[Elecraft] KPA-1500 failing on 160...AGAIN!

[Jim Miller]

Although the RMS voltage is pretty high. The peak voltage is higher
especially if SWR isn't 1:1 along the transmission line.

It could easily be above 1Kv and causing arcing.

73

jim ab3cv


On Fri, Sep 27, 2019 at 10:35 AM Michael Walker <va3mw at portcredit.net>
wrote:

> Like others have said
>
> Even though your analyzer says the antenna is ok, that is only one part.
> It can still be part of the problem at 1500 watts and if memory serves me
> well, that is about 275V (RMS) at 50 ohms.
>
> Something could be breaking down at that voltage so a good visual
> inspection would help.  Look for arcing at each connector, Ununs, Baluns,
> etc.
>
> Mike va3mw
>
> On Fri, Sep 27, 2019 at 9:18 AM Bob McGraw K4TAX <rmcgraw at blomand.net>
> wrote:
>
> >  Check for burn marks or carbon traces, both on the inside and outside,
> of
> > the SO-239 connectors.  These may look good with the antenna analyzer but
> > fail under power.
> >
> > I've also had PL-259's arc from center pin to shell on the inside. These
> > required removal/ disassembly of the coax in order to actually find the
> > fault.
> >
> > In all cases, once a flashover occurs, replacement of the connector is
> the
> > only solution.
> >
> > Bob, K4TAX
> >
> >
> > Sent from my iPhone
> >
> > > On Sep 27, 2019, at 6:00 AM, John Langdon <WOYB10051 at outlook.com>
> wrote:
> > >
> > > If it also happens with a dummy load, and the antenna analyzers shows
> > the same graph as before for R, X, then it is likely one of the
> connectors
> > between the KPA1500 output and the antenna. The one such problem I had
> was
> > old jumper I had put in to add an SWR bridge/monitor. It looked okay, and
> > was finger tight, but when I replaced it in an A/B test, the problem went
> > away.
> > >
> > > The other time, the antenna had changed its impedance curve, but was
> > still 'okay' and the tuner was trying to retune for it.
> > >
> > > 73 John N5CQ
> > >
> > >
> > > -----Original Message-----
> > > From: elecraft-bounces at mailman.qth.net <
> elecraft-bounces at mailman.qth.net>
> > On Behalf Of Jim Brown
> > > Sent: Friday, September 27, 2019 4:19 AM
> > > To: elecraft at mailman.qth.net
> > > Subject: Re: [Elecraft] KPA-1500 failing on 160...AGAIN!
> > >
> > >> On 9/26/2019 10:26 PM, Peter Dougherty wrote:
> > >> Any idea where to start looking here?
> > >
> > > And if it's a vertical, what about the radial system?
> > >
> > > 73, Jim K9YC
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