[R-390] Recon

[Flowertime01 at wmconnect.com]

Jon W1MNK Brandon FL USA ,



You come to the right place for Help.



We do a lot more R390/A here than the R390's just because the Cargo Gods have 
given us many more R390/A than R390's.



Dave Medley now a very senior citizen did R390 support for years. He still 
has parts. you can look up his web site if you need R390 only type parts.



Hank does R390 and R390/A parts if you need things like knobs that were 
common.





do a search on R390A Y2K manual

Visit the R390/A web site for documents



Search for TM 11-5820-357-35 and down load a copy (the ARMY R390 TM of every 
day maintenance 



Army MARS "R-390 Cookbook” by A. Carmody It was written for the R390 (NON-A)



More to follow I have to go punch a time clock.



Roger L. Ruszkowski AI4NI    

This never hit the mail box for some reason (embedded hyper link now removed)

You will want a spline wrench to fit the spline bolts and RF slug rack 
adjustments.

Do you have a power cord with the connector that fits the receiver? Is it 
safe?

Place a ground strap between the receiver and ground.

The receiver since the day it was constructed would trip ground fault circuit 
breakers that were invented long after the receiver. The receiver will also 
trip the new arc fault breakers now required for bedroom circuits. If you have 
to run your receiver on a fault breaker, the input filter that allows more 
current to ground than a fault breaker tolerates, can be changed out with a more 
modern computer line filter that does not upset the fault breakers. This 
change also reduces the shock hazard of ungrounded receivers. However, NEVER 
operate the receiver with out a good ground.

The balanced antenna input is the same as the Twin coax used for early IBM 
computer networks. These connectors and that cable are available surplus. One 
pin can be grounded and the receiver feed through the other pin with a single 
wire feed. Mostly coax. 

Some times, one balanced input lead is moved over to the unbalanced input and 
the antenna is then mated to the unbalanced input connector, while the other 
unbalanced input is shorted with a wire in the twin coax input. Do a search 
and see Chuck Ripples R390 web page for antenna solutions.

Hang the front plate over the edge of the picnic table in the back yard and 
give it a bath with soap and water. Chase the water with compressed air. Rinse 
the gear train with cheap alcohol. Avoid the WD40. Blow out the gears with 
compressed air. The current preferred lube is Mobil synthetic oil. Just visit the 
station a few times and raid the empty quart cans. This will yield a life 
time supply of gear train oil. Good lightweight motor oil was used in the 50's 
and 60's. Blow the extra out with air.

Pull the IF, power transformer and audio decks. Current practice is to just 
run these through the dishwasher. Leave the RF, PTO and Crystal Osc decks in 
place for now. Once you become experienced you may want to pull these decks. 
Just to see what is under them. 

R390's had good caps in them. The R390/A's had some sorry plastic brown or 
black capacitors. Eyeball the IF deck and audio deck for any of these fat round 
plastic caps. Most were .1 or .01 by pass caps. Some 20 plus in the whole 
receiver. The audio deck has an electrolytic coupling cap. This thing liked to 
leak and the fluid eats up the printed circuit board in the audio deck. Do an eye 
ball inspection on that.

The plug in electrolytic capacitors in the audio deck for the power supply 
are near un obtain ium. Your receiver likely does not have original caps. They 
have been replaced at least once since the 1950's so they may be good for some 
more years.

Current replacement choices for the plug in electrolytic capacitors in the 
audio deck are at least the following five. You can re stuff or have the current 
cans re stuffed. You can stuff some new caps into relay cases with 8 pin 
octal sockets and plug these in to get the job done. You can build some very nice 
packaging for the new caps. You can kluge some caps into the sockets. You can 
kluge some caps under the audio deck. If you chose to kluge please do not 
commit the fact in text on the reflector here. It will cause some readers much 
angst. However some receivers have been acquired with said poor workmanship in 
place and the receivers were working. We think this is a great tribute to the 
Collins design that it will accept such abuse and still function.

Under the power supply and audio deck are sets of 47 ohm 2 watt resistors. 
Check these for value. 

Your power supply likely has the 26Z5's solid stated with a single diode. In 
this case the resistors in the power supply are no longer critical. The power 
supply mod maybe of any level workmanship. The diodes may or may not be robust 
enough. Recommendation is some modern inexpensive 1KV 1 AMP or even 2 AMP. If 
you need to do this then read the archives for some very good advice. The 
tube shield base is likely bent over to prevent a tube from being inserted into 
the tube socket.

Good modifications unwired all of the tube sockets except for the diode 
mounted on two pins of the socket. (plate and cathode pins) The tube shield was 
left neatly as unbent as reasonable. Two of the 47-Ohm resistors get left just as 
surge suppressors and to reduce the wiring changes. Most modes just added the 
diode from one plate pin to the cathode pin on each tube socket.

You will want to check the 47-ohm resistors in the Audio deck. These balance 
the load through the 6082 series regulator tube sections. If a 6082 is run 
into the ground, it burns one or more 47-ohm resistor. There is no consensus on 
how to by pass the series regulator in the R390. Most consider it worth the 
maintenance trouble. The much cleaner B+ is worth the extra heat and maintenance 
requirements.

The R390 when new had at least one alternate power supply. You changed out 
the 120/ 240-volt AC power supply deck for a 24-volt DC power supply deck. The 
DC deck had a 24-volt DC motor in and 250 volt DC generator out at about 1 amp. 
The R390 filaments are all wired in 24-volt strings. This power supply made a 
lot more noise than the 60-hertz transformer. So there is this elaborate 
voltage regulator circuit in the R390 for clean B+. Back around 2000 with the Y2K 
problem some of the Fellows were looking for some of these power supplies for 
the R390. I do not know that one was actually found. I had seen one of the 
supplies in 1968 at Fort Devens in the schoolhouse where I learned to maintain 
the R390 and R390/A receivers. In 1970 I seen a van in Korea that once had eight 
of these R390 receivers in it but the receivers were converted to 60 hertz 
and I never did locate the 24 volt power supplies stashed anywhere. The 
management back then though the 24-volt power supplies had been shipped to more needy 
people. I then asked why we were trying to keep a van and truck chassis 
running if it was missing the essential parts. The reply to that question was 
unsatisfactory.

Anyway this fine mess leaves the R390 with a serious B+ voltage regulator. It 
produces much heat. Current preference is to maintain it and use it as is. 
The R390 is considered to have better sensitive than the R390/A and the voltage 
regulator gets most of the credit for the difference in receiver performance.

Next is the ballast tube in the IF deck. If you still have one use it until 
it dies. It will die. It was and is the most failure prone item in the 
receiver. Current choice one is to rewire the tube socket for a 12BY7. This tube just 
happens to use 12 volts at the same current as the 5749 BFO and VFO tubes. But 
the filament pins are no the same as the active pins in the ballast tube. 
Another choice is a resistor plugged into the active pins of the ballast tube 
socket. You may find any of these options installed in your receiver.

The OFF / ON device under the function switch is a micro switch. When the 
receiver is left on for long periods the switch sticks and then the receiver will 
not turn off. Like wise the switch will stick open from setting around 
unused. Some disassembly and poking will return the switch to operation.

Test all the tubes in a tube tester. Make sure the correct type of tube is 
installed into each socket. Worry not about tube shields at this time. That is a 
whole weeklong topic by its self. 

Dial the receiver around to 7+000 and eyeball the mechanical alignment. The 
holes in the cams need to line up with some marks on the RF deck. The KC and MC 
change operation should be smooth. The MC detent stop is likely worn and the 
receiver will not like to stay on the MC. New detent springs are still 
available.

Check the cam racks. Your racks may or may not have little rollers on the 
bottom of the rack arms. The little rollers need to move like bearings. Flat 
spots are not good. Check the slugs. These need to move smoothly in the tubes. 
Eyeball the slugs in each rack. All the slugs in a rack should have the same 
color spot or spots. Some times a slug will break and some one may not have 
installed the correct slug into the receiver. These can all still be had.

If you find you need any part for your receiver, post some mail here with 
what you need. Some one will post back and provide the exact details of where to 
find the part. Many Fellows have a spare deck or some hand full of some part. 
Some Fellows have one or two of the tubes by the 100's. It does not pay to 
advertise. We just all read the mail and when some one ask, we post back with an 
offer. Fair Radio in Ohio has many R390/A parts and some R390 parts. If you 
need some RF deck parts, slugs, racks, gears, clamps, gear springs, these parts 
are all available. Ask here first, read your mail and see what options you 
have for any one part you need. You may want six things and find they come from 
six different sources.

Sooner or later you will want a spare set of tubes for the receiver. Not some 
thing you need to get started with.

Check the fuses. The 20 Amp DC fuse goes no where. The AC is 3 amps and the 
B+ is ¾ amps. That 20 Amp DC was for the other type power supply.

Once you do a eyeball of the RF deck mechanical, check all the tubes, check 
the knobs and switches for operation, do the IF deck, audio deck and power 
supply deck visual inspections for capacitors, burnt resistors, ballast tube and 
power supply diodes you are ready to apply power.

A couple schools of thought for power on. Some like it slow and easy. Some 
just throw the switch. Both methods work. The outcome of either process is 
repairable. One is not necessarily more destructive than the other. Your personal 
experience may vary from that of other readers.

Always read Les's mail.

Beware of Barry, Barry, Barry and Barry. I can never keep these guys 
straight. But they know a lot.

Once you have the receiver on you get into another whole field of problems.
The filaments are in strings. So do eyeball all the tubes to make sure they 
glow nicely in the dark. Weed out any with a blue glow.

Any antenna should get you some input. The receiver is double conversion over 
8MHz and triple conversion under 8MHZ. Often the receiver will not work under 
8Mhz. 

The RF deck is in octaves. .5 - .999  1 - 1.999 2 - 3.999 4 - 7,999 8 - 
15.999 16 - 31.999. So some time an octave will be bad. This tells you have a RF 
deck problem. A cam clamp, slug problem or transformer problem in one of the 
octaves.

Once you get the receiver on and operating then you can begin to do a semi 
annual maintenance procedure on the receiver. When the receivers were run 24 x 
7, after six months you have 4380 hours on the tubes. So about every 5000 
operating hours you need to do a good maintenance procedure. Back when this was a 
4-hour process. Maintenance men did two receivers a shift six days out of 8 
days. Think about 8 hours on a good weekend day.

Down load the R390/A Y2K manual. The alignment and test procedure in the 
manual will work on the R390 just fine.

If your receiver fails you in any way, post some more mail. Try to describe 
you problem as best you can. This gets you better replys.

Please tell us how your experience goes. This reflector is for the R390 owner 
operators and we owner operators read it to share and gain experience. Do not 
keep all the fun you are going to have to your self. There are many more 
readers of this reflector, than Fellows you see posting answers back to questions. 
These readers want to know what you are experiencing with your receiver. All 
the post go into an archive. Over time we see trends building in the archive. 
Pearls of Wisdom grow out of these repeated problems.

R390's are in the minority. How that you have brought one to our attention 
and are about to bring it back to life, we do not want it lost again.

Happy hobby Time to you.

Roger AI4NI
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