Hi Snowy,
I guess I don't know exactly what your pig tail setup is. When you
connect to the collectors of the drivers do you mean you have your leads
paralleled across the primary windings of T3 loading the drivers with your
pigtail setup AND T3 simultaneously? Or are you disconnecting the T3
primary, and loading the collectors of the drivers only with your pig tail
setup? I guess at this point that is not really important since the power
levels you are measuring there are reasonable and confirm that the drivers
are working.
I think I would have kept the T3 primary connected to the collectors
of the driver transistor and disconnected to secondary of T3 and connected
my wattmeter to the secondary of T3, without it also connected to the bases
of the finals. Maybe disconnecting L3 to remove the DC bias in case that
would have some undesirable effect on your wattmeter.. You could just
connect the output right there and run QRP without the finals.
I have not been following this discussion real carefully, so please
excuse me if I ask questions you have already been over. Have you put a
milliammeter in series with L5 to measure the PA final current
independently of the driver current? If the bias circuit and the final
transistors are good you should be able to adjust R2 and see the current go
up and down when in TX mode, and go to near zero when not in TX mode. If
you can see the bias voltage at emitter of Q5 going up and down when
adjusting R2, but you don't see the final collector current going up and
down that would be an indication that the finals are toast.
If on the other hand you do not see the bias voltage measured at Q5
emitter change as you adjust R2, and also switch on and off with TX and not
TX, then the final bias supply circuitry is not working. (Another
possibility is that the final base to emitter junctions are blown up and
presenting a near short circuit to the bias supply) Then you would want to
confirm that D1, D3, U1 and Q5 are all working. Starting at D1 you want to
see 5.6 Volts there when in TX mode. R2 should be able to set the voltage
at pin 3 of U1 from a minimum of whatever D3's forward voltage is ( about
0.6 or 0.7 volts I think ) and some slightly higher level like about 0.2
Volts higher (based on voltage divider formed by R6, R7 and R2)
Maybe you've already been through all that. If so sorry for being
repetitive. Hope I have been helpful.
Ken N6KB
On Wed, Oct 7, 2020 at 5:02 AM Mike Bryce <prosolar@sssnet.com> wrote:
> Roland,
>
> unless someone upgraded the argosy II, they didn’t come from the factory
> with 17 and 24 meters. They did do 30 meters out of the box
>
> Mike, WB8VGE
> www.theheathkitshop.com
>
>
>
> > On Oct 6, 2020, at 6:35 PM, Ken Brown <kenradiobrown@gmail.com> wrote:
> >
> > "I have also noticed that there is very little output on a number of
> > bands,(10m, 17m, and a couple of others, possible fault on the filter?)."
> >
> > You mean TX RF output from the drivers? And the output from the finals is
> > low on all bands?
> >
> > On Tue, Oct 6, 2020 at 10:24 AM ROLAND HOWELL via TenTec <
> > tentec@contesting.com> wrote:
> >
> >>
> >> Hi Ken
> >>
> >> As per Mikes advice i have checked the voltages to the final's ( 0.7v)
> >> all ok, not certain of the function of Q5 and U1.
> >>
> >> Have replaced all of the driver's, final's and U1.
> >>
> >> Have checked the output on my scope, nice and healthy input and output
> >> from the drivers, it gets lost from then on.
> >>
> >> I have also noticed that there is very little output on a number of
> >> bands,(10m, 17m, and a couple of others, possible fault on the filter?).
> >>
> >> I purchased a scruffy but working radio to take voltage comparisons as i
> >> have 6.1volts on the t/rx connector #8 on the rf mixer board whilst in
> >> receive, disconnect the tx power to #8, rx audio comes up a few dBs,
> >> Both Mike and i think that the radio has been zapped, yet the rx is
> >> great.
> >>
> >> hope i haven't bored you
> >>
> >> 73
> >>
> >> Snowy
> >>
> >> ------ Original Message ------
> >> From: "Ken Brown" <kenradiobrown@gmail.com>
> >> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> >> Sent: Tuesday, 6 Oct, 20 At 20:40
> >> Subject: Re: [TenTec] Argosy 2
> >> Since I don't have a schematic for that radio to look at I'm not sure
> >> where
> >> T3 is. Input to final transistors or output? Even so, direct comparison
> >> on
> >> a wattmeter may be misleading. The impedance is different in various
> >> places
> >> in the PA circuit, only the input and output to the whole PA board can
> >> be
> >> assumed to be 50 Ohms. How about measuring voltage at those various
> >> points
> >> using either a HF AC Voltmeter (the kind with the detector diode right
> >> inside the probe) or an Oscilloscope with 10X probe?
> >> DE N6KB
> >> On Tue, Oct 6, 2020 at 9:21 AM ROLAND HOWELL via TenTec <
> >> tentec@contesting.com> wrote:
> >>
> >> Hi All
> >> Update on the above radio, i attached a co-ax pigtail to the collectors
> >> of the drive trannies, got 1.5 - 2 watts out at that point, then fitted
> >> the pig tail to the base's of the power trannies, got just milliwatts
> >> out, so then attached the pig tail's to output leads of the T3, got just
> >> 0.5watts out of that transformer.
> >> So do those transformers go faulty?
> >> Any/all advice appreciated
> >> Thanks
> >> Snowy G0HZE
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