http://elecraft.85.s1.nabble.com/K2-Alignment-and-Test-Part-II-issues-tp7645364p7645373.html
The main 8 volt and 5 volt regulators are on the Control Board. You will
>
> Don,
>
> Board U6 pin 5
>
> Thank you for the suggestions! The DC voltage at RF Board U6 pin 5 is
> 0 volts. In fact, all pins of U6, except pin 6, are 0 volts. Pin 6 is
> less than 1 volt.
>
> I saw a bridge between C96 and RFC10, the schematic shows these two
> components connecting together, so that should be ok. I’m still
> looking for bridges.
>
> Could you elaborate a little on the ^voltage rail*? How do I identify
> the rail on a schematic, or can I? Which component is the 8 volt
> regulator? I feel I should know the answers to these questions, I must
> be having a senior moment. Your help and advice is much appreciarted!
>
> Thanks!
>
> Don, KE0PVQ
>
> Sent from Mail <
https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
> *From: *Don Wilhelm <mailto:
[hidden email]>
> *Sent: *Thursday, September 27, 2018 11:01 AM
> *To: *Don Schroder <mailto:
[hidden email]>;
>
[hidden email] <mailto:
[hidden email]>
> *Subject: *Re: [Elecraft] K2 Alignment and Test, Part II issues
>
> Don,
>
> First check the DC voltage at RF Board U6 pin 5 - it should be 4 volts
>
> (or 1/2 the 8 volt regulator output voltage). If it is not correct, you
>
> have a problem with the thermistor board - most likely a solder bridge.
>
> You should have 8 volts at the thermistor board pin 8. If that is not
>
> correct, look carefully for solder bridges. That 8 volts comes directly
>
> from the 8 volt regulator voltage rail.
>
> It does sound like you have a problem with the PLL Reference Oscillator,
>
> but your voltage measurements on the thermistor board pins should be
>
> investigated first before drawing any other conclusions.
>
> Make sure you have good results with the PLL range tests just after that.
>
> The exact frequency of the 4 MHz Oscillator is not critical at this
>
> point - for now it only substantiates that the oscillator is working. If
>
> you put a probe on C22, it will pull the frequency. If your frequency
>
> counter is sufficiently accurate, wait until you have a good frequency
>
> at TP1, and then measure the frequency with both the counter and the
>
> internal counter probe using CAL FCTR. Adjust C22 so CAL FCTR frequency
>
> is the same as your external counter.
>
> I do not know the accuracy of your counter, but mine is accurate to 10
>
> exp-9 and I can set C22 with it for good K2 Dial Calibration. There are
>
> other methods for setting C22 that do not depend on the accuracy of your
>
> frequency counter. When you can receive WWV at 10 or better 15 MHz,
>
> look at my website www.w3fpr.com article on K2 Dial Calibration to
>
> accurately set C22 and achieve good K2 dial calibration.
>
> 73,
>
> Don W3FPR
>
> On 9/26/2018 8:14 PM, Don Schroder wrote:
>
> > Hi folks,
>
> >
>
> > Got to the subject location on my K2 kit #7818, and am having some
> difficulties with the tests. My frequency counter, when touched to the
> left side of trimmer capacitor C22, reads 3999.98 on the LCD. This
> makes me believe there is no problem with the frequency counter probe
> that I assembled.
>
> >
>
> > On page 63, under *4 MHz Oscillator Calibration, I selected CAL
> FCTR, and the LCD displays a rapidly changing frequency between 185.~
> to 188.~. It does not show a frequency of 12090 kHz suggested by the
> manual. This tells me I have a problem with the PLL Reference
> Oscillator (since the frequency counter probe appeared to be ok). I
> then decided to check voltages, and discovered that I am missing some
> +5v signals from U4 and U5.
>
> >
>
> > Any suggestions on where to look next? I’d like to trace the 5v
> signals, but I don’t see how to do that using the schematics. I did
> measure voltages on the 8 pins of the Thermistor Board, they were all
> 0 volts! That didn’t seem right, either.
>
> >
>
> > Appreciate any suggestions! Thanks!
>
> > Don, KE0PVQ
>
> >
>
> > Sent from Mail<
https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
> >
>
> > ______________________________________________________________
>
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