For this step, you'll need some new components. Look at the values printed on the old capacitors, then order new ones
in an equal or higher voltage. For
electrolytic capacitors, this is usually
around 450V, and for the film
capacitors 630V should cover all the
possible situations. You'll also need
some wire snips, needle-nose pliers,
solder and a soldering iron, and
optionally, a heat gun, hot glue gun,
and some bee's wax, and maybe
some brown or beige filler material
like polymer clay. Why, you ask?
More on that in a bit.
If you want to align the radio at
the end of the process — this is not
strictly necessary, but it makes the
stations come in at the correct places
on the dial — you could consider
using a signal generator with
amplitude modulation that has a
range from around 450 kHz up
through about 2 MHz, or 15 MHz if
you want to align the shortwave
bands, as well. If you don't have one,
don't worry. You can do most of the
alignment of the intermediate
frequency (IF) and radio frequency
(RF) sections with just the existing
AM stations you can pick up in your
area as test signals. It will come out
What are we
The main cause of age-related
problems in an old radio are the
capacitors. Vintage caps were made
of cardboard, foil, paper, and wax,
and just don't hold up well over time
— especially not 50+ years. After so
long, the materials have just
degraded to the point where they no
longer work as capacitors.
Dead electrolytic capacitors in
the power supply have killed many
old radios, and the coupling and
bypass capacitors can cause tubes to
fail and coils to burn out.
Last month, we got started repairing a 1937 DeWald Model 618 tube radio.
After a short history lesson, we made some basic checks on the radio's
important coils and transformers, and discovered that this radio looks like it's
in pretty good shape for being 78 years old. However, there's still work to be
done! Now, we'll go through the rest of the repair process, a first power-up,
and if all goes well we can move on to aligning the radio's tuning dial and
enjoying our resurrected antique.
By J.W. Koebel
48 June 2015
Fix Up that Old Radio!
It’s fun –
and easy –