Argonaut 505 repair June 2012 by Earl VE3AB - an interesting repair story.
I received this Argonaut 505 in mid June this year by mail from USA. This
is a little story of how the repairs went with photos and movie clips too!
This early production 505 has a dial skirt with 5 khz markings on it. As
evident from the picture; the dial cord needs to be tightened up with a new
elastic tension cord at one end and likely a new dial cord.
Ten Tec still sells spares for the 505 and I have these items in stock in my
basement shop.
505 unpacked and ready to check out.

Quite a few times..people have wanted to send me their entire radio..ie the FT301 for
repairs. I remind them of the costs for postage.  This cost the fellow about $40 to send
here with signature confirmation ect. My rather low shop rate of $10 per hour somewhat
offsets the high cost of postage.
I am making up some voltage charts for troubleshooting. Previously in February of 2012; I had worked on my own Argonaut 505 and I made measurements and
charts. A person can use the charts in the 505 manual but it takes time to figure out the pin outs and I want a very visual set of charts so I can make
measurements and do tests in a hurry.
The above pictured was in receive mode. Now..I am making a chart for transmit condition. This being June13th 2012 and I am going to have both my 505 on the
bench and the 505 Im working on. I will be using my working 505 as a benchmark for voltage measurements and I will be making some more charts as I go
through the circuit.

The Argonaut 505 that I am trying to troubleshoot now..from a fellow in the USA..has issues on receive that I have to iron out first. It is..or at least..was..dead on
receive. I traced the voltages at the function switch (OFF SB-R, CW, SB-N and LOCK).  I cleaned the function switch with some tuner spray and the near by AF
gain Control and RF gain control. -- I now have receive but it is unstable and with oscillations. The oscillations are loud and something I have not encountered
before..but at least the resonate control works and the AF board is working and the control board seems to be ok. I did a bit of board swapping with my good 505
to confirm these 2 suspected problem areas.

I actually made a separate page with a few movie clips of where the repair stands now. The oscillations are loud. There is an instability as well. Im thinking..that
maybe the transmitter may be running at the same time as the receive or perhaps some circuit is self oscillating or something. Maybe it is an audio oscillation
problem or RF or a bit of both.
CLICK HERE FOR THE PAGE WITH THE MOVIE CLIPS...CAUTION..THEY TAKE A GOOD LONG WHILE TO LOAD ONTO THE COMPUTER
SO PATIENCE AND A HIGH SPEED CONNECTION ARE NECESSARY. Some people tell me the clips dont load for them..but others tell me they do..but it does take a
good bit of time depending on your connection speed and the age of your computer.

At this point..I have sunk about 2 solid hours (I figure) into the rig troubleshooting so far..and at my (very reasonable) ($10 per hour rate)..it is about $20 of labour
so far. I have an idea that maybe 4 to 5 more hours or so will be necessary to repair this radio.
Argonaut troubleshooting starts with the control board.
In this particular case..the control board checked out fine.

The control board has the TR switch and provides the T voltage (to actuate
circuitry in transmit mode), the R voltage (to actuate voltage during receive and
it provides one or two other voltages. It is a primitive brain of sorts for the rig.
This page (and the Argonaut 505 itself) ..was being worked on .20
june 2012. It was a hot day and I stayed in the air conditioning
today!

As I write this on a "hot summer day" I am sitting comfortably in
my air conditioned home up here in Elliot Lake Ontario CANADA.
YES..we need air conditioning even up here in the north!!

Anyways..This radio is just being put back together for the fellow
in USA. All my work is almost now done on it.

The audio board and the TX RX mixer (transmit problem) now
solved. I had to order in a CA3053 IC for the TX mixer. While I
was at it ..I ordered 5 more spares of this communications IC
from the 70s/80s. I am going to sell them for $8.50 each and I can
send in a padded envelope ($1.51 Canada and $2.80 USA) for
hams who want/need one or two.

I have capped the repair time at 9 hours and so at my rather low
labour rates that is $90 labour. I will be operating the rig and
checking it out..right after I restring the dial.

The parts charge for this job was $30. To get it across the USA
border here into Canada it cost about $40 one way. I suspect to
send it back to usa about $45.

I also do mail order repairs of smaller rigs and accessories and
circuit cards. IF you send a number of the plug in circuit boards
to me..for rigs such as Atlas 210x, FT221, FT301 Argonaut 515,
509 and 509 I can plug the boards into my good working rig and
narrow down the problem card quickly and do the repairs here.
Beside the control board is the SSB filter board and the heterodyne oscillator.
The trimmer capacitors are selected one for USB or LSB or CW and the crystal is
tweaked somewhat by the capacitors to put out the right frequency for mixing and
cleaning up with the filter. Filter is towards the top of the page. This ssb filter
board checked out OK in the argonaut I was troubleshooting for the fellow in USA
THE pa FINAL AMPLIFIER board checked out OK. The low (very low) transmit level signal
output turned out to be a problem with the TX mixer (CA3053 IC). I have corrected that
problem.
The AF board (pictured left hand side of page) has a problem. I removed the two
germanium transistors (top of circuit board) and tested the junctions with a VOM
and they (seem to be OK)..so I think it might be one of the capacitors..perhaps an
electrolytic. I tested the electrolytics with a VOM to get an idea of their merit. I also
tested the other transistors on the board.

Since this is an OLD BOARD from the early 70s..Id say it is time for recapping the
board. Cant hurt..it is not working. Maybe that will cure the problem..we will see.
Pictured right ..low level signals on the TX out pin (center over the trimmer capacitor) a
wire leading down/over to the driver transistors on transmit. On receive..pictured left
on spectrum analyser. On receive...not much on the spectrum analyser at the TRANSMIT
MIXER OUTPUT PIN ON THE CIRCUIT BOARD.
See the captions below for details on
TRANSMIT MODE.
This is what the output from the CA3053 transmit mixer should look like on transmit.
Band is 14 mhz. I beleive the spectrum analyser was set for 2 MHZ per division.

Not all that important the exact frequencies..but relatively strong signals and the
spurs will be cleaned up by filtering stages in the argonaut 505.
This is the same test point on transmit with the ailing argonaut 505.

I changed in a good RX TX mixer board and the display was like the one on the left.

Problem solved.
Below the cheapie radio shack desoldering iron. It does a pretty good job. There is a squeeze
bulb on this rig to suck up the molten solder off the joint.
JUNE 20 2012..I will be restringing the dial today. I have printed out some detailed
instructions. I made a text file and it can be found on this page for
MANUALS on my web
site here
BELOW: PICTURED LEFT ON THE SPECTRUM ANALYSER:

a healthy transmit mixer output signal vs on the right
pictured..the defective TX-RX mixer board signal on transmit.
Step nr. one...remove the old dial string assembly and turn the PTO/VFO knob so
that the curser would be at ZERO to the far left of the panel plate. I turned the knob
fully counterclockwise as per the instuctions. ( I have published these instructions
in a text file on my "MANUALS PAGE"-- By the way..MY "MANUALS PAGE" has all
three older Argonaut manuals on it in PDF form. Also some other older solid state
rigs (the kinds I work on) are on this page as well.
I have extra string and the stretchy black cord. Comes in handy when people send
you stuff to work on.
Here I am installing a new plastic cursor. Note that I used a patch of packing tape to
keep the mini black bungee cord in place with its proper tension for a zero dial
setting while I measured the spot to make a loop on the cursor
This picture turned out a bit blurry..but I tied a knot on the little peg from the
tuning dial. I used the dial cord I had purchased from TEN TEC. I wrapped a couple
of turns on the PTO shaft and it all seemed to work fine.
I used a dab of Q DOPE on the knot on the PTO shaft and as well the dial
cursor knots just to keep the knots from working their way loose over time.
The knot or loop on the left side of the cursor was secured with a piece of bare
hookup wire to form a little clamp.
Thats it for now..22 June 2012. I will be writing more in the next day or two as I package up this
argonaut 505 and give it a test run..then send it back over the border to USA.

73 Earl VE3AB (PS my qth is Elliot Lake, Ontario..which is across the lake from Upper Michigan.