|Ten Tec Argonaut 505 - the first Argonaut that Ten Tec brought out in 1974 (I'm going by memory
here). Some pictures and discussion as I go over this unit that needs some TLC. It is not receiving
or transmitting. -- Update notes (April 2012) ..replaced control board, driver transistor and finals. A
step by step trouble shooting analysis in this article that applies to other radios as well.
Typical Trouble shooting strategy: A visual inspection first. Look the unit over for any irregularities. Note worthy right off the bat..I noticed on the
control board..where the reed relay is located..there was a diode that was soldered in to "probably try and fix a problem". So...The control board will
be checked over with my V.O.M and the Ten Tec 505 voltage charts in the manual. A DC check is always done first in the stages of trouble shooting. If
the DC voltages are not right then..the situation must be dealt with first. It is February 20th 2012 and still dead of winter up here in North-Eastern
Ontario Canada. I have been doing alot of inventory on my small electronics parts collection and I have been doing the odd job for people that they
send me in the mail..but now I have some free time to do some trouble shooting on my own collection of gear. I buy broken rigs and try to fix them or
..if they are quite far gone and the chasis is damaged/holes drilled in it..(I have 2 HW7s and an old Ten Tec PM2 that are in this condition..I will part
them out. People have written me for small items like the slug in one of the PM2 coils and I do small wee jobs like that for only $10/hr or even less for
something like that particular slug.
Here is the control board. I took out the corner
screws and will be removing the board to
replace or at least clean up the blue diode that
is left of the reed relay.
It was a bad looking sloppy replacement with a
blob of solder.
Sometimes these reed relays malfunction. I had
one (back in 1974 when I bought my first
Argonaut 505 from a dealer in Toronto area) that
the reed relay would not switch over from
Transmit to receive for some reason. The dealer
sent me a whole new board for it. that was only
about a month into its lifetime.
This particular control board pictured left..is
faulty. I will be trouble shooting this particular
board (later this year 2012). For now..I had
another control board with reed relay to
substitute in to the radio. \
When I go through the trouble shooting process
..I will be adding it on to this article on the 505
so you can check back later. (noted 23 Mar 2012.)
9 mhz crystal filter board.
NOTE the CA3053 RCA IC. These
are not hard to buy from Ebay for
about $15.00 or so.
A bit pricey. They may be similar or
same as a CA3028..Id have to verify
that. The CA3028 is far less to buy.
I have only one spare CA3053. I
would like to buy a bunch if I could
get them at a reasonable price.
$15 is too much for me to resell
them at any sort of reasonable
The audio board. Note the use of substitute transistors.
This was a temporary "fix" The transistors do not have any
heat sink at the moment.
These transistors are not the original transistors. These
are substitute ones and they do not have the rectangular
body that can be fastened down to a heatsink. This is a
'temporary fix" until I find the right ones. I will be shopping
flea markets for old transistors this year again.
Later (on page 4 of this article)..I modify some heatsinks for
these transistors. Aftermarket types of these germanium
transistors are available from NTE. Ten Tec probably sells
them as well. I know one qrper (VE3DJX SK) who replaced
them with Silicon transistors in his old 505. That might do
as a temporary fix. The later series of Argonauts 509 and
515 did away with this "complementary pair" of germanium
This will have to be taken care of.
NOTE: March 4th..I did some operating with the Argonaut
505 last night. Was listening to myself on my FT757GX while
I was calling cq on the low end of 80 meters.
The RF final PA transistors and associated heat sink.
Getting at this PA circuit board requires taking off the front
I did (eventually find) that both PA transistors of this 505
were damaged and needed replacement.
If you keep going through this multi-page article (follow the
blue lettered links) you will see how I started experimenting
with different transistors ie MRF237s, MRF8004s,2n2219as,
I also had to replace the driver transistor a 2n4427. I sell
spare parts for the Argonaut 505, 509 and 515.
My supply of 2n4427s is quite low at the moment..so I
substituted an MRF607 which seemed to be a close enough
match in characteristics and it seems to be working quite
well. (noted: 4 March 2012).
|I started off with NO TRANSMIT or receive. I decided to switch control boards as I had one that is the same brown color and I thought maybe it actually
belongs with this Argonaut 505. So I switched boards. Now I have receive but the transmit signal is very weak. I decide to trace the circuit through with
starting with the new control board. I drew a sketch..see below. This is in receive mode and the voltages seem good. The radio works on receive now.
The good working control board..looks the same as the other boards..I think they are
phenolic boards where as the other board that doesnt work..looks like a higher grade
board made from fiberglass. The circuit below is the good control board voltages
measured with a VOM. Rig is in receive mode.
This board may have been from an argonaut 509 (early version) before Ten Tec changed the
design and no longer used the reed relay. When trouble shooting these older radios you
sometimes have to do detective work to see what the previous owner did to the radio. I took a
look in the manual (I took one off the internet and have it in pdf format); and the green epoxy
or fiberglass board looks like the picture in the manual. The picture in the manual is not all
that clear but certainly the transistors on the brown board seem to be modern plastic
transistors more commonly seen than the more rounded ones on the fiberglass boatd above.
I am going to venture a guess..at this point..that the previous owner perhaps rebuilt the brown
circuit board or maybe all the boards. I will have to some more detective work.
I will be putting the transistor part numbers on the sketch I drew to the left. It will be published
here in a few days. I want to figure out what the previous owner did (or) maybe it was a
different board that Ten Tec made during some of their production runs. I dont mind whatever
it is ..because it seems to be working!
Another view of the brown phenolic circuit board. NOTE: Up near the two variable resistor
trimmers you see one of the rounded transistor types that appear in the photo of this board
in the manual. This gives me another clue that I think this board may have been repopulated
with different transistors.
NOTE: ABOVE voltages are for the "working control unit board" and are the voltages I measured when radio in receive mode.
The next circuit board I will be working on and checking is the SSB Generator board. This board produces a 9 MHZ output signal either SSB or CW tone. I used a Spectrum
Analyzer to check the output of this board. Another option would be to use a homemade probe using a coupling capacitor of say 1000 pf through a 5 kilohm resistor to
couple to a general coverage receiver tuned to 9 mhz. YOu could then listen to the 9 mhz ssb and cw to verify that this stage is working. An Oscilloscope or a simple rf
detection probe will also work.
This radio is almost "minimalist" in the way it works. It works well..but is fairly simple.
That is the beauty of it! A person can get in with a scope probe or simpler test
equipment and trouble shoot each stage. The crystal in the left center is the 9 mhz
oscillator. The 3 trimmers adjust the crystal oscillation frequency (slightly) for each
mode: LSB, USB and CW. The carrier balance pot is the yellow one.
I am using a spectrum analyser and a frequency counter. Here I put the probe on the
output pin of the crystal filter.
10 mhz per division and you can clearly see the output at the crystal filter. To do a
comparison of the acutal transmitter rf output I move the probe to test the transmitted output
at the dummy load resistor..see picture right.
The 14 mhz output at the dummy load which is in the antenna jack is a real small signal.
I now have formed an idea in my head that the final output stage is not working. I
suspect the finals are perhaps blown..BUT ..I will keep tracing the low level stages out
before I jump to a conclusion yet.
The 14 mhz signal on the screen above..is probably just some sort of RF being radiated
from perhaps a driver stage and being picked up by the probe which is acting like an
antenna. I listened in my radio station receiver and I could hear a 14 mhz signal but it
was not strong like it should be if the transmitter were working properly.
This is actually a 75 ohm dummy load..but it is ok for this kind of low power work. A little bit
of swr will not be of any consequence..IN FACT..the Argonuat does not have SWR
protective circuitry. It does have a built in SWR bridge. JOB #1 when using an argonaut is
to check the swr. With 5 watts power ..you wont cause too many problems if you do a test
tune on the air.
The Mic Gain control is on the right and my finger is on the cw carrier level control at
the back of the radio. Not all that convenient but I will likely just keep it as is. I may add
a small knob on the shaft to make it easier to adjust however. The 509 came out with a
front panel rf output adjustment. Im leaving the controls back here..but I am putting
small knobs on them to make them easier to adjust.
I was pretty sure I was getting 9 mhz out of the crystal filter and I made an extra
measurement to double check.
Above: I adjusted the Frequency Span to 2 mhz per cm on the screen to
stretch out the display. The large blip is the 9 mhz output the IF frequency. In
the Argonaut..the 9 mhz filter is used on both transmit and receive and is
bidirectional. So..it seems up to this point the radio is working on transmit
21 Feb 2012..I have started another page
of the 505 trouble shooting and
adjustment article. Click here for this new
page -- furthur note: 23 March 2012..I
have the 505 in operation now. I will use
it for some CW work with QRP then I am
going to put it back on the bench to do
some fine tuning and a bit more trouble
shooting some circuit boards. I will be
writing this up as I go along this year.
click here to go to the home page of
VE3AB Earl Andrews ...
(a free on line magazine for electronics
and ham radio).
This project is now operational. The 505 is now working.. March 3 rd 2012. I had to
replace the driver transistor (i used an MRF 607..( I have about 15 or so of these in stock
and I can sell the odd one here and there to hams or tinkerers like me!)..this is a 12.5db
gain transistor and I used it because I dont have many 2n4427s in stock (the original 505
driver). It works well. note: I went out and bought about 6 - 2n4427s (older parts from
1980s) from a source on ebay and I sell them to hams who are fixing or building at a
reasonable price (about $3.75 each plus postage $1.50 in Canada and $2.80 to USA).
NOTE: THERE is no real commercialism or advertisements on this "amateur" web site but
every once and a while I toot my own horn about the work I do and the parts I sell. Helps
pay for my radio/electronics hobby and this web site.
The final transistors were also in need of replacement. All three transistors I replaced
had open circuit on one of the junctions. (In other words..the transistors were "blown").
The picture below..I am trying it out on transmit with my newly acquired Ten Tec keyer.
The 505 is receiving and transmitting very well on 20 meters. I plan to test it out on the
air and make some qsos before I go back in under the hood and tidy up some loose ends
and make any minor adjustments (if and as necessary).
I bought this keyer for $40 even though it had holes drilled in the top. I will be
ordering some parts this year from Ten Tec. They still have parts for the Argonaut
509 and some for the 505 and Im hoping to buy a new top cover for the keyer when
I put my order in.
One advantage of dealing with Ten Tec is service and parts for these older
Their web site has quite a bit of information on service to these older radios.
|Want to fix your argonaut or need tips on
here is a site that Ten Tec sponsors
cut and paste into your navigation line.
|I had an email the other day from a ham in Europe who wanted to buy a
digital frequency readout display from me for his argonaut 509.
I don't sell Digital Displays or PTO rebuild kits. For digital displays for older
radios try AADE (almost all digital electronics). I bought a new digital display
for my FT301 from them and it works very well.
For PTO rebuild kits and some other mechanical and electronic parts try Ten
Tec..they still have parts for their old rigs. NOTE: I do sell some parts for
Argonauts 505,509, 515 but they are generic type devices..ie
semiconductors, diodes, ICs, and transistors (mainly). I do have "some"
very limited chasis parts but not many.
|THIS IS A multipage article--- 5 PAGES right
now...but I will be adding another page or two
down the road. (I want to do some more
trouble shooting of other 505 boards and I
want to tidy up some loose ends)
Follow the links in blue text..to continue with
this argonaut 505 article........>>>>>>>>>>