[ARC5] T-22 Woes

[Ian Wilson]

There doesn't seem to be anything left except the path from
the plates to the tank coil / variable coupling whatsit, and of
course the connections to the roller inductor.

I don't recall whether Mark has a 'scope. If so, should be able
to use a small (5pF 1kV or so) capacitor to follow the RF from
the plate caps to where it disappears.

Do be careful, it is very easy to become focussed on the
debugging and forget about the lethal voltages. Turn PSU off,
connect probe, step back, turn PSU on, repeat.

73, ian K3IMW



On Tue, Jun 11, 2013 at 3:36 PM, Mark K3MSB <mark.k3msb at gmail.com> wrote:

> Thanks for the reply guys.
>
> I was measuring the plate voltages on the tube anodes.  This tells me RL-50
> & RL-51 (the suppressors), R-76, and L-53 are OK.
>
> I replaced C-72 which didn't help.
>
> I did zorch my relay in the power supply (it's the one from the modulator
> unit) so I'm having to work at lower plate voltages until I can get a
> suitable replacement relay.   I'm not using the keying and voltage divider
> network as per Dave's article (and the manual).
>
> As an aside, there is very little chirp on my 80M T-19 with it being keyed
> as per the manual.
>
> I now have good screen voltage.  Don't ask me why.   I did go around and
> resolder joints  after that happened.
>
> Before the relay went and I was running about 550V on the plates,  I was
> getting 320V on the screens and about -45 to -50 on the grids.  Nothing on
> the output.
>
> Noe that I'm using a temporary relay I'm running with 350V on the plates.
> This gives me   -25 on the grids,  225 on the screens, and an Ip of 130
> mA.  No output.
>
> If I'm getting good voltages on the grid,  that's telling me I'm developing
> sufficient drive from the oscillator (across R-74).
>
> If I'm getting good grid, screen and plate voltages, drawing 130 mA of Ip,
> and I replace just about all the parts from the tubes to the
> output..........What is left to replace?   I'd pull some hair out but I
> have little enough as it is.
>
> 73 Mark K3MSB
>
>
>
>
>
>
>
> On Tue, Jun 11, 2013 at 5:18 PM, <WA5CAB at cs.com> wrote:
>
> > A likely culprit for this would be the two parasitic suppressors inside
> the
> > plate tank coil.
> >
> > In a message dated 06/11/2013 15:44:53 PM Central Daylight Time,
> > kgordon2006 at frontier.com writes:
> > > Mark: I still suspect that your plate voltage is "missing". Where did
> you
> > >
> > > measure this? If not directly at the tube plate connection, it still
> may
> > > be
> > > missing.
> > >
> > > One thing that makes me suspect this is that your screen voltage is
> low,
> > > which indicates excessive current draw, which usually only takes place
> > > when
> > > the plate voltage is missing.
> > >
> > > It is certainly possible that the RF connection between the plates and
> > the
> > >
> > > tuning network is also open, but that seems to be less likely.
> > >
> > > Ken W7EKB
> > >
> >
> > Robert Downs - Houston
> > wa5cab dot com (Web Store)
> > MVPA 9480
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