K2 #05386 has developed a problem

[David C Dawson-2]

Hi,
My K2, recently completed, has developed a 'howl' on the 14MHz band.

I had finished the rig and got it tweaked and performing very well,
even making a contact with K6STA on 20 meters (He gave me 579)

I then constructed the KIO2 and got it working with my logging program
(tlf).

The KIO2 began to malfunction, so I took it out and re-did the wiring on
the aux board.

I replaced it and it seemed to be fine except for a brief glitch.

Then I noticed that there was a 'howl' all across the 14MHz band, but
not on any other band.

I removed the KIO2 and set up the rig. The howl was still there, exactly
as before.

What could have happened?

I noticed that touching the leads of R24 or R25 modified the noise, but
that's about what I know.

The noise covers the whole band as far as I tuned.

Anybody got a suggestion for how I should start troubleshooting?
Thanks
--
David Dawson
 
People of privilege will always risk their complete destruction
rather than surrender any material part of their advantage.
                -- John Kenneth Galbraith
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[Don Wilhelm-3]

David,

Actually the 'where to start' question does not have a good answer from your
description.  The problem characteristics have to be better defined before
plunging in and actually doing anything physical to the K2 (i.e. you don't
want to 'fix' things that are not broken).

Since you get a change in the howl pitch when touching R24 and R25, it would
be wise to first verify the PLL/VCO signal.  If you have a general coverage
receiver, tune it around the 20 meter VFO frequency (about Dial frequency
plus 4915 kHz - or 18915 when tuned to 14000) and observe what the VCO
signal sounds like.  If you cannot obtain a strong enough signal, by
dropping an antenna wire to the GC rcvr into the K2, you stick a wire into
TP1 to serve as a short antenna.

Everyone has a differnt definition for 'howl' in their minds, so if you can
be a bit more descriptive about the sound it may be helpful.  Is it only
receive, or is it present in the transmitted signal?  How loud is it?  Could
it possibly be a noise originating outside the K2?  Do you hear it with the
antenna disconnected?

Tell us what tools you have available there - frequency counter,
'oscilliscope, etc.

73,
Don W3FPR

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]]On Behalf Of David C Dawson
> Sent: Friday, January 12, 2007 2:26 AM
> To: [hidden email]
> Subject: [Elecraft] K2 #05386 has developed a problem
>
>
> Hi,
> My K2, recently completed, has developed a 'howl' on the 14MHz band.
>
> I had finished the rig and got it tweaked and performing very well,
> even making a contact with K6STA on 20 meters (He gave me 579)
>
> I then constructed the KIO2 and got it working with my logging program
> (tlf).
>
> The KIO2 began to malfunction, so I took it out and re-did the wiring on
> the aux board.
>
> I replaced it and it seemed to be fine except for a brief glitch.
>
> Then I noticed that there was a 'howl' all across the 14MHz band, but
> not on any other band.
>
> I removed the KIO2 and set up the rig. The howl was still there, exactly
> as before.
>
> What could have happened?
>
> I noticed that touching the leads of R24 or R25 modified the noise, but
> that's about what I know.
>
> The noise covers the whole band as far as I tuned.
>
> Anybody got a suggestion for how I should start troubleshooting?
> Thanks
> --
> David Dawson
>
> People of privilege will always risk their complete destruction
> rather than surrender any material part of their advantage.
>                 -- John Kenneth Galbraith
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.16.9/622 - Release Date:
> 1/10/2007 2:52 PM
>

--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.16.9/622 - Release Date: 1/10/2007
2:52 PM

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[David C Dawson-2]

Notes to all concerned:
Following on from before,
I probed the 'howl' down to 4.34 MHz, below which it was not audible,
and found the signal strongest near K15. This signal is less strong than
the signal at 18.915 MHz
--
David Dawson
 
People of privilege will always risk their complete destruction
rather than surrender any material part of their advantage.
                -- John Kenneth Galbraith
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[David C Dawson-2]

Hi,
On Fri, Jan 12, 2007 at 11:50:22PM -0500, Don Wilhelm wrote:
> David,
>
> It does rather confirm that the VCO signal is giving you the problem.
>
> Make a continuity check of RFC15 on the bottom of the RF Board - You may
> find it open.  If it is open, place a short around it and see if the VCO
> signal improves, if it does, put a new RF Choke in place of RFC15.
RFC15 shows about 8 or 9 ohms, I'm assuming that means it is OK.

>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> > From: David C Dawson [mailto:[hidden email]]
> > Sent: Friday, January 12, 2007 11:39 PM
> > To: [hidden email]
> > Subject: Re: [Elecraft] K2 #05386 has developed a problem
> >
> >
> > Thanks Don,
> > On Fri, Jan 12, 2007 at 07:47:11AM -0500, Don Wilhelm wrote:
> > > David,
> > >
> > > Actually the 'where to start' question does not have a good
> > answer from your
> > > description.  The problem characteristics have to be better
> > defined before
> > > plunging in and actually doing anything physical to the K2
> > (i.e. you don't
> > > want to 'fix' things that are not broken).
> > >
> > > Since you get a change in the howl pitch when touching R24 and
> > R25, it would
> > > be wise to first verify the PLL/VCO signal.  If you have a
> > general coverage
> > > receiver, tune it around the 20 meter VFO frequency (about Dial
> > frequency
> > > plus 4915 kHz - or 18915 when tuned to 14000) and observe what the VCO
> > > signal sounds like.  If you cannot obtain a strong enough signal, by
> > > dropping an antenna wire to the GC rcvr into the K2, you stick
> > a wire into
> > > TP1 to serve as a short antenna.
> > >
> > > Everyone has a differnt definition for 'howl' in their minds,
> > so if you can
> > > be a bit more descriptive about the sound it may be helpful.  Is it only
> > > receive, or is it present in the transmitted signal?  How loud
> > is it?  Could
> > > it possibly be a noise originating outside the K2?  Do you hear
> > it with the
> > > antenna disconnected?
> > >
> > > Tell us what tools you have available there - frequency counter,
> > > 'oscilliscope, etc.
> > The summary is this:
> > I have a AOR 1500 scanner which receives from 500kHz to 1.3GHz and will
> > receive FM and AM and has a BFO.
> >
> > With a duckie attached to the scanner I was able to listen to 18915 with
> > the K2 tuned to 14000 kHz. I found the signal strong all over the
> > front-left quadrant of the RF board. The signal is, I believe, a square
> > wave with some modulation.
> >
> > The VCO signal sounded much like what the receiver hears. I believe it
> > is the same signal, in fact.
> >
> > It is a lound signal, possibly over half as loud as the K2 can put out
> > through the speaker
> >
> > I think it could not be transmitted as the rig has no SSB board, but I
> > heard nothing when I tried anyway.
> >
> > I have only a digital multimeter and an RF voltage probe and the
> > scanner. Possibly I could borrow some equipment if necessary.
> >
> > The signal is audible with or without the antenna connected. It
> > _definitely_ is not a signal originating outside the K2. In fact I sat
> > the K2 on top of my Icom 730 and tuned to the same frequency as on the
> > K2 and the Icom could not hear it (and the Icom is working pretty well
> > at present, although showing its age a tiny bit).
> > >
> > > 73,
> > > Don W3FPR
> > >
> > > > -----Original Message-----
> > > > From: [hidden email]
> > > > [mailto:[hidden email]]On Behalf Of David C Dawson
> > > > Sent: Friday, January 12, 2007 2:26 AM
> > > > To: [hidden email]
> > > > Subject: [Elecraft] K2 #05386 has developed a problem
> > > >
> > > >
> > > > Hi,
> > > > My K2, recently completed, has developed a 'howl' on the 14MHz band.
> > > >
> > > > I had finished the rig and got it tweaked and performing very well,
> > > > even making a contact with K6STA on 20 meters (He gave me 579)
> > > >
> > > > I then constructed the KIO2 and got it working with my logging program
> > > > (tlf).
> > > >
> > > > The KIO2 began to malfunction, so I took it out and re-did
> > the wiring on
> > > > the aux board.
> > > >
> > > > I replaced it and it seemed to be fine except for a brief glitch.
> > > >
> > > > Then I noticed that there was a 'howl' all across the 14MHz band, but
> > > > not on any other band.
> > > >
> > > > I removed the KIO2 and set up the rig. The howl was still
> > there, exactly
> > > > as before.
> > > >
> > > > What could have happened?
> > > >
> > > > I noticed that touching the leads of R24 or R25 modified the
> > noise, but
> > > > that's about what I know.
> > > >
> > > > The noise covers the whole band as far as I tuned.
> > > >
> > > > Anybody got a suggestion for how I should start troubleshooting?
> > > > Thanks
> > > > --
> > > > David Dawson
> > > >
> > > > People of privilege will always risk their complete destruction
> > > > rather than surrender any material part of their advantage.
> > > >                 -- John Kenneth Galbraith
> > > > _______________________________________________
> > > > Elecraft mailing list
> > > > Post to: [hidden email]
> > > > You must be a subscriber to post to the list.
> > > > Subscriber Info (Addr. Change, sub, unsub etc.):
> > > >  http://mailman.qth.net/mailman/listinfo/elecraft
> > > >
> > > > Help: http://mailman.qth.net/subscribers.htm
> > > > Elecraft web page: http://www.elecraft.com
> > > >
> > > > --
> > > > No virus found in this incoming message.
> > > > Checked by AVG Free Edition.
> > > > Version: 7.5.432 / Virus Database: 268.16.9/622 - Release Date:
> > > > 1/10/2007 2:52 PM
> > > >
> > > --
> > > No virus found in this outgoing message.
> > > Checked by AVG Free Edition.
> > > Version: 7.5.432 / Virus Database: 268.16.9/622 - Release Date:
> > 1/10/2007
> > > 2:52 PM
> > >
> >
> > --
> > David Dawson
> >
> > People of privilege will always risk their complete destruction
> > rather than surrender any material part of their advantage.
> >                 -- John Kenneth Galbraith
> > --
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.5.432 / Virus Database: 268.16.10/624 - Release Date:
> > 1/12/2007 2:04 PM
> >
> --
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.16.10/624 - Release Date: 1/12/2007
> 2:04 PM
>

--
David Dawson
 
People of privilege will always risk their complete destruction
rather than surrender any material part of their advantage.
                -- John Kenneth Galbraith
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[David C Dawson-2]

Don,
I misunderstood your question about the 'howl' being present on
transmit, I think. Sorry about that.

I'd checked the choke you mentioned and when the penny dropped,
regarding transmit, I put the rig back together and lo and behold,
it seems to be back to normal. I speculate that a piece of junk got in
somewhere and shorted out something, until I disasembled and put
together the rig again.

I don't know if this is the end of the story, I hope so.
Thanks all. So far so good now.
--
David Dawson VE7HP
 
People of privilege will always risk their complete destruction
rather than surrender any material part of their advantage.
                -- John Kenneth Galbraith
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