71 Clean without damaging
Description
This article is from the Antique Radios And Phonographs FAQ, by Hank van Cleef vancleef@netcom with numerous contributions by others.
71 Clean without damaging
The chassis of my radio is covered with a thick layer of dust, fine
dirt, and underneath is a film of brown crud. How can I clean this
thing up without damaging it?
This particular topic gets a lot of discussion and advice, some of
it very bad. Your radio has some irreplaceable components, and if you
use the wrong methods, you can make a junker out of a restorable set in
a hurry. There are some things to keep in mind:
a. The chassis is probably cadmium-plated steel. Some radios
were made with nickel-plated steel (looks green when corroded),
copper-plated steel, or chromium-plated steel. A few chassis were made
of aluminum. If it is a dull silver color, check with a magnet. An
aluminum chassis is non-magnetic, all of the steel chassis are magnetic.
b. The dial face may be a water-soluble paint or a decal.
c. Colored knob markings (lines and dots, as well as letters
filled with color) may be water-soluble.
d. Any silk-screened surface markings may come right off.
These include tube layout information on the chassis, inspector's marks,
and other printing.
e. The tuning mechanism may be stiff because of petrified
lubricant in various shafts and rotating elements.
f. Coils, IF transformers, and tuning condensers may be
difficult or impossible to replace if you damage one.
g. If the radio is complete, tubes in place, the crud and dirt
is on top of everything, not in the electronics. You want to get it off
the radio, not melt it down so that it flows into the working parts.
You can remove the tubes. Make sure that the tubes are clearly marked
as to tube type, and make sure you have an accurate diagram so that you
can replace the tubes in the same sockets you removed them from. Get a
pencil and piece of paper and make notes about things you move,
disconnect, or take apart, so that you can get everything back together
the way it was originally. Begin by vacuum cleaning the set, and use a
soft brush to loosen dirt while keeping the vacuum nozzle near the brush
so that it will pick up loosened dirt. If you find mouse droppings, be
prepared to examine the set closely for damage from mouse pee. Gently
brush off the tuning condenser, being careful not to bend the plates.
Once the surface dirt is off, you can begin to consider how best to
remove the crud, and how far to go with the cleanup.
There are two things that are very poor to use around electronics: steel
wool and soap-type detergents. Steel wool will shed little particles
and raise havoc. Soaps and liquid detergents leave residues that can be
hard to remove. Liquid detergents also do a fabulous job of softening
and removing silk screen inks, water soluble dial markings, and tube
markings, even those that may be safely soaked in water for a few
minutes.
Start on the chassis crud by using a damp rag moistened with plain
water. Don't slosh water onto things. Most tap water is safe to use
around electronics, and is an excellent solvent. I note that I have
refurbished electronics that have been immersed for days in fresh water
after they have been allowed to dry out, and found very little damage,
mostly to capacitors. If the crud comes off with water alone, continue
with the damp cloth treatment. It may be slow, but it will leave a
clean surface with little residue. Finish the job with moistened Q-tips
to get into various nooks and crannies. Be careful that you don't
remove marking inks and paints.
A stronger alkiline solvent is clear household ammonia. This also
evaporates without leaving a residue. If water is not melting the crud,
try a little ammonia on a Q-tip. Use the ammonia straight, and if it
gets results, use it on a damp rag to moisten the chassis. Generally,
once ammonia-sensitive crud has been melted, it will come right off
using a rag dampened with water. Be careful not to get ammonia on a
shellac wood finish---it will cut the shellac and leave marks.
If this doesn't get results, try a mild acid---clear cider vinegar. Use
the same methods as with ammonia, finishing with a rag dampened with
water.
By this time, you should have most of the removable crud off the
chassis. Some other solvents to try---only in small areas with Q-tips:
Isopropyl alcohol. This dissolves a great many things, including flux
rosin, some marking inks, etc.
Trichloroethane (GC Electronics "Chloro-Kleen"). Also dissolves many
things. Don't use on plastics until you have checked to make sure it is
safe. Chloro-Kleen works very well on phenolic and ceramic-mounted
switches such as bandswitches and pushbutton switches.
Lacquer thinner. This is a "court of the last resort." It is a
powerful solvent that will damage many plastics, remove a lot of marking
inks in a jiffy, and generally raise merry hell if you get it in the
wrong place. Use on metal parts only.
Also pay attention to the various warnings about flammability and use
only in well-ventilated areas.
Corrosion on cadmium-plated chassis generally does not respond very well
to anything. You can use Naval Jelly to improve the situation,
particularly if there is visible rust. Light fingerprints often will
respond to automobile polish (Dupont No. 7 is good). This treatment
(followed by an application of Simoniz paste wax) will make many
lightly-scratched plastics look like new.
The best solvent for use with petrified lubricants in tuning mechanisms
is diesel fuel. If there are separately-mounted shafts or gear
mechanisms, you can often take them off----just make sure you can get
them back on again, and positioned properly. Watch for spring-loaded
double gears in gear mechanisms that need to be preloaded when you
assemble them. Shafts should be relubricated with a light grease like
white Lubriplate---use only enough to leave a film on the parts needing
lubrication, and wipe off the rest. Gear trains generally work well
with a little 3-in-1 oil on axle pivots and a film of lubriplate on the
gear teeth. A stiff volume or tone control will generally respond to a
drop of 3-in-1 at the end of the bushing---use only a drop, and wipe it
off after about 5 minutes.
Tube washing gets a lot of attention. Keep in mind that washing most
tubes won't make them work any better. Before you start, make sure that
the tubes are clearly marked as to what they are. While there is no
mistaking a 6A7, a T-9 beam power pentode with no markings may be a
a 6W6, a 25L6, a 35L6, a 60L6, or a 6V6. A 50L6 plugged into a 25L6 or
35L6 socket can produce interesting symptoms that can be very hard to
diagnose. Contrary to popular opinion, tube markings on glass will come
off, some more easily than others. During the 1950's and 60's, tubes
were specifically marked with easily removable markings in an attempt to
thwart a grey market in used tubes being washed, reboxed, and sold as
new. Generally, just holding the tube under flowing water will rinse
off most of the dirt--- a little help from rubbing the surface with a
thumb where it is not marked generally gets fine results. Use a china
marker to marked the type on any tube that isn't clearly identified, and
let them dry thoroughly before reinstalling. Tubes that are loose in
their base, or have a loose top cap, respond to squirting a little
superglue into the gap. Make sure, in the case of a loose base, that
the leads aren't twisted (and shorted).
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