There were several vintages of the commander hf-2500 and along the line he
raised the plate voltage. The older ones I have only start at about 2kv on
the plate, the new ones are about 2.7kv. And yes the HV does drop quite a
bit, the newer ones drop to about 2.2kv if I remember right at 1500w out.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Patrick Egloff
> Sent: Sunday, December 07, 2008 06:36
> To: amps@contesting.com
> Subject: [Amps] Fwd: rx noise?
>
> Hi All,
> I also have an HF2500 amplifier i got second hand years ago.
>
> During the last CQWW CW i had problem with the antenna switching relay. I
> had to open the amp an try to clean this nasty relay.... I did it twice,
> in
> the middle of the battle ! I must change this low quality relay !
>
> My question concerns the HV drop. On my amplifier, the voltage drops a
> lot,
> i can't remember how much but i always thought it was too.
>
> The output power is never over 1300W.
>
> So, my question. How much R power should this amplifier deliver and how
> much HV does it have under load and no load ?
>
> 73, Patrick
>
>
> 2008/12/7 W7RY <w7ry@arrl.net>
>
> I would suspect the HV diodes rather than the filter caps. You did say
> there
> > was plate voltage fluctuations?
> >
> > 73
> > Jim W7RY
> >
> > ----- Original Message -----
> > From: David Robbins K1TTT
> > To: 'Amps'
> > Sent: Saturday, December 06, 2008 3:46 PM
> > Subject: Re: [Amps] rx noise?
> >
> >
> > I really, REALLY hate intermittent problems like this... it wouldn't do
> it
> > cold. So I started warming it up, after 1/2 hour or so I got the
> > transformer up to 225f, the rf deck surface about 150f, the tubes about
> > 130f, the case was nice and toasty... and I got about 15 seconds of
> noise
> > from all of that. It may have been modulated a bit by line voltage
> > fluctuations from the 160m contest op on the next station, but wasn't
> > dependent on it. There was no measurable grid or plate current when it
> > did
> > it. I did get to cycle the stby/op switch a couple times and the noise
> > dropped but didn't go away when I went to stby... so perhaps it could
> be
> > something in the control board oscillating when it hits some particular
> > temperature, but its darn hard to reproduce.
> >
> >
> > David Robbins K1TTT
> > e-mail: mailto:k1ttt@arrl.net
> > web: http://www.k1ttt.net
> > AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> >
> >
> > > -----Original Message-----
> > > From: Joe Subich, W4TV [mailto:w4tv@subich.com]
> > > Sent: Saturday, December 06, 2008 18:54
> > > To: 'K1TTT'
> > > Cc: 'Amps'
> > > Subject: RE: [Amps] rx noise?
> > >
> > >
> > > Check the bias switch (relay, transistor, ?). If cutoff is
> > > not being applied in receive, the tube will generate wideband
> > > noise ("shot" noise).
> > >
> > > 73,
> > >
> > > ... Joe, W4TV
> > >
> > >
> > > > -----Original Message-----
> > > > From: amps-bounces@contesting.com
> > > > [mailto:amps-bounces@contesting.com] On Behalf Of Paul Kraemer
> > > > Sent: Saturday, December 06, 2008 12:57 PM
> > > > To: n8de@thepoint.net; K1TTT
> > > > Cc: Amps
> > > > Subject: Re: [Amps] rx noise?
> > > >
> > > >
> > > > How about from a zener diode in a bias supply.
> > > > They make dandy noise generators and were the source of
> > > > widband rf for the
> > > > old Omega noise bridge. The current to make noise is
> > > > critical, line voltage
> > > > upset could put it at that point?
> > > > Just fuel for thought.
> > > > Paul K0UYA
> > > > ----- Original Message -----
> > > > From: <n8de@thepoint.net>
> > > > To: "K1TTT" <K1TTT@ARRL.NET>
> > > > Cc: "Amps" <amps@contesting.com>
> > > > Sent: Saturday, December 06, 2008 11:24 AM
> > > > Subject: Re: [Amps] rx noise?
> > > >
> > > >
> > > > > Dave,
> > > > > Sounds like a leaky power supply capacitor. Might be a cold
> solder
> > > > > joint in the capacitor chain. Good luck
> > > > > Don
> > > > > N8DE
> > > > >
> > > > > Quoting K1TTT <K1TTT@ARRL.NET>:
> > > > >
> > > > >> I have a commander hf-2500 (pair of 3cx800a7's, no qsk)
> > > > that seems to
> > > > >> be working fine. However, during cqww cw last week I had
> > > > to pull it
> > > > >> off the 20m station because it was making a broadband
> > > > noise while on
> > > > >> receive. I put it back on the station today and it isn't doing
> it
> > > > >> now. I tried warming it
> > > > >> up a bit and it still didn't do it....though its obviously
> > > > not as warmed
> > > > >> through as after 40 or so hours of cqww. The only other
> > > > thing I noticed
> > > > >> is
> > > > >> when it was doing it the plate voltage dropped a bit,
> > > > maybe 50-100v, but
> > > > >> I'm
> > > > >> not sure if that was a cause or effect since the line
> > > > voltage sag from
> > > > >> the
> > > > >> other stations can make the hv sag a bit here. Any ideas
> > > > where to start
> > > > >> looking??
> > > > >>
> > > > >>
> > > > >> David Robbins K1TTT
> > > > >> e-mail: mailto:k1ttt@arrl.net
> > > > >> web: http://www.k1ttt.net
> > > > >> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> > > > >>
> > > > >>
> > > > >>
> > > > >>
> > > > >> _______________________________________________
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> > > > >
> > > > >
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>
>
> --
> Patrick Egloff - TK5EP
> email : pegloff@gmail.com
> Web page : http://tk5ep.free.fr
>
>
>
> --
> Patrick Egloff - TK5EP
> email : pegloff@gmail.com
> Web page : http://tk5ep.free.fr
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