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1951 Admiral
model 5E22 |
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1951 Admiral 5E22, purchased at a hamfest in 2013
for 10 dollars.
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This came from a Hamfest in Sellersville, PA. It
was basically the only thing I bought that day. I didn't notice it
at the time, but there were some nasty scratches right over the word "Admiral"
at the bottom of the gold dial. The
cabinet also had scratches. Someone had waxed the cabinet and didn't
get all the wax out. This made the scratches look
worse. There was also some white paint on the right side. It looked
like it was from an impact. The knobs were pretty bad.
Hey, it is 62 years old. I have more
scratches than that, and the radio is older than me! (barely) |
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Before and after. Eight capacitors, two resistors
and a vacuum tube were replaced. When I was done... it
didn't work! |
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Initially, the only sound the radio made
was a very loud hum, caused by bad filter capacitors. After replacing the capacitors
the humming stopped but
another problem arose.
While the set was warming up you could hear a radio station
for about two seconds, then it would be drowned out with
static. The static wasn't
coming from anything in the room, it seemed to be coming
from inside the radio!
This really had me
scratching my head as I checked almost everything, so I turned to those helpful guys on the
Radio Board.
Among other advice, they told me the set might have
Silver Mica Disease.
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"Silver Mica
Disease"
or
"Electrolytic Electromigration" |
In the 1940s, '50s and '60s silver
mica capacitors were made by
depositing a layer of silver onto a sheet of mica. This is an excellent way to
make a high
quality capacitor if the silver and mica are sealed in
plastic.
However, if the silver is exposed to air it will oxidize.
To make matters worse, in an electric current the silver will
migrate, atom by atom across the mica, trying to reach the silver on
the other side. When it does it will vaporize in a tiny electric
arc. The process repeats over and over causing a steady static. |
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The capacitors in question are inside
the IF transformers!
Are you kidding me??! |
An IF "can" from a deceased radio was
substituted. The radio
came back to life. Dang, now I have
to operate on the IF cans. |
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One of the IF (Intermediate Frequency) transformers. |
Two capacitors, one for each coil, are contained
on a single mica disk.
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| Notice the number 75 printed on the
mica disk. Each capacitor was rated at 75 Picofarad.
Obviously the value has changed, now that some of the sliver
is missing. Now is a good time to cut the mica wafer off and
replace it with two new capacitors, but I wanted to see if
the radio would work the way it was. |
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What is this stuff between the two
capacitors?
It's Silver Mica Disease! |
Each silver bridge was removed by
scraping it off
with a small
utility knife. |
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The case was polished for two hours with a polishing wheel in an
electric drill, mounted in a vise. Almost every scratch was polished
out. |
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The radio now works very well. When it was
first turned on only a small amount of adjustment was needed.
There is enough silver left on the capacitors in the IF cans that
adding new mica capacitors isn't necessary. |
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The knobs. |
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The gold colored
steel inserts have rusted. |
After cleaning and painting. |
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| I didn't know how I'd get the metal
inserts out without damaging them. The knobs looked pretty
cruddy, so I dropped them into a cup of hot water to soak
before I took a toothbrush to them. I noticed a bubble of
air came out. There was air behind the disks! I boiled a cup of water in the microwave and dumped it onto the
knobs. The expanding air pressure popped both metal inserts out!
A day later it was off to an automotive store
with Andrea to find a matching gold color. She spotted it
right away. The metal disks were sanded and painted. AFTER I
painted them I noticed we had purchased a high temp engine
paint. The disks would have to "cure" at 200°F for 7 hours.
No problem, I put them on the radiator.
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The next day we raked leaves. Andrea
stopped me in the middle of raking and told me she had taken
the disks off the radiator and attached them to her boot.
Then she lifted her pants leg to show me.
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Why did she put
them on her boot? Did she lose her mind?
Then I saw the raised
rims on the disks. Those disks came with the boots! She does this crap to me all the time. |
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