K2 Alignment & Test, Part II PLL problem, Continued

[rootboy-3]

Just an update:

Following the advice that I had found on this list, I desoldered the crystal and checked for solder balls. It was clean.

I also checked the voltage on pin 5 of U6 and it was 4 volts.

I looked at the thermistor board and it looked good.

I watched the signal using a scope and with the radio setup for the "CAL FCTR" test,
I had a reading of ~400hz and nothing but noise on TP3.

Once I pressed the "BAND - " button, I got the expected 12,090hz signal and a reasonably pretty sine wave on TP3.

Pressing the "BAND +" or turning the tuning knob would send it back to ~400hz and the signal would revert to noise.


Any thoughts?


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[Don Wilhelm-3]

Be certain you have correctly installed L31 and that it is the 10 uH
shielded inductor.  Resistor R115 is about the same size - is there a
possibility that you exchanged these parts?

Be certain you have D16, D17 and D18 inserted the proper way around (the
Parts Placement Diagram is handy for checking diode orientation).  Check the
soldering on these diodes.

Be certain R19 and RP2 is well soldered.  While you are checking soldering,
also check R20 and R21, RFC14 C84 and C85, and Q19.  You can check the
toroid lead soldering for RFC14 by measuring the resistance to ground from
the source of Q19 - expect a small bit more than 270 ohms.

73,
Don W3FPR

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]]On Behalf Of
> [hidden email]
> Sent: Saturday, April 08, 2006 1:28 AM
> To: [hidden email]
> Subject: [Elecraft] K2 Alignment & Test, Part II PLL problem, Continued
>
>
> Just an update:
>
> Following the advice that I had found on this list, I desoldered
> the crystal and checked for solder balls. It was clean.
>
> I also checked the voltage on pin 5 of U6 and it was 4 volts.
>
> I looked at the thermistor board and it looked good.
>
> I watched the signal using a scope and with the radio setup for
> the "CAL FCTR" test,
> I had a reading of ~400hz and nothing but noise on TP3.
>
> Once I pressed the "BAND - " button, I got the expected 12,090hz
> signal and a reasonably pretty sine wave on TP3.
>
> Pressing the "BAND +" or turning the tuning knob would send it
> back to ~400hz and the signal would revert to noise.
>
>
> Any thoughts?
>
>
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>
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