Re: N2WN: RE: 160M problem

[Julius Fazekas n2wn]

Hi Gary,
Just to let you know: I swapped out the power supply
and it cleared up the 160M problem.
Thanks again for the stellar support!
Julius
n2wn

--- Gary Surrency <[hidden email]> wrote:

> OK Julius. I hope you find that is all it is.
>
> Good luck!
>
> --
> 73, Gary AB7MY
> =========
> [hidden email]
> Elecraft Technical Support  
>  
>
>
>
> -----Original Message-----
> From: J F [mailto:[hidden email]]
> Sent: Monday, February 07, 2005 9:39 AM
> To: Gary Surrency
> Subject: Re: N2WN: RE: 160M problem
>
>
> Gary,
> Based on this list, I'm going to try #10. I do
> notice
> that the Power Supply seems to drop almost a volt in
> key down. So I suspect it at this junction. I do
> have
> another PS, so I'll try that first.
> Thanks again!
> Julius
> n2wn
>
> --- Gary Surrency <[hidden email]> wrote:
>
> > See what the TX current demand is with the power
> to
> > the KPA100 turned off,
> > so just the K2's QRP output is produced.
> >
> > Then try the K2 on 160m at max power without the
> > KPA100 connected at all.
> >
> > If the current demand is too high, it may be:
> >
> > 1) Wrong turns on the toroids in the lowpass
> filters
> > (LPF) for the K2 or
> > KPA100.
> > 2) Wrong or missing caps in the LPF for the K2 or
> > KPA100.
> > 3) Poor connections in these areas. Make sure all
> > toroids are well tinned
> > and soldered.
> > 4) Wrong freq. being produced, such as a kit I
> just
> > repaired that had no C75
> > installed in the VCO circuit for the K2. Check
> that
> > the freq. at TP1 is as
> > expected in the VCO Table in the K2 manual. The
> > freq. shown is with the VFO
> > at the bottom edge of the band. Check that the VCO
> > voltage is between 1.5
> > and 7.5VDC at 1800 and 2000kHz.
> > 5) Wrong turns on the PA output transformer of the
> > K2 or KPA100.
> > 6) Wrong caps in the PA input circuit between T1
> and
> > T2 on the KPA100.
> > 7) Lack of enough t-r switch reverse bias,
> resulting
> > in poor t-r switch
> > isolation and the result is oscillation of the
> > KPA100 PA stage. The left
> > side of the resistors at R11, R12 (nearest R14)
> must
> > be more than 100VDC
> > when in TX, and the higher the better.
> > 8) Apply the last two items of the attached KPA100
> > errata if the test in #7
> > above is not correct, or if your kit does not
> > already have these changes.
> > 9) Wrong toroid core used for SWR sensor T4. It
> must
> > be the larger FT50-37
> > gray core.
> > 10) Sometimes the power supply is the problem, and
> > it may be outputting a
> > poorly regulated voltage when the rig is operating
> > at high power on some
> > bands. A fellow in Holland last week had this
> > problem. Try another power
> > supply or 12V auto battery if this is suspected.
> >
> > --
> > 73, Gary AB7MY
> > =========
> > [hidden email]
> > Elecraft Technical Support
> >  
> >
> >
> >
> > -----Original Message-----
> > From: J F [mailto:[hidden email]]
> > Sent: Monday, February 07, 2005 7:13 AM
> > To: Gary Surrency
> > Subject: Re: N2WN: RE: 160M problem
> >
> >
> > Hi Gary,
> > I probably did not make the 30 seconds. I don't
> > recall
> > that being the same on the other bands, but I
> > probably
> > wasn't looking either.
> >
> > Cal Cur is set to 3.5. The only band (I checked
> this
> > weekend) that I get the high current warning on is
> > 160M. It looks like I draw 22 Amps with the pot
> > cranked, but I can back it off (almost 35%) and it
> > works fine. It does the same thing into a dummy
> > load.
> >
> > This was working fine previously. I'm not quite
> sure
> > what event caused the change. I guess what baffles
> > me
> > most, is that it is band specific. I would have
> > expected the problem to be in the circuitry you
> > mention, but accross all the bands... Curious eh?
> >
> > 73,
> > Julius
> > n2wn
> >  
> > --- Gary Surrency <[hidden email]> wrote:
> >
> > > Julius,
> > >
> > > The rig does not remember a frequency when it is
> > > turned off, unless 30
> > > seconds have elapsed or the mode or band has
> been
> > > changed. This saves write
> > > cycles to the 25LC320 EEPROM on the control
> board.
> > > See page 94 of the K2
> > > manual, "Backup Timer".
> > >
> > > CAL CUR should be set to 3.5A in the K2 menu to
> > > avoid unnecessary HI CUR
> > > warnings. If this occurs only when the K2 is
> > > operating without the KPA100
> > > 100w option, HI CUR may occur if the RF output
> > > exceeds 10w, the antenna load
> > > Z is not close to 50 ohms resistive, or if there
> > is
> > > an error on the 160m
> > > option such as the wrong number of turns on the
> > > lowpass filter toroids.
> > > Damage to U6 on the KPA100 can also prevent the
> > > needed VRFDET signal from
> > > the SWR detector to the K2 MCU VRFDET pin 2, as
> > can accidental
> > > incorrect connection of the ribbon or RS232
> > cables.
> > >
> > > If HI CUR occurs with the KPA100 installed and
> > > operating at 100w, then there
> > > could be a problem with the lowpass filters on
> it,
> > > such as the wrong turns
> > > count, wrong caps, or missing caps.
> > >
> > > Also:
> > >
> > > If the FWD and REFL cal pots on the KPA100 are
> not
> > > set accurately, it can
> > > cause too high or too low RF output. Most
> KPA100s
> > > have 41-44K from the wiper
> > > of the cal pots at R26 and R27 to ground when
> they
> > > are set correctly. This
> > > is more easily measured at the LM358 at U5 pin 5
> > > (FWD, R26), and U5 pin 3
> > > (REFL, R27).
> > >
> > > The 1N5711 diodes at D16, D17 in the SWR
> detector
> > on
> > > the KPA100 can
> > > definitely be damaged by nearby storms. Try
> > > operating the rig on all bands
> > > with a dummy load to see if the problem
> continues.
> > > Use care to not damage
> > > the rig from excessive RF output or current.
> > >
>

=== message truncated ===

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