■ THIS MONTH’S PROJECTS
Restoring the Philco PT- 44 . . . .36
An Electronic Slide Rule . . . . . . 42
Stand-Alone DDS Unit . . . . . . . 48
■ LEVEL RATING SYSTEM
To find out the level of difficulty
for each of these projects, turn
to our ratings for the answers.
●●●● . . . . Beginner Level
●●●● . . . . Intermediate Level
●●●● . . . . Advanced Level
●●●● . . . . Professional Level
The first vacuum
tube radio I repaired
was a gift from my
It was a beautiful
Sparton wooden radio
from the 1930s. It had
an organic look, feel,
and sound that cannot
be replaced by anything
available today. I still
remember his stern
warning to be careful
with that radio. “It could
kill you!” Since then, I
have collected many
radios and have learned
a great deal about their
design and restoration. I
also learned why my
was so important.
This article chronicles the restoration of a 1941 Philco model
PT- 44 vacuum tube radio shown in
Photo 1. As I worked on this radio, I
often found myself wondering who
owned it. What did they listen to?
Did this radio deliver the original
radio broadcast of President
Roosevelt’s address to Congress,
“Yesterday, 7 December 1941 — a
date which will live in infamy ...”
The featured radio was purchased in a recent eBay auction for
US$53. Overall, it was in decent
condition. The wooden cabinet was
water damaged and the laminations
were parting. The radio received local
stations but produced a constant 60
■ PHOTO 1. Restoration complete
for this 1941 Philco PT- 44 table-top
radio. It looks and plays as well as it
did 65 years ago.
Hz hum. In this article, I will tell you
how I performed the electrical and
cosmetic restoration with emphasis
placed on the electrical restoration.
For this project, I assume you
have a basic knowledge of electronics.
If you plan on working with antique
radios, you will need basic hand tools
and a good soldering iron. A bare minimum of test equipment is required.
You can do the majority of your radio
work with a cheap voltmeter.
An antique radio can be an
electrocution waiting to happen! We
are dealing with a high-voltage line
powered piece of electronic equipment. In the old days, safety
standards were not as stringent as
they are today. In fact, most radios of
the ‘40s and ‘50s left out the #1
safety device — namely, the power
(isolation) transformer. BEWARE!
Occasionally, you will find a radio
where the power cord is connected
directly to the chassis! Therefore,
treat all radios the same way you
would an exposed live power cord.
The manufacturers did take
some safety measures, however. The
chassis, including the volume and
tuning controls, were insulated. Most