The plate voltage fluctuations are from line sag from another amp running
the 160m contest. I couldn't sort that out last week with the m/m
operation, but yesterday's test showed that the noise occurred independent
of the hv fluctuation, it may have modulated it a bit but wasn't completely
correlated with it.
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 W7RY
> Sent: Sunday, December 07, 2008 05:26
> To: 'Amps'
> Subject: Re: [Amps] rx noise?
>
> 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
> > > >>
> > > >>
> > > >>
> > > >>
> > > >> _______________________________________________
> > > >> Amps mailing list
> > > >> Amps@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/amps
> > > >>
> > > >
> > > >
> > > >
> > > > _______________________________________________
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> >
>
>
>
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