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@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@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@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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