http://elecraft.85.s1.nabble.com/K2-100-Has-No-Output-on-80-or-40-When-Hot-tp5124474p5138119.html
from 20m down to 40 or 80. This cuts off the path through K14 and K13 to
> -----Original Message-----
> From: Don Wilhelm [mailto:
[hidden email]]
> Sent: Wednesday, June 02, 2010 5:50 PM
> To: Phil-W6TQG
> Cc:
[hidden email]
> Subject: Re: [Elecraft] K2/100 Has No Output on 80 or 40 When Hot
>
> Phil,
>
> The problem will be found in the VFO Range Selection area.
> Look at the
> schematic for the RF Board sheet 1.
> Check the soldering of C71 and C72 and relay K13.
> It is possible that when hot, the contacts of K13 (and
> possibly K14) are
> not making good contact.
> Set to 80 meters and wait until the failure occurs, then power the K2
> off and quickly (before things cool), check for continuity
> between K13
> pins 3 and 4 also between pins 7 and 8 - both should be zero
> ohms - if
> not, the relay has failed.
> Check K14 in a similar manner, but set to 40 meters - after
> the failure,
> you should have continuity between pins 3 and 4 of K14 and
> also between
> pins 7 and 8.
>
> The relay pins are numbered like an IC (pins 1 and 10 are at the same
> end). Look for the round solder pad at pin 1 (or the end
> with the white
> stripe).
>
> This is either a temperature related solder connection or a relay
> contact problem.
>
> 73,
> Don W3FPR
>
> Phil-W6TQG wrote:
> > Hi Don,
> >
> > Thank you for your help. Yes, it appears to be the VFO. The
> VCO readings
> > at TP1 for 20, 30, 40 and 80m are normal when the K2 is
> cool, but when
> > hot the readings are near 15,600 for 40 and 17,257 for 80.
> No wonder I
> > can't transmit or receive! 20 and 30m appear to be normal when hot.
> >
> > What do you suggest I look at next?
> >
> > 73,
> > Phil
> >
> >
> >
> >> -----Original Message-----
> >> From: Don Wilhelm [mailto:
[hidden email]]
> >> Sent: Tuesday, June 01, 2010 6:08 AM
> >> To: Phil-W6TQG
> >> Cc:
[hidden email]
> >> Subject: Re: [Elecraft] K2/100 Has No Output on 80 or 40 When Hot
> >>
> >> Phil,
> >>
> >> To use the base K2 BNC antenna jack, you must remove the
> >> KPA100 - if you
> >> attempt to use that jack, the load impedance between the base
> >> K2 and the
> >> KPA100 will not be correct, and "strange happenings" will
> be present.
> >>
> >> A total lack of power (yes, a display of 0.1 or 0.2 watts is
> >> actually no
> >> power out) is most likely a problem either in the bandpass
> >> filter or a
> >> problem with the VFO. Try the VFO first - set the frequency
> >> to the low
> >> end of the band and check the frequency with the counter
> probe in TP1
> >> using CAL FCTR - compare your frequency reading with the
> chart on the
> >> Schematic Key page. If you want to calculate the proper VFO
> >> frequency
> >> it should be within a few kHz of the frequency on the dial
> >> plus 4915 for
> >> bands below 15 meters.
> >>
> >> Check all the components in the bandpass filter area for 40m
> >> and for 80
> >> meters. On 40 meters, be certain C6 is properly installed
> >> between the
> >> two outer holes of the J15 position (the center hole
> should be empty).
> >>
> >> 73,
> >> Don W3FPR
> >>
> >> Phil-W6TQG wrote:
> >>
> >>> Every since the last Field Day, my K2/100 (#3713) loses
> >>>
> >> output, and the
> >>
> >>> receiver goes dead, on 40m and 80m when it gets hot. This
> occurs for
> >>> power levels of 9 watts and 100 watts. The 30m through 10m
> >>>
> >> bands are OK.
> >>
> >>> I can easily replicate the problem when the power amp is
> >>>
> >> connected, but
> >>
> >>> so far it seems to be OK when it is completely unplugged
> >>>
> >> from the K2.
> >>
> >>> Turning off the power amplifier through the Secondary Menu
> >>>
> >> does not make
> >>
> >>> a difference. While transmitting at 9W, the readings on the
> >>>
> >> display for
> >>
> >>> 40 and 80 are "0.1 1.01 - 1". With the power amplifier
> >>>
> >> connected to the
> >>
> >>> K2, I temporarily connected the antenna to J4 on the K2, so
> >>>
> >> that I could
> >>
> >>> bypass the power amplifier path. This did not help the dead
> >>>
> >> reception on
> >>
> >>> 40 or 80. I also tried connecting a dummy load through a
> >>>
> >> power meter to
> >>
> >>> J4 and transmitting at 9W. Again 40 and 80 didn't work but
> >>>
> >> the higher
> >>
> >>> bands were OK.
> >>>
> >>> I am assuming that the problem is in the LPF of the power
> >>>
> >> amplifier, but
> >>
> >>> am not sure 30m is OK, while 40 and 80 are not. Any hints would be
> >>> appreciated.
> >>>
> >>> 73,
> >>> Phil W6TQG
> >>>
> >>> ______________________________________________________________
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