[TenTec] Addendum: Troubleshooting linear amplifier
Bry Carling
af4k at hotmail.com
Thu Apr 14 07:05:03 EDT 2016
BTW -
The ONLY place that I see no change in the AA54 resonance readings, is when switching from 160m to 80m!
Bry AF4K
> From: af4k at hotmail.com
> To: ianmwilson73 at gmail.com; tentec at mailman.qth.net; tentec at yahoogroups.com
> Date: Tue, 12 Apr 2016 06:24:23 -0400
> Subject: Re: [TenTec] [Boatanchors] Troubleshooting linear amplifier
> CC: boatanchors at mailman.qth.net; flboatanchors at yahoogroups.com
>
> Update on the non-working Tentec 422 Cenurion...
>
> The best I can tell - there IS a difference in the tank when changing the bandswitch and the tune control.
> They appear to be working...
>
> I can look at the R and X values and see them change for different settings.
>
> I am using an AA-54 RigExpert analyzer connected via jumpers to th eoutput of the Loading cap (disconnected from the relay etc.) and scanning centered on 3.0 MHz and a range of 4.0 MHz.
>
> The crossover points for X from positive to negative moves considerably as I make band switch changes
> or vary the tuning capacitor.
> Looking at the main RFC in the plate circuit with one end disconnected and
> placing a B&K 875A capacitance / inductance meter across it, it takes a WHILE to settle.
> On the 2 mHz range, it reads
> 3.5 ohms DC
> 260 uH
>
> Does that seem normal? So I wonder if we are making any progress here!
>
> 73 & thanks to all who are helping with ideas.
>
> > From: af4k at hotmail.com
> > To: ianmwilson73 at gmail.com
> > Date: Tue, 12 Apr 2016 06:04:15 -0400
> > Subject: Re: [Boatanchors] Troubleshooting linear amplifier
> > CC: boatanchors at mailman.qth.net; flboatanchors at yahoogroups.com
> >
> > best I can deterine using GO there is a resonance only at 22.5 MHz regardless of where I set the
> > tuning caps or bandswitch. I tried jumpering across the bandswitch and nothing changes.
> > I
> > used both a GDO and also used an antenna analyzer coupled diretly to th
> > eoutput point, with everything else an and out of the PI network
> > disconnected.
> >
> > Rotating capacitors makes no difference.
> >
> > I have not connected a resistor yet.
> >
> > Bry AF4K
> >
> > Date: Mon, 11 Apr 2016 13:44:27 -0700
> > Subject: Re: [Boatanchors] Troubleshooting linear amplifier
> > From: ianmwilson73 at gmail.com
> > To: af4k at hotmail.com
> > CC: ranchorobbo at gmail.com; duvallddennis at gmail.com; boatanchors at mailman.qth.net; flboatanchors at yahoogroups.com
> >
> > Bry,
> > Disconnect the final plates, and connect a resistor of equivalent valueof the plate resistance of the driven finals from the plate side of the pi networkto ground. Looking into the output terminal with an antenna analyzer, you shouldnow see something like 50 ohms when the pi network is tuned up.
> > Please remember to disconnect all this - otherwise you will discover what MFJcharge to repair an antenna analyzer (1,2).
> > 73, ian K3IMW
> > 1: don't ask me how I know2: their rates are very reasonable and my MFJ-259B is as good as new now :)
> >
> > On Mon, Apr 11, 2016 at 1:30 PM, Bry Carling <af4k at hotmail.com> wrote:
> > Thanks. No, that is not it.
> >
> >
> >
> > The voltage and signals are switching the input network just fine. I have checked all of that thoroughly
> >
> > earlier. That is why I have drive on each band. The problem has something to do with non-resonance
> >
> > in the PI Network. The puzzle continues.
> >
> >
> >
> > > Date: Mon, 11 Apr 2016 08:51:23 -0500
> >
> > > Subject: Re: [Boatanchors] Troubleshooting linear amplifier
> >
> > > From: ranchorobbo at gmail.com
> >
> > > To: duvallddennis at gmail.com
> >
> > > CC: af4k at hotmail.com; Boatanchors at mailman.qth.net
> >
> > >
> >
> > > The Centurion bandswitch has two wafers. One switches both pi network
> >
> > > fixed load caps and pi output coil taps. The other is actually a
> >
> > > small pc card mounted on the switch (I don't remember exactly) that is
> >
> > > made to switch input network relays. There is a pc card with separate
> >
> > > input matching networks for each band and relays that open and close,
> >
> > > a pair for each band so the correct network is in line for the
> >
> > > selected band. The little board on the bandswitch has a ribbon cable
> >
> > > to the input network card. if the amp isn't working on any band the
> >
> > > bandswitch is probably okay. Perhaps the 24 v. supply to the input
> >
> > > network board that powers the relays is out. That would mean no
> >
> > > relays or LEDs or anything else work. The filament supply transformer
> >
> > > has a tertiary winding to provide the ac that is rectified to get the
> >
> > > 24 v. filtered dc.
> >
> > >
> >
> > >
> >
> > > Sounds like you have your exciter connected to the antenna jack and
> >
> > > the antenna feedline connected to the exciter input jack.
> >
> > >
> >
> > > Rob
> >
> > > K5UJ
> >
> >
> >
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