[Elecraft] [K2] VCO Test fail

Stephen vk2rh stephen.vk2rh at gmail.com
Thu Jan 6 23:32:18 EST 2011


I'm enjoying building K2 #7076 and have made it to the Alignment and
Test, Part II section on page 63 of the revision H manual.

I've completed the 4MHz Oscillator Calibration check and the PLL
Reference Oscillator Range Test and the K2 is within expected spec.

For the 4 MHz Oscillator Calibration the counter reading was 12098.69
with regular fluctuation 10-20 Hz or so. Is that okay or a sign of
trouble ahead? Wasn't sure whether this was what the manual meant by
'changing rapidly' and whether the readout needs to be rock steady or
not. I've used both an external frequency counter and a K3. The signal
sounds solid to my old ears!

Assuming it was okay I proceeded on to the PLL Ref. Oscillator Range
Test. This yielded a range of 12.46 kHz - within acceptable range from
9.8 - 15 kHz.

However the VCO Test on page 63 results in a frequency of 7470.10
instead of one within the acceptable 8 - 10 MHz range. It's not clear
which parts of the troubleshooting advice apply at such an early
alignment stage. I've checked and re-checked components and solder
joints in the PLL Reference Oscillator and the PLL Synthesizer parts
of the board.

So I'd like any advice about what I need to check or do to get the VCO
Test to land within the correct 8 - 10 MHz frequency range. Most
advice I could find via searching previous email discussions was about
the VCO Alignment which is the next stage, but I figure I need to get
over this hurdle before that next one.

73
Stephen VK2RH


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