CLEANING AND RESTORATION OF AN R-390 RADIO
This is just a start. I intend to expand this from time to time.
Most of the R-390 (non "A") radios I have seen are dirty
and generally pretty disgusting. This is due to a number of
of factors such as old age (these radios were all built in the mid
surfeit of cigar smoke and general neglect. However this is such a
piece of equipment that it will withstand some pretty rigorous treatment
come out smelling (and looking) like a rose. I was first
shown the cleaning technique by a Tektronix Tech in Dallas many years
1. First strip the radio down to its component parts which are:
RF sub assembly See
VERY IMPORTANT NOTE BELOW.
IF sub assembly.
Audio sub assembly.
Calibrator sub assembly
Web containing the
two 10 turn stops.
Back panel and wiring
2. When you have done all this you will have the bare chassis
which will be covered in grease, dirt, burn marks, mouse
droppings and other gunk. You will note that this is a welded unit.
The side and internal panels are permanently attached to the
baseplate and in some places painted. After you have
scraped all the gunk off you will find the baseplate is zinc coated
and comes up nice and shiny. You will also have several
boxes of hardware such as knobs, screws, meters, springs and stuff.
I try to keep them separated into various piles so I
remember where they came from. An empty egg carton is
useful for this.
VERY IMPORTANT NOTE:
You will notice screwed on to the front of the gearbox a mysterious
do nothing Green gearwheel. If it is not there you are in deep trouble.
After you remove the front panel and before you do anything else remove
this green wheel and install it to the right of the large brass gear
the center. It will engage in a gear behind this. Be sure it is firmly
to the shaft. There is an oblong slot in the wheel which
must be aligned with the slot on the shaft. Failure to do all this
result in loss of mechanical synchronization as soon as the RF deck
removed. This will cause you much wailing and gnashing of teeth later.
3. Here is the basis of the cleaning process. The ingredients you need
A 409 sprayer.
A wad of fine steel wool
A can of WD-40
A can of deoxit
A garden hose
Several gallons of distilled water.
An oven. Hot Arizona sunshine is a good
substitute for this and makes the XYL happier.
Not all this stuff is used on all units as I will describe.
4. For the main chassis spray it well with 409 and rub with
0000 steel wool until it is clean and shiny. Now hose it off
with the garden hose. If you live in the Desert the water will
come out near boiling point for a while so be careful.
After the chassis is clean dry it by your preferred method.
When perfectly dry repaint the painted areas. I just rough
it up a bit with steel wool and paint over. I use
Rustoleum Dark Machine Gray which is close to the original.
Your chassis will now look like new.
5. Remove all the tubes and tube shields and then do the same for
each of the sub assemblies EXCEPT the RF deck which needs more attention.
Don't be frightened to really saturate with the 409 both inside and
Let soak for 5-10 minutes then hose out until all trace of soapiness
is gone. NOW sluice well with distilled water to remove the residue
residue from your local water which is not real pure right!!
Dry thoroughly. These units will all now look new (almost!)
6. For the RF deck start by removing the slug racks and the RF coils.
and discard all the springs which will be rusty. The coils are held
in by two
captive screws accessible through holes in the top of the cans.
Now start the cleaning process with the gearbox. Sluice it well
with WD-40. I mean well. Wash out all the accumulated gunk and
dirt. WD-40 is cheap so don't be afraid to use it. It is a good
idea to remove the counter before you do this. Now follow this with
the 409 garden hose and distilled water treatment. Make
sure it is thoroughly dry. I use a hair dryer to be sure
all moisture is gone. When all this is done lubricate the gears
sparingly. I use Mobil 1 synthetic gear grease.
7. Use deoxit on all the switch contacts. Don't forget the
switches on the front panel. Clean the wiring harness also
with the 409 treatment.
8. Repaint the front panel. The baked on enamel is extremely
difficult to remove so I just rough it up with steel wool
and paint over it. Be careful not to paint too thickly
or you will have trouble filling in the lettering. This I do with
a lacquer stick. Takes a little practice but looks fine.
MUCH MUCH more to come.