Re: RE: K2 Alignment & Test, Part II PLL problem, Continued

[rootboy-3]

Okay, I'll give that a try.

And as always, thanks for your time.

John

>
> From: "Don Wilhelm" <[hidden email]>
> Date: 2006/04/19 Wed AM 07:51:00 CDT
> To: <[hidden email]>
> Subject: RE: K2 Alignment & Test, Part II PLL problem, Continued
>
> John,
>
> It is also possible that you have a sluggish PLL reference crystal.  I don't
> know of a check other than replacing it.
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> > From: [hidden email] [mailto:[hidden email]]
> > Sent: Wednesday, April 19, 2006 4:01 AM
> > To: [hidden email]
> > Cc: [hidden email]
> > Subject: Re: RE: [Elecraft] K2 Alignment & Test, Part II PLL problem,
> > Continued
> >
> >
> > I'm back....
> >
> > I got the new components (D16, D17, C84, C85, & Q19) from Scott
> > over at Elecraft and installed them. I still got the same
> > readings so I re-read the instructions and checked each and every
> > component to make sure that I had everything installed correctly.
> >
> > I did find one mistake, I had soldered C88 to pins 11 & 12 of U4
> > instead of pins 12 & 13. I relocated the cap and the frequency
> > went up slightly (reading 524 instead of 495). The cap measured
> > ~58 picos (in circuit) so it's in the ballpark.
> >
> > I also touched up a few soldering joints along the way, more for
> > looks than anything else.
> >
> > The voltage readings on pins 1, 2, & 3 of U6 are the same as
> > before, and both variactors seem to be working just fine.
> >
> > Any ideas?
> >
> >
> > Thanks again for all of your help,
> >
> > John
> >
> >
> > >
> > > From: "Don Wilhelm" <[hidden email]>
> > > Date: 2006/04/11 Tue PM 08:18:46 CDT
> > > To: <[hidden email]>,
> > > <[hidden email]>
> > > Subject: RE: [Elecraft] K2 Alignment & Test, Part II PLL
> > problem, Continued
> > >
> > > John,
> > >
> > > For the time being (until you solve the current problem) the
> > only voltages
> > > at U6 that matter are pins 1, 2 and 3 - and those are correct.
> > The other
> > > pins will likely fall into line after you have this problem
> > fixed and if not
> > > there is another problem with the VCO.
> > >
> > > Right now, the voltages being fed out of U6 pin 1 are correct for the
> > > stimulus you provided (CAL FCTR and tapping BAND+ and BAND-).
> > Now check to
> > > see if that (proper) 0 to 8 volt swing between pressing BAND+
> > and BAND- is
> > > carried on through R19 and then through the RP2 sections and
> > then onto the
> > > cathodes of D16 and D17.  If you get a decent voltage swing
> > between BAND+
> > > and BAND- (you can expect a bit of voltage drop on the 8 volts
> > end) at the
> > > varactor cathodes, then look for something else wrong in the
> > PLL Reference
> > > oscillator (upper left of the schematic sheet - but only as far
> > to the right
> > > as TP3), the PLL chip does not matter until the PLL Reference
> > oscillator is
> > > functioning properly.
> > >
> > > If you do get a good voltage swing at the varactors, then all I
> > can say is
> > > either Q19 oscillations quit when the varactor capacitance is
> > reduced, or
> > > there is something wrong at C84, C85, D17 or D16 which is stopping the
> > > oscillation.  If you suspect Q19 itself, you could try swapping
> > it with one
> > > of the J310s on the Control Board at Q6 or Q7 (these in a less-critical
> > > audio circuit rather than being used as an RF Oscillator).
> > >
> > > 73,
> > > Don W3FPR
> > >
> > > > -----Original Message-----
> > > >
> > > > Thanks for the help Don. :)
> > > >
> > > > I tried your suggestions (and a few others as well) and L31
> > > > (which is a 12 µHz inductor on my unit) is the correct part.
> > > >
> > > > Diodes D16, D17, & D18, are in properly and pass their in-circuit
> > > > tests just fine.
> > > >
> > > > R19, RP2, R20, R21, RFC14, C84, C85, Q19, RFC14, Q19 and the
> > > > thermistor board are all installed properly and certainly look good.
> > > >
> > > >
> > > > Scott at Elecraft suggested holding the 4, 5, & 6 buttons while
> > > > turning the unit on (which showed "INFO 201") to see if that
> > > > corrected the problem but no luck there either.
> > > >
> > > > I took reading off of U6 while switching between "BAND -" and
> > > > "BAND +" in "CAL FCTR" mode, and here's what I got:
> > > >
> > > > BAND +, The display reads 488Hz  (Bad)
> > > >
> > > > U6 Readings:
> > > > Pin 1 = 7.63V
> > > > Pin 2 = 4.09V
> > > > Pin 3 = 4.09V
> > > > Pin 4 = 0V
> > > > Pin 5 = 3.96V
> > > > Pin 6 = 4.91V
> > > > Pin 7 = .02V
> > > > Pin 8 = 7.95V
> > > >
> > > >
> > > > BAND -, The display reads 12086Hz  (Good)
> > > >
> > > > U6 Readings:
> > > > Pin 1 = .00V
> > > > Pin 2 = .09V
> > > > Pin 3 = .02
> > > > Pin 4 = 0V
> > > > Pin 5 = 3.96V
> > > > Pin 6 = 3.96V
> > > > Pin 7 = 1.64V
> > > > Pin 8 = 7.95V
> > > >
> > > >
> > > > Pins 2, 3, 6, especially Pin 6, are out of tolerance.
> > > >
> > > > Taking resistance readings off of the thermistor board looks good.
> > > >
> > > > Pins 6/7 to Pin 8 reads about 5k ohms.
> > > > Pins 4/5 to Pin 8 reads about 295 ohms.
> > > > Pins 2/3 to Pins 4/5 reads about 1.96k ohms.
> > > > Pins 6/7 to Pin 1 reads about 8.76k ohms.
> > > > Pin 1 to Pins 2/3 reads about 1.8k ohms.
> > > >
> > > > All of these readings more or less mathematically work out to
> > > > what the meter says (with the exception of the second reading
> > > > which is 8V to Ground so no surprise there).
> > > >
> > > > The output from the DAC is 4.092 (4,092 counts), so it's near its
> > > > top end.
> > > >
> > > >
> > > > My partner suggests removing R19 and inserting a pot to swing the
> > > > voltage going into the oscillator circuit from 0 to 7-ish volts
> > > > to see if that stabilizes.
> > > >
> > > >
> > > > I got another suggestion to double check D36 for proper
> > > > installation. It's in correctly, and checks out (in circuit) okay.
> > > >
> > > > Possibly I left a component out, so I'll double check that I
> > > > didn't skip anything during the installation phase.
> > > >
> > > >
> > > > Thanks again for all the help,
> > > >
> > > > John
> > > >
> > > >
> > >
> > >
> >
> >
> >
> > --
> > No virus found in this incoming message.
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> > Version: 7.1.385 / Virus Database: 268.4.3/317 - Release Date: 4/18/2006
> >
> >
>
>

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