[TenTec] Argosy 2

Wed Oct 7 16:21:31 EDT 2020

"  i see a varying voltage on U1 when i rotate R2," and you can also see
the final bias voltage at L3 (which you have set to 0.7 Volts) change as
you adjust R2? And as you do that you see no current through L5 ( the final
collector current ) changing along with the R2 setting? If that is the case
either the finals are bad or somewhere there is an open circuit. Are R12
and R15 okay?

N6KB

On Wed, Oct 7, 2020 at 9:58 AM ROLAND HOWELL via TenTec <
tentec at contesting.com> wrote:

>
> Good Evening Ken
>
> Ok i will answer as many of your questions as i can:
>
> 1st: all semiconductors ( 3 x legged fuses hi hi) have been changed as
> has U1. The radio was sold to me as working complete, but when i opened
> it up to see why no RF, no PA module, i found one on a web site and
> purchased it, not knowing its parentage i did what i thought was the
> sensible thing and changed everything, as items removed and tested all
> found to be toast.
>
> 2nd: my pig tail arrangement is purely a short length of co-ax with a
> pl259 fitted, this was stuck onto the collectors of the drivers leaving
> T2 and T3 in circuit, so you are right the drivers are working.
>
> 3rd: I managed to set the bias for the drivers at exactly 30Ma,
> surprised myself with that. i then tried to do the same with the finals,
> nothing, i do have 0.7v (as per Mick advice) on the finals,
> I tested all devices before installing them and tried to match them as
> close as possible, unfortunately it is difficult to determine if the
> finals are genuine or the notorious chinese copies, they looked ok!.
>
> 4th: i see a varying voltage on U1 when i rotate R2, i had purchased 17
> yes 17 transistors ( the 1st 12 all turned out to be faulty, yet NOS!)
> so i purchased another 5 from a good supplier, 4 out of the 5 tested
> faulty, just 1 tested ok, they want those back so i cant use the only
> good one. I used a new equivalent in its place, still no joy. so every
> possibility the finals are gone.
>
> Hope that covered all you questions and Ken don't worry about asking me
> to repeat things as i am at my wits end with this radio.
>
> regards
>
> 73
>
> Snowy
>
> ------ Original Message ------
> From: "Ken Brown" <kenradiobrown at gmail.com>
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Sent: Wednesday, 7 Oct, 20 At 20:23
> Subject: Re: [TenTec] Argosy 2
> 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 at 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 at 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 at 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 at gmail.com>
> To: "Discussion of Ten-Tec Equipment" <tentec at 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 at 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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