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K2 alignment part 2 question

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R Thompson

K2 alignment part 2 question

I'm doing the alignment at the end of part 2 of the assembly. So
far all seems to be well. There is a quirky little thing that I wanted
to ask about.

From page 63, PLL Reference Oscillator Range Test, step 3.

"When you're in frequency counter mode, the BAND+ and BAND- switches can
be used to check the range of the PLL reference oscillator. First, tap
BAND+ and write down the frequency reading below (typically about 12100
KHz). Then tap BAND- and write down this frequency reading (typically
12080-12090 KHz)."

The range is fine, 13.25 KHz, but I noticed that when I tapped the
BAND- switch that the Ref. Low Freq. was only displayed for a short
time, from a fraction of a second to a couple of seconds, and then the
screen went back to the Ref. High Freq.. I was expecting the Ref. Low
Freq. to stay displayed until BAND+ was tapped again, as it does for the
BFO Test on page 65.

Is this normal behaviour for this test? If not, is it anything to
be concerned about?

Thanks,

Ron VE8RT

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Don Wilhelm-4

Re: K2 alignment part 2 question

Ron,

Yes, the frequency should not revert to the high reading - it should stay.
Check the soldering at RF Board U5 carefully for solder bridges and also
J8 pins 15 and 16. Then on the control board check U6 pins 19 and 20 as
well as J8 pins 15 and 16. Make certain all those points are well
soldered. If there is excess solder, wick it away and re-flow the
solder with a hot soldering iron (750 degF or higher)

What I suspect is happening is that the DAC2CS digital signal is going
low at times it should not because it is shorted to another digital line.

If you find nothing in those areas, ask again and I will give you some
other checks that you can do in the analog realm.

73,
Don W3FPR

On 7/8/2011 12:39 AM, R Thompson wrote:

> I'm doing the alignment at the end of part 2 of the assembly. So
> far all seems to be well. There is a quirky little thing that I wanted
> to ask about.
>
> From page 63, PLL Reference Oscillator Range Test, step 3.
>
> "When you're in frequency counter mode, the BAND+ and BAND- switches can
> be used to check the range of the PLL reference oscillator. First, tap
> BAND+ and write down the frequency reading below (typically about 12100
> KHz). Then tap BAND- and write down this frequency reading (typically
> 12080-12090 KHz)."
>
> The range is fine, 13.25 KHz, but I noticed that when I tapped the
> BAND- switch that the Ref. Low Freq. was only displayed for a short
> time, from a fraction of a second to a couple of seconds, and then the
> screen went back to the Ref. High Freq.. I was expecting the Ref. Low
> Freq. to stay displayed until BAND+ was tapped again, as it does for the
> BFO Test on page 65.
>
> Is this normal behaviour for this test? If not, is it anything to
> be concerned about?
>
> Thanks,
>
> Ron VE8RT
>
> ______________________________________________________________
> 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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Help: http://mailman.qth.net/mmfaq.htm
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R Thompson

Re: K2 alignment part 2 question

Hi Don,

I took it in to work today, to use some of the test gear during my
lunch hour. U5 pin 3 (LD/CS) looks good. There is a steady high on
this pin (measurements made on the IC pins, not on the board, to rule
out soldering problems at the board) with good well shaped pulses
pulling it low. Pulses on pin 2, DIN, appear to be OK. VOUT on pin 7
makes sharp transitions between the high and low states. Unfortunately
I was working with only one scope probe, I really wanted to see if there
was a second DAC2CS pulse on pin 3 that coincided with the undesired
toggle back to the high state (on VOUT), but failed to catch it. My
lunch time is too short, I used some of it to go over the Part II
alignment using the calibrated shop gear.

At the moment, it appears to me that it may be software or digital
problem. The software level on my PIC is 2.04R.

Any thoughts? Everything else in the part II alignment went well, no
problems, error codes, or other discrepancies of any kind, thankfully.

Ron VE8RT

On Fri, 2011-07-08 at 08:13 -0400, Don Wilhelm wrote:

> Ron,
>
> Yes, the frequency should not revert to the high reading - it should stay.
> Check the soldering at RF Board U5 carefully for solder bridges and also
> J8 pins 15 and 16. Then on the control board check U6 pins 19 and 20 as
> well as J8 pins 15 and 16. Make certain all those points are well
> soldered. If there is excess solder, wick it away and re-flow the
> solder with a hot soldering iron (750 degF or higher)
>
> What I suspect is happening is that the DAC2CS digital signal is going
> low at times it should not because it is shorted to another digital line.
>
> If you find nothing in those areas, ask again and I will give you some
> other checks that you can do in the analog realm.
>
> 73,
> Don W3FPR
>
> On 7/8/2011 12:39 AM, R Thompson wrote:
> > I'm doing the alignment at the end of part 2 of the assembly. So
> > far all seems to be well. There is a quirky little thing that I wanted
> > to ask about.
> >
> > From page 63, PLL Reference Oscillator Range Test, step 3.
> >
> > "When you're in frequency counter mode, the BAND+ and BAND- switches can
> > be used to check the range of the PLL reference oscillator. First, tap
> > BAND+ and write down the frequency reading below (typically about 12100
> > KHz). Then tap BAND- and write down this frequency reading (typically
> > 12080-12090 KHz)."
> >
> > The range is fine, 13.25 KHz, but I noticed that when I tapped the
> > BAND- switch that the Ref. Low Freq. was only displayed for a short
> > time, from a fraction of a second to a couple of seconds, and then the
> > screen went back to the Ref. High Freq.. I was expecting the Ref. Low
> > Freq. to stay displayed until BAND+ was tapped again, as it does for the
> > BFO Test on page 65.
> >
> > Is this normal behaviour for this test? If not, is it anything to
> > be concerned about?
> >
> > Thanks,
> >
> > Ron VE8RT
> >
> > ______________________________________________________________
> > 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
> >

Don Wilhelm-4

Re: K2 alignment part 2 question

Ron,

It is very difficult to detect a 2nd pulse on the DAC2CS signal with a
regular 'scope - a digital 'scope that is conditioned to trigger on
events where DAC2CS goes low is required to capture the culprit.

Did you confirm that U5 pin 7 goes to a high state and stays there when
BAND- is tapped?
It should do that. If it stays high for a while and then goes low, the
problem has to be that the DAC2CS went low in the interim period.

Failure of parts in any kit is a rare thing. Assembly problems are the
usual cause of failures.

73,
Don W3FPR

On 7/8/2011 7:39 PM, R Thompson wrote:

> Hi Don,
>
> I took it in to work today, to use some of the test gear during my
> lunch hour. U5 pin 3 (LD/CS) looks good. There is a steady high on
> this pin (measurements made on the IC pins, not on the board, to rule
> out soldering problems at the board) with good well shaped pulses
> pulling it low. Pulses on pin 2, DIN, appear to be OK. VOUT on pin 7
> makes sharp transitions between the high and low states. Unfortunately
> I was working with only one scope probe, I really wanted to see if there
> was a second DAC2CS pulse on pin 3 that coincided with the undesired
> toggle back to the high state (on VOUT), but failed to catch it. My
> lunch time is too short, I used some of it to go over the Part II
> alignment using the calibrated shop gear.
>
> At the moment, it appears to me that it may be software or digital
> problem. The software level on my PIC is 2.04R.
>
> Any thoughts? Everything else in the part II alignment went well, no
> problems, error codes, or other discrepancies of any kind, thankfully.
>
> Ron VE8RT
>