[Elecraft] Alignment & Test II

Tue Aug 22 22:42:56 EDT 2006

Don, thanks for the help, at least I think we are getting close to solving
this mystery to me.  I can converse with you on tubes, but this solid state
stuff is new to me.  Shows you how old I is.

Pin 1 of U1 has 6 volts present and will not go to zero as you suggested.
Pin 3 of U1 reads zero.  As you indicated that is my problem.

Following the steps in the manual and your advice I was able to get the high
reading of 12101.18 and the low 12091.42. The following voltages are:  U6,
Pin 1 high 7.64v and low 11.4 microvolts (?); U6 Pin 3 high 4.06v and low
11.4 microvolts.  I measured Pin 20 of U6 to be 6 volts.

I lifted R19 and the readings were 4.08 before and 7.64 afterwards.

I removed the thermistor board and checked the resistors and found no
errors.  I examined the board around the thermistor and found no solder
bridges as you suggested I might have.

Anyway, I think you are about to resolve my issues to which I appreciate.

Dwight  W4IJY  K2 #4766 
-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at earthlink.net] 
Sent: Monday, August 21, 2006 10:32 PM
To: C Dwight Baker
Subject: RE: [Elecraft] Alignment & Test II

Dwight,

The real problem is that U1 pin 1 is not going to zero.  Now take a tiny
step to try to discover the cause - do the same test of the PLL range (you
can ignore the frequencies for this), but check the voltage at U6 pin 3 when
the BAND+ button is tapped and also when the BAND- button is tapped.  We
want to see the voltage at pin 3 go from about 4 volts to about zero volts.

If you do get the 0 to 4 volt swing at pin 3, then the firmware and DAC are
doing the job properly, you will find the problem on the thermistor board,
and the most likely is a solder bridge between pins 5 and 6 - the pads get
quite close to each other there and a solder bridge is easy to create.

The 0 to 4 volt swing at U6 pin 3 should make the voltage at U6 pin 1 swing
from 0 to 8 volts if the resistors in the op amp circuit (mainly the
thermistor board) are correct.  If you need to convince yourself that the
pin 1 output is not being loaded down, just lift one end of R19 and repeat
the test.  U6 should have twice as much voltage on pin 1 as is put onto pin
3 when all is well with the resistor network.

73,
Don W3FPR

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net]On Behalf Of C Dwight Baker
> Sent: Monday, August 21, 2006 8:52 PM
> To: elecraft at mailman.qth.net
> Subject: RE: [Elecraft] Alignment & Test II
>
>
> Don, I followed your suggestions and I am still at the same place
> I started.
>
>
> I began by following the schematic as you suggested and marked each
> component as I verified the correct values and type.  I found no
> errors (at
> least I didn't but it doesn't mean I erred again).
>
> It appears I had a solder bridge between pins 4 and 5 on U6.  I
> replaced D16
> veractor MV209 and did not have another D17 ISV149 so the old one is still
> there.
>
> The readings remained virtually the same as before.  The voltages
> at U6 pin
> 1 were as follows:  High 12103.15, voltage 7.61; low 1209.03,
> voltage 3.74.
>
> Pin 8 of the thermistor board was 7.97 and pins 6 and 7 measured
> 3.96.  Pin
> 1 measured 7.64.  The line voltage at the power plug was 14.3 volts.
>
> I am curious why the voltage on the lower reading did not go to near zero.
> Would Q19 (J310), D17 be faulty and what effect does U4 have?
>
> I appreciate your time for leading this BOOF (burnt out old f-rt) through
> the dark.
>
> Thanks again,
>
> Dwight W4IJY  K2 4766
> -----Original Message-----
> From: Don Wilhelm [mailto:w3fpr at earthlink.net]
> Sent: Monday, August 21, 2006 9:17 AM
> To: C Dwight Baker; elecraft at mailman.qth.net
> Subject: RE: [Elecraft] Alignment & Test II
>
> Dwight,
>
> Don't be concerned about the setting of C22 until after you have finished
> the entire build - just set it to mid-position for now.  You will want to
> re-do CAL PLL and CAL FIL after you are done with the 4 MHz oscillator set
> precisely to achieve good dial calibration.  The K2 does not use the 4 MHz
> oscillator on a real time basis, only during CAL PLL and CAL FIL
> operations.
>
> Now in to your problem.  Yes, your PLL high and low frequencies
> are too high
> and the range is too small.
> Turn your manual to the back and find the schematic for the RF
> Board - sheet
> 1.  Then find the area in the left upper corner marked PLL Reference
> Oscillator.  Check all the components associated with that circuit,
> especially the capacitors, varactors, and inductor L31 for proper
> values and
> make certain they are in the correct holes.  Re-verify that D16
> and D17 are
> correct - D16 is the larger bodied varactor and D17 is the smaller.
>
> After verifying the components above, go back to CAL FCTR with
> the probe in
> TP3, tap the BAND+ button and read the high frequency, then measure the
> voltage at U6 pin 1 (it should be near 8 volts).
> Then tap the BAND- button and read the low frequency and measure
> the voltage
> at U6 pin 1 (now should be near zero volts).
>
> Did you obtain a correct frequency range? Did the voltage at U1
> pin 1 change
> from 8 volts to 0 volts?
> Let us know what you find.
>
> 73,
> Don W3FPR
>
>
> > -----Original Message-----
> >
> > When I did the PLL reference oscillator range test and at 4 MHz; the
> > readings are 12104.45 on the high end and 12099.20 at the low end for a
> > difference of 5.25 whereas the manual indicates the range should be
> > somewhere between 9.8 and 15 kHz.
> >
> >
> >
> > Adjusting C22 on the control board gives me a difference of 5.5 kHz.
> >
> >
> >
> > Where or what am I looking for or better yet have I goofed in
> > populating the
> > board?  Phase I testing was good.
> >
> >
>
>
>
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