hope you enjoy your vacation - sounds nice!
Best regards,
Chris M0XTE
On Tue, 21 May 2019, at 18:11, Dave Van Wallaghen wrote:
Chris,
I have worked on a few late model K2'S of late with the exact same problem.
The folks in support are currently looking into it to determine the source
of the problem.
My solution was to replace the Control board EEPROM with a known properly
initialized one and everything came back to life. I even discussed this
with Wayne in Dayton. We're looking into whether we have an EEPROM issue or
a possible programming anomaly with the main PIC MCU.
I'm currently on vacation with my wife 8 miles off the coast of Belize. I
have limited WIFI but will continue to check in.
Stay tuned...
73,
Dave, W8FGU
On May 21, 2019 10:28:00 "Chris Smith" <m...@m0xte.uk> wrote:
Hi,
I've just completed my K2 up to the PLL reference oscillator.
Initially when I assembled it the PLL reference oscillator would not
oscillate at all. No reading on internal counter. I popped it on my
external Racal counter and still dead. After tracing the problem out I
found that the voltage on input to the varactors was pegged at 7.07V which
was too high for the oscillation to carry on. I lifted one end of R19 on
the output of U6A and the thing oscillates fine isolating this to a control
voltage problem.
Next I checked voltages on the thermistor board and input of the opamp. All
good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at
4.095V (top end of DAC range by the looks of it) which is forced up by the
opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same
data word to the DAC every time regardless of VFO position. The CLK and CS
lines are doing their thing correctly.
Anyone got any ideas why the control word is the same? VFO reading on
display is changing fine.
What can I do to get out of this hole?
Any help appreciated.
Best regards,
Chris M0XTE
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