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:[EMAIL PROTECTED]
> > Sent: Friday, January 12, 2007 11:39 PM
> > To: [EMAIL PROTECTED]
> > 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: [EMAIL PROTECTED]
> > > > [mailto:[EMAIL PROTECTED] Behalf Of David C Dawson
> > > > Sent: Friday, January 12, 2007 2:26 AM
> > > > To: elecraft@mailman.qth.net
> > > > 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
> > > > _______________________________________________
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> > > > --
> > > > 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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