[Elecraft] K2 PLL reference oscillator test failure

[Harlan Braude]

I sent this before the Memorial Day weekend, but haven't seen a response, so
I'm sending it again in case it was missed...

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Hi gang!

With serial #3398, I'm getting the "changing rapidly" syndrome
when I perform the "4 MHz Oscillator Calibration" step on pg 57
of the K2 manual (Rev E, 02/16/03).

I confirmed that the frequency counter probe itself is working by
repeating the test from page 45 (the F.Counter showed ~3999.)

I also confirmed that I have the correct IC in U4 and the solder
connections look fine under magnification.

I did apply the change described in the "K2 Manual Errata" (Rev
E-2, 03/12/03), which involves soldering C91 and RFC15 on the
bottom of the RF board between pin 16 of U4 and the pad that pin
16 had been connected to in earlier versions of the RF board.

I've gone over that modification, too, and it seems fine to me.

Is replacing U4 the next step or are there other possibilities I should look
into first?

Suggestions would be appreciated.

Thank you.

Regards,
Harlan
KC2KUK