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K1 VFO problem

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David L DuPuy

K1 VFO problem

K1 VFO PROBLEM: I’m building a K1, and have reached the mid-point on
populating the RF board, at the Alignment and Test, Part I (page 36). All
looks well until I get to VFO Range Test on p. 38, and I get E42 (VFO not
functioning). The previous resistance and voltage checks were all fine.

I have indeed looked carefully for wrong components or bad solder joints,
and all looks well. (I’m using a Weller WP-25 iron and have plenty of
experience with soldering, and re-checked very carefully with a quality
magnifying glass!)

I see a clean VFO signal on pin 1 of U7 (premix), and the same signal on
the emitter of Q9 (buffer). I see only hash on the side of C8 that goes to
P1 pins. The amplitude is only 0.07 volts... is it really supposed to be
that small??! The frequency is approximately 3030 (using analog
oscilloscope), which appears close to the 3090 minimum; I have not yet
gotten to the next page where the VFO range is adjusted.

On U7, pin 6 (to the crystal X1) I see a ragged, low amplitude signal which
appears to be the expected 15.00 MHz... but it sure is messy. I have
carefully checked continuity from U7 pin 6 to pin 9 on K1A on the filter
board, and that’s fine.

Can anyone tell me if this sounds like a problem upstream of Q8? Or maybe
a problem with U7? Many thanks... Sure am glad to find this Elecraft
reflector! David AC4BN
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Don Wilhelm-4

Re: K1 VFO problem

David,

Yes, it does seem to be a problem between C8 and the MCU input on the
Front Panel.
If you are getting good oscillation at the VFO (Q9 buffer) then check
continuity from C8 to the base of Front Panel Q1 - that should give you
a good check on the path continuity. Also check resistance to ground to
be certain there are no shorts.

The path from FP Q1 collector goes directly to the MCU pin 6, so check
continuity there too. Make certain that FP R11 and R12 are the correct
values.

The VFO frequency reading and the E42 error message have nothing to do
with U7, but after you solve the VFO counter problem, there may be
another problem lurking if you found no oscillation at U7 pins 6 and 7 -
hold that situation until later.

73,
Don W3FPR

On 3/4/2013 2:11 PM, David L DuPuy wrote:

> K1 VFO PROBLEM: I’m building a K1, and have reached the mid-point on
> populating the RF board, at the Alignment and Test, Part I (page 36). All
> looks well until I get to VFO Range Test on p. 38, and I get E42 (VFO not
> functioning). The previous resistance and voltage checks were all fine.
>
> I have indeed looked carefully for wrong components or bad solder joints,
> and all looks well. (I’m using a Weller WP-25 iron and have plenty of
> experience with soldering, and re-checked very carefully with a quality
> magnifying glass!)
>
> I see a clean VFO signal on pin 1 of U7 (premix), and the same signal on
> the emitter of Q9 (buffer). I see only hash on the side of C8 that goes to
> P1 pins. The amplitude is only 0.07 volts... is it really supposed to be
> that small??! The frequency is approximately 3030 (using analog
> oscilloscope), which appears close to the 3090 minimum; I have not yet
> gotten to the next page where the VFO range is adjusted.
>
> On U7, pin 6 (to the crystal X1) I see a ragged, low amplitude signal which
> appears to be the expected 15.00 MHz... but it sure is messy. I have
> carefully checked continuity from U7 pin 6 to pin 9 on K1A on the filter
> board, and that’s fine.
>
> Can anyone tell me if this sounds like a problem upstream of Q8? Or maybe
> a problem with U7? Many thanks... Sure am glad to find this Elecraft
> reflector! David AC4BN
>

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Mike Morrow-3

Re: K1 VFO problem

In reply to this post by David L DuPuy

> K1 VFO PROBLEM: I’m building a K1, and have reached the mid-point on
> populating the RF board, at the Alignment and Test, Part I (page 36). All
> looks well until I get to VFO Range Test on p. 38, and I get E42 (VFO not
> functioning). The previous resistance and voltage checks were all fine.

That's this step:

"Tap MENU and locate CAL. To enable the operating
frequency calibration display (OPF), hold EDIT. The 100-Hz digit
should be flashing. (If you see E42, the VFO is not functioning.)"

FWIW, the VFO RF-Q8 can be functioning perfectly, yet the E42 message will
be generated if things are amiss at VFO BUFFER RF-Q9 or front panel board
COUNTER AMP FP-Q1. The latter is not too likely from what you've described,
but it's still something to keep in mind as you chase down the cause for
E42.

Mike / KK5F
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Tom Johnson

Re: K1 VFO problem

This post was updated on .

CONTENTS DELETED

The author has deleted this message.

Mike Morrow-3

Re: K1 VFO problem

In reply to this post by David L DuPuy

Tom,

You cite my name in your post, but I have absolutely no idea of what you refer. I built my K1 serial 175 in November 2000 and I experienced NO problems start to finish.

Quote the posting to which you refer, including its date.

Mike / KK5F

-----Original Message-----

>From: Tom Johnson <[hidden email]>
>Sent: Mar 23, 2019 9:03 PM
>
>I have exactly Mike Morrow's problem, and wonder if he ever got it resolved.
>Mike, if you are still around I'd like to hear what your resolution was.
>
>I am awaiting arrival of an RF Probe kit so I can do signal testing to
>attempt to trace down my problem. In the meantime I have looked over my
>board to the point it's invading my dreams, and I do not see any visible
>problem with the installation of any of the parts, with special attention
>to: Q9, Q1, R11, R12, L1, C2.
>
>I did see that I had not firmly seated U1, and corrected that: I was hoping
>that would do the trick, but it did not - still get the E42 code.
>
>It just seems to me that as everything tested out fine up until the
>installation of the L1 Toroid and the C2 capacitor (I'm using 68 pF disc for
>the 80 kHz range), that the issue should be centered there. I've confirmed
>the 33 turns on the toroid, and fiddled with the it's placement. I'm
>wondering if the winding direction makes a difference in the functioning of
>L1 - there is no picture of it in the manual, only a reference back to
>previous toroids, and I have wound it to match them. I've also confirmed
>continuity of the windings on L1.
>
>Lastly, I will reveal my testing ignorance here by mentioning my multimeter
>does measure frequency, but I am not sure if that applies in this case: ie,
>would that function as an RF Probe if I understood how to use it?
>
>I purchased my K1 18 years ago directly from Eric Schwartz when Elecraft was
>still quite young and I was active in the Santa Cruz County Amateur Radio
>Club. It is great to see how the company has grown and prospered! It wasn't
>until settling into retirement that I mustered up the courage to tackle
>building this project.
>
>If anyone has any theories on the K1 VFO failure issue other than those
>already offered, please clue me in.
>
>73,
>Tom Johnson
>KQ7TJ (formerly KQ6DV)

Don Wilhelm

Re: K1 VFO problem

In reply to this post by Tom Johnson

Tom,

Triple check C11 and C12 to be certain they are both 1200pF and that you
did not use the 120pF capacitor for one of them.

Build yourself an RF Probe. The schematic for one is shown in the K1
Manual Appendix on Troubleshooting. You can also purchase a kit from
Elecraft.

73,
Don W3FPR

On 3/23/2019 10:03 PM, Tom Johnson wrote:

> I have exactly Mike Morrow's problem, and wonder if he ever got it resolved.
> Mike, if you are still around I'd like to hear what your resolution was.
>
> I am awaiting arrival of an RF Probe kit so I can do signal testing to
> attempt to trace down my problem. In the meantime I have looked over my
> board to the point it's invading my dreams, and I do not see any visible
> problem with the installation of any of the parts, with special attention
> to: Q9, Q1, R11, R12, L1, C2.
>
> I did see that I had not firmly seated U1, and corrected that: I was hoping
> that would do the trick, but it did not - still get the E42 code.
>
> It just seems to me that as everything tested out fine up until the
> installation of the L1 Toroid and the C2 capacitor (I'm using 68 pF disc for
> the 80 kHz range), that the issue should be centered there. I've confirmed
> the 33 turns on the toroid, and fiddled with the it's placement. I'm
> wondering if the winding direction makes a difference in the functioning of
> L1 - there is no picture of it in the manual, only a reference back to
> previous toroids, and I have wound it to match them. I've also confirmed
> continuity of the windings on L1.
>
> Lastly, I will reveal my testing ignorance here by mentioning my multimeter
> does measure frequency, but I am not sure if that applies in this case: ie,
> would that function as an RF Probe if I understood how to use it?
>

Tom Johnson

Re: K1 VFO problem

In reply to this post by Mike Morrow-3

Sorry, Mike Morrow! The referred post was from David L DuPuy, March 04,
2013. I think you answered him and that's where I saw your name. I'm
obviously not adept at using the reflector - I just discovered there were a
string of replies to David I didn't read.

73

--
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Tom Johnson

Re: K1 VFO problem - RESOLVED

In reply to this post by Don Wilhelm

Thanks, Don Wilhelm, your intuition was correct: I installed a 120pF
capacitor at C12. When I replaced it with the correct 1200pF capacitor the
frequency display worked!

73,
Tom
KQ7TJ

Don Wilhelm wrote

> Tom,
>
> Triple check C11 and C12 to be certain they are both 1200pF and that you
> did not use the 120pF capacitor for one of them.
>
> Build yourself an RF Probe. The schematic for one is shown in the K1
> Manual Appendix on Troubleshooting. You can also purchase a kit from
> Elecraft.
>
> 73,
> Don W3FPR
>
> On 3/23/2019 10:03 PM, Tom Johnson wrote:
>
>> I am awaiting arrival of an RF Probe kit so I can do signal testing to
>> attempt to trace down my problem. In the meantime I have looked over my
>> board to the point it's invading my dreams, and I do not see any visible
>> problem with the installation of any of the parts, with special attention
>> to: Q9, Q1, R11, R12, L1, C2.
>>
>> I did see that I had not firmly seated U1, and corrected that: I was
>> hoping
>> that would do the trick, but it did not - still get the E42 code.
>>
>> It just seems to me that as everything tested out fine up until the
>> installation of the L1 Toroid and the C2 capacitor (I'm using 68 pF disc
>> for
>> the 80 kHz range), that the issue should be centered there. I've
>> confirmed
>> the 33 turns on the toroid, and fiddled with the it's placement. I'm
>> wondering if the winding direction makes a difference in the functioning
>> of
>> L1 - there is no picture of it in the manual, only a reference back to
>> previous toroids, and I have wound it to match them. I've also confirmed
>> continuity of the windings on L1.
>>
>> Lastly, I will reveal my testing ignorance here by mentioning my
>> multimeter
>> does measure frequency, but I am not sure if that applies in this case:
>> ie,
>> would that function as an RF Probe if I understood how to use it?
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:

> Elecraft@.qth

>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

--
Sent from: http://elecraft.365791.n2.nabble.com/
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