K2 PLL Reference Osc Range Low

[Jim KO5V]

If I have spammed everyone with multiple copies of the message, I am very sorry. I had to create a new user account, with a new email address, and my attempts were a bit clumsy. My SPAM filter my also reply to any responses, since I'm not sure if my address book copies to the new email address.

All tests and adjustments on my K2 build, up to the PLL Reference Oscillator Range Test, have been nominal. The range is low, at 9.3kHz. The PLL reference oscillator reads 12093kHz, and I adjusted C22 by zero-beating to my RX320 receiver set to 4.000Mhz.

L31 is a 12mH inductor. I swapped X1, but the range decreased, so I reinstalled the original XTAL. I went to p10 of the troubleshooting section in the manual, and found the following:

1. Reference Oscillator Output: Pin 1 of U6 measures 0.7Vrms (should be 0.8-1.8Vrms)
2. VCO Output: Pin 3 of U3, 0.25Vrms (0.30-0.40Vrms)
3. VCO Buffer Output: Pin 6 of U3: 0.55Vrms (0.60-0.75Vrms)

This was an old, unbuilt kit, S/N 212. I purchased new boards, and all parts and firmware to upgrade it to the most current specifications (new S/N 7279). I did not find anything on the Nabble archive, but I wonder if it's something to do with the thermistor board. I have double-checked my soldering. Any ideas?

Thanks in advance, & 73,

Jim KO5V
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[Don Wilhelm-4]

Jim,

You are correct, the problem likely will be found in the soldering of
the Thermistor board.  Do these tests to see if it indicates the problem
source.

Check the voltage at U6 pin 5.  It should be 4 volts - if not, you have
a thermistor board problem
Enter the menu for CAL FCTR - then tap BAND+ and measure the voltage at
U5 pin 7 (should be near 4 volts) and the voltage at U6 pin 1 (should be
near 8 volts).  If those are not correct, you have a problem with the
thermistor board.
If you got close to 8 volts at U6 pin 1 in the last step, check the
voltage at the cathodes of D16 and D17.  If the voltage is not close to
the same thing you read at U6 pin 1, you have a soldering problem at R19
or RP2 or D16 or D17.

If all checked out this far, tap BAND- and read the voltage at U5 pin 7
and U6 pin 1 - this time both should be near zero.

Let me know what you find.

73,
Don W3FPR

On 5/27/2012 1:50 PM, Jim KO5V wrote:

> If I have spammed everyone with multiple copies of the message, I am very sorry. I had to create a new user account, with a new email address, and my attempts were a bit clumsy. My SPAM filter my also reply to any responses, since I'm not sure if my address book copies to the new email address.
>
> All tests and adjustments on my K2 build, up to the PLL Reference Oscillator Range Test, have been nominal. The range is low, at 9.3kHz. The PLL reference oscillator reads 12093kHz, and I adjusted C22 by zero-beating to my RX320 receiver set to 4.000Mhz.
>
> L31 is a 12mH inductor. I swapped X1, but the range decreased, so I reinstalled the original XTAL. I went to p10 of the troubleshooting section in the manual, and found the following:
>
> 1. Reference Oscillator Output: Pin 1 of U6 measures 0.7Vrms (should be 0.8-1.8Vrms)
> 2. VCO Output: Pin 3 of U3, 0.25Vrms (0.30-0.40Vrms)
> 3. VCO Buffer Output: Pin 6 of U3: 0.55Vrms (0.60-0.75Vrms)
>
> This was an old, unbuilt kit, S/N 212. I purchased new boards, and all parts and firmware to upgrade it to the most current specifications (new S/N 7279). I did not find anything on the Nabble archive, but I wonder if it's something to do with the thermistor board. I have double-checked my soldering. Any ideas?
>
> Thanks in advance,&  73,
>
> Jim KO5V
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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