March 2013: An Argonaut 509 with a
problem on transmit. Very low power
Hello Earl,
I recently purchased a 509 Argonaut, and it seems to receive ok, but the power out is low.
It will just barley  drive a 405 amp, but I want to use it as a QRP rig, at 3 to 5 watts.
Any suggestions?

** This fellow sent it to me for repairs. I do repairs at a most reasonable shop rate of $10
per hour. Ten Tec charges $60 per hour but they have a large infrastructure to support.
In this case..I did a services for another older qrp rig. These old rigs I enjoy
trouble shooting as I have all the parts here at home in my shop and they are fairly large
with no complex and high density circuitry. Also..they do not use Phase Lock Loops or
Microcircuit/Microprocessors ect.
I do not have any programming equipment for programming EPROMS or ROM ect.
First order of business is to make sure the Fuse is correct. I
pulled a 30 Amp fuse and replaced it with a 1.5 amp fast blow.

The Argonaut 509 only puts out about 3 watts and draws maybe
1.2 amps or so on peak transmit. On receive it draws maybe 400
ma. and even less if you turn off the dial lamps using the back
Its a good idea to do an overall check of the radio you start to work on. I take pictures as well. Lots of pictures. Often with these older rigs like the
Argonaut 509 (1974 to 1976 was roughly when they were manufactured); the hardware has been changed somewhat. For example: the screws have
metal washers in this radio (the ones holding the brown metal cabinet to the chassis. That was not original for the original Argonaut. In this case..I
am doing a repair to address the low power output issue (primarily) and (secondarily) I will restring the dial string because of sag at the end of its
travel. (Thirdly): (and this may tie in with the low power output): I will change out some of the capacitors (re-capping).
I was using the Oak Hills Research QRP watt meter to
check over the rig. I disconnected the small RG174U coax
cables carrying the DRIVE power TO THE final PA stage and
measured that for each band. While I was at it..I measured
the DRIVE POWER for one of my other Argonaut 509s to
use as comparison.
--->> The defective Argonaut I was working on had
consistently good DRIVE LEVELS FOR each band. As shown
on the wattmeter; the drive to the Final PA was about 200
mw except on 10 meters where it was somewhat lower.
-->> My other Argonaut 509..(the working one) did not have
as much drive power.

--->> so the problem was NOT with the low level stages of
the transmit stages.

--->> I tested the nearby low pass filter and no problems
--->> I began to suspect that ..perhaps..there was a
problem with the control board and the voltages being
supplied there ..or perhaps the T/R relay was the fault.

I temporarily swapped circuit boards between argonauts.
The CONTROL BOARD of the defective Argonaut has the
reed relay as can be clearly seen in the photos.
My working Argonaut is the fully solid state control board.
-- They are compatible 100 percent electrically.

Swapping the control boards and testing both argonauts
with swapped boards resulted in both control boards
being declared..GOOD AND WORKNG.

I took the RF FINAL PA stage from the non working 509 and
plugged it into my working 509 and found the FINAL PA
STAGE -- you can see it in the photo under the big red
aligator clip ...anyways..the PA stage was found to be good
and working.

I did a bit more measuring using a 50 ohm load connected
to the end of the various RG174 coax cables that carry the
RF (usually about 2 to 3 watts in these older argonauts).
Sometimes even the cable can be shorted out. I finally
traced the problem down to a coupling capacitor right at
the antenna.

The problem was the .01 uf capacitor right near the
antenna connector. I removed the .01 capacitor and
soldered in a temporary jumper wire in its place..and
WATTS! See the photo of the capacitor below.

NOTE: these capacitors are commonly referred to as
Tropical Fish capacitors! They are colorful and
attractive..but Im not sure about their quality! -- Later on in
the process of working on this Argonaut 509..I came
across another of these capacitors. I noticed it had a crack
in the exterior finish near one of the leads. I removed it
from the circuit board and in a similar manner to the first
defective capacitor I came across..the lead fell off when
de-soldered and removed from the circuit! - mirror sites
new article..under construction March
I was re-capping (changing out) the old electrolytic
capacitors in this Argonaut 509. When I removed
one of the electrolytics (see the 2 empty holes in
the circuit board) pictured left! I uncovered a
cracked capacitor! - If you look closely at that
cracked will see the one lead near
the crack is bent inwards to mate up with the hole in
the circuit board! I guess this put enough strain on
the lead that a crack occurred.

I am now going to visually examine all these tropical
fish capacitors (actually I think they might be called
expoxy film..NOT SURE!).

I used a rather over-rated orange drop capacitor
with a 630 volt rating to replace this one.

Actually..NOW..I am going out to purchase lots of
extra capacitors for re-capping Ten Tec Argonauts
and perhaps the Argosy and some other older
radios like these.

In the next month..(MARCH 2013)..I should have
quite a few capacitors in stock of electrolytics and
polyester film and orange drop capacitors ect.

I'm thinking of making up KITS OF CAPACITORS FOR
THE ARGONAUT..and maybe the Argosy as well.


send one off to you at a reasonable price.
my email is

I also sell many of the semiconductors for these old
radios as well. MY MAIN PAGE
..www.ham -- has links to
my PARTS PAGES (listed by part number). Here is a
link to my main page.
Pictured here are two different control boards. Electrically they are
drop in fit form and function interchangeable. The one with the red
relay (it is a reed relay) - belongs to the Argonaut 509 I am working
on currently and troubleshooting. The "solid state" control board:
pictured from one of my working Argonaut collection.

The 505 series all used reed relays. The 509s ..when they were first
produced had reed relays..then somewhere in the production
stages..they shifted to a new design control board with totally solid
state switching. -- Actually..I worked a bit of cw on the bench with
an antenna plugged in ..using the reed relay and Argonaut 509 and
it worked real well. Nice full break in cw. -- IF the reed relay konks
out for some reason-- I dont have any spare relays right now. I think
Ten Tec would either have them..or ..they could point you to a good
place to get them.

One real nice thing about Ten Tec is their customer support for
these old radios! They still have quite a few parts for the older
Argonauts. Also..when you need a part or two..if they don't have it
in stock..they can point you to an alternate source of supply. When I
needed final PA transistors for my 405 amplifier..Ten Tec had no
stock but they referred me to RF Parts in California. and they gave
me the part number of the Transistors I needed.
Pictured left hand side the two terminal ..terminal
strip which has the RG174 coax line running to it. The
coax line carries the 3 watts or so RF from the Final
PA stage and the Low Pass filter assembly. The .01 uf
capacitor couples this RF energy to the Antenna Itself.
Also barely visible in the picture an insulated wire
that goes to the antenna circuit. The insulated wire is
for the receive section.

Shown in the picture is the new coupling capacitor.
An "orange drop capacitor" 630 volt rated. Hopefully will be more rugged than the old tropical fish
Above is a table of power output measured at the antenna

It clearly shows that low frequencies were not getting
through ..however..up around 10 meters..the power
output was not all that far off what it should be. On 10
meters..the 505 and 509 put out typically about 2 watts or
so. On the other bands roughly 3 watts.
-- So..I would say..if the capacitor had not fallen apart..I
would have measured it on my capacitance meter..and
perhaps I would find the capacitance of the defective
capacitor might have been in the picofarad range..maybe
something like 20 pf or so..instead of .01 uf. ..who knows??
Now that the RF output problem is solved..the owner of
the 509 (I was fixing this radio for a ham in the USA). He
had mailed it to me to work on. -- Anyways..I asked him if
he wanted the capacitors replaced. Called re-capping.
Ham radio operators are doing this very often now to
older radios. Radios from the 1960s and 1970s are
candidates for this procedure.

If you look closely at the picture can see 2
capacitors I replaced. The larger one is a 1000uf 35v
capacitor. I measured the ESR of the old one ..a 1000 uf
16volt grey being .15 ohm. The new capacitor is
smaller in size and ESR is quite low as well. Actually..
0.15 ohm ESR is not too bad at all..but anyways I
replaced it. The other 22 uf capacitor had a higher
capacitance of .52 ohm.

These are not high values of ESR..but ..since the fellow
mailed me this radio and I have some extra hours I can
spend going over it with a fine tooth comb..I might as
well re-cap it now. rather than later.

I have been thinking of using Tantalum capacitors in
many places to replace the electrolytics ..but decided
against it. Tantalums are a bit more expensive..but that
was not the consideration in this case.
I am not sure if the Tantalums would hold up over time
as good as the electrolytics would. Dont forget..this
radio is probably about 35 years old now. I would say it
was likely manufactured in the mid 1970s.maybe 1976 or
1977 as an educated guess.

The capacitors has some ESR but it isnt  really that bad
yet. So I decided to stick with electrolytics. The
exception is some of the smaller values of 1 uf. I replaced 3 of the 1 uf electolytics
with cylindrical tantalums 1 uf 35 volts on the audio
board..seen pictured to the left.
Tantalums..(I have read) don't tolerate spikes in
voltages and this board has an 8 volt zener diode
protecting the voltage on this board.

NOTE: the .0047 uf capacitor on the foil side of the
board. I replaced it with a smaller neater .005 uf disc
ceramic. --
this recapping is modifications. Some mods are ok..but
others may not be doing any good. I left this capacitor in
the circuit. It might help with RF getting into the audio.
These are two audio boards from two different 509s.
The one on the left works fine but I am recapping the
whole radio and this board is next. The board on the
right has a motor-boating problem. It too is going to
be recapped and if the re-capping doesn't clear up
the motor boating problem..then changing the LM380
audio chip will.

NOTE: the 505 argonaut used a different audio
amplifier system. It used two Germanium PNP
transistors. Quite often I get requests for
replacement audio output transistors for the 505. I do
have some left here but I usually have to scrounge
around to find some and then I have to match them.

I want to try and get some small company to etch a
real nice copy of the 509 audio board so that I can
completely replace the old 505 af board with a more
modern and robust board which is the af board of the
509. Both are pin for pin electrically compatible.

I have tried one qrp company but he wasnt
interested. I might next try FAR Circuits or maybe
even Ten Tec them selves. Another board Id like to
copy is the FINAL OUTPUT - PA STAGE OF THE 515. It
uses MRF 476 transistors and has a bit more power
To the left.. a before and after photo. The 220 uf grey
capacitor is replaced by a 220 v 35 volt one. The new
capacitors I am using to replace the old ones ..are
generally higher voltage rating and smaller in size. Most of
the electrolytic capacitors being produced over seas are
radial leads (leads comming off the bottom) rather than
axial..leads comming out the ends in a horizontal plane.

This means..the capacitor has to be mounted a little
different on the board..but to me it looks fine and
electrically would work just as well. Hopefully these new
electrolytics will last at least as long as the old ones.
The old electrolytics from the 509 are about 35 years old
and from what I can measuring the ESR..they are
still OK and might last at least another 5 years or maybe
more. -- Just the same..I am re-capping this radio for the
fellow in the USA. We worked out a trade. My services for
another old radio and I am giving him his moneys worth.

My shop rate is $10 per hour and I work at things and enjoy
myself while I do it and write up tech articles on the work I
do as well. If someone wants to trade electronics parts or
gear for my services...that works as well. Im retired from
government job..retired early and do this mostly as a spare
time activity..especially suited for our long Northern
Ontario winters. Summers..I do more outdoorsy kind of
things ..but I still  work on electronics too.
I did pull one capacitor that measured ESR 3.5
ohms. That ESR is over 1 ohm and is of
concern.Most brand new capacitors
..(electrolytics) measure between .16 ohm to about
.4 ohm. ONE shipment of electrolytics I got from
one bargain electronics store..measured over 2
ohms esr on their new old stock capacitors. I am
not going to use those capacitors.
When re-capping ..I mark the negative lead with
a minus sign
in black (-) . That way..when I replace the
capacitor..Im sure to get it in right way. If I cant
write in a minus sign because of limited space..I
do the other end with a red plus sign..or
perhaps even red dot.
This tester I got off ebay for slightly
over $20 and it seems to work fine.
The hardest part of the job is
de-soldering the old capacitors.
The leads are bent and you have
to work at straightening them out
while heating them at the same
time and using your solder sucker.

This pointed tool can be used to
remove leads and you can scratch
in an identifying mark on a circuit
board ..such as a plus sign or
something else.

Pictured right are two of the three
1 uf cylindrical 35 v tantalum
capacitors I used on the Audio
Board. Tantalums..I read are lower
ESR and as well they can fit into
smaller spaces. The down side of
tantalums (I read) are that they
cannot tolerate spikes of
voltage..and I did not want to use
too many tantalums as a result.
There is an 8.0 volt  zener diode
protecting the circuitry.
Alot of the components..if they sit
on the shelf or parts bins..they
oxidize. I clean them scraping
them with a blade of the blade of a
screw give the solder a
good surface to stick to.

Pictured of the new
electrolytic capacitors that was
installed on the audio board near
the LM380 AF amp chip and
link to my next page concerning
this particular restoration of this

th March 2013. and is under
construction currently.
Left..another defective capacitor replaced with a new
modern (and hopefully more rugged) orange drop

The only orange drops I had were
the 630 V ones..which is over kill. I am going to be or tommorrow..some new capacitors
which are lower voltage rating orange drops (100 volts
would be adequet) and I will order quite a few extra for
my own work and for filling orders.

FOR YOUR ARGONAUT.. feel free to email me.
Link to my home page or
www.ham (mirror sites).
The photo to the left was high resolution and turned out
very nice.
I just noticed now..IF YOU LOOK CLOSELY AT THE
"TROPICAL FISH" style capacitor next to the metal IF can..

you will notice a slight crack in the epoxy coating of the
.0022 uf capacitor. Could indictate a problem that could
occur. I wonder if these capacitors came from a bad
production batch?? Anyways..I will be replaceing this
capacitor as well..since I am recapping the boards.
The problem with low power output of this Argonaut was traced to one single
component..the defective coupling capacitor that couples power from the terminal
strip connection the RCA jack on the back of the Argonaut. I replaced it now
with one of the popular orange drop capacitors at 630v rating. Over-rated to be
sure but I had no lower voltage orange drops on hand. I am ordering some for
future work and will have some available in small quantities to other electronic
hobbyists. (I sell parts like these from time to time).
I have actually found more
cracked epoxy capacitors like
this I have been taking
a closer look under
magnification. I will be
replacing some of these
Tropical Fish capacitors in this
509..The ones that look FISHY!