VINTAGE RADIO
By JOHN HILL
Restoring an AWA Radiolette receiver
In the mid 1930s, AWA produced a popular
series of mantle radios under the tradename
"Radiolette". The Radiolette appeared in various
shapes and sizes and was still a popular receiver
during the immediate post-war era.
The early versions were mainly in
black or brown bakelite but some coloured cabinets were also made. These
were mostly in "ivory" or "jade". The
coloured models have not survived in
the same numbers as the bakelite models - perhaps there were not as many
made?
These early Radiolettes were nicknamed "Skyscraper" models because
their shape was vaguely similar to
that of the Empire State building in
New York.
There was also another version of
this little mid-1930s receiver. Although the chassis was virtually the
same, it was housed in a timber cabinet (still with skyscraper lines) but
with a small round dial instead of the
square dial that characterised later
models.
All of these mid-1930s Radiolettes
are very collectable items and are
much sought after by vintage radio
collectors. For this reason, I was quite
pleased when I recently obtained a
1934 timber cabinet version for a very
reasonable price. Although the set was
Radiolettes were still being produced in the early post-war years. This 4-valve
model has octal valves and is oflate 1940s vintage.
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SILICON CHIP
not working, it was all there, in excellent condition and completely original throughout.
This month's Vintage Radio story is
about restoring the old Radiolette to
working order. As with most early
superhet receivers, there were plenty
of things to check and replace, but
that is fairly normal when working on
a radio receiver that is nearly 60 years
old.
Routine checks
In keeping with my usual routine
procedure, I started the job by checking out a number of vital components
- the ones that often break down in a
receiver of this age.
Continuity tests on the power transformer primary and high tension secondary windings showed that they
were OK, as were the radio frequency
(RF), oscillator and aerial coils. The
intermediate frequency (IF) transformers also tested OK. Preliminary checks
of this nature are very worthwhile, as
they will quickly locate any trouble
spots.
The loudspeaker was the first major component to fail the test. While
the field coil checked out OK, the
output transformer primary winding
was open circuit. This is not an uncommon fault with valve radios and
the output transformer should always
be a suspect component until proven
otherwise.
Fortunately, luck was on my side
for a change as a search through my
spare output transformers revealed a
similar unit in working order. It was
quickly fitted to the loudspeaker
mounting and wired up accordingly.
That was one problem taken care of.
The valves were next and they were
cleaned and tested. All were in excellent condition with the exception of
the 80 rectifier which was very sick
The 1934 Radiolette in unrestored condition. The set had
been well cared for in its 57 years and was completely
original throughout.
indeed. This suggested that there
could be a problem somewhere in the
high tension circuit, a suspicion that
proved correct later on.
These early Radiolettes vary considerably in their under chassis construction. Some have little component boards with numerous capacitors and resistors attached, while others have a big bundle of parts which
are taped together and attached to one
endplate of the chassis. Neither arrangement is particularly easy to work
on.
My little Radiolette was of the bundle type and if readers care to check
with the appropriate photograph, the
word "bundle" is about the only word
one can use to describe this type of
construction technique. Obviously,
the printed circuit board hadn't been
invented in the 1930s.
Replacing components in the bundle must be done carefully in order to
maintain the existing circuit. Capacitors should be removed one at a time
and appropriate replacements fitted
in their place. With a receiver of this
age it is advisable to replace all of the
paper capacitors, whether they be in
the bundle or elsewhere.
Now most old capacitors are well
marked. If a capacitor has a value of
O. lµF, then it usually says so somewhere on the casing. Not so with the
Radiolette's capacitors.
These particular paper capacitors
are colour coded with three colours,
This 1936 bakelite Radiolette is a more common version
of this popular range ofmid-1930s receivers. Unlike the
timber version, it carried a square dial.
The high voltage electrolytics are installed in a square metal can on top of the
chassis where the thin asbestos heatshield does little to protect them from the
hot rectifier valve. The asbestos was made safe by sealing it with clear Estapol®.
similar to the way a resistor is marked.
In this case the colours have the values of the standard colour code and
the capacitance is in picofarads .
For example, consider a capacitor
that is marked red, green and yellow.
The capacitance is worked out as if it
were a resistor; ie, the first colour
represents the first digit, the second
colour the second digit and the third
colour the multiplier in tens. Thus,
red is 2, green is 5, yellow is 4 =
250,000pF or 0.25µF.
I hadn't come across this system
before and, initially, I could only assume it was similar to that used for
resistors. After checking some of the
capacitors with a capacitance meter,
my assumption was confirmed.
Electrolytic capacitors
The paper capacitors weren't the
only capacitors in need of replacement - the electrolytics were also on
the sick list. Time treats old electrolytics most unkindly and as these particular capacitors were approximately
5 7 years old, it seemed logical to reJANUARY 1992
59
There's not much room underneath the chassis of a mid-1930s Radiolette.
Taking up most of the available space are the IF coils and the 3-gang tuning
capacitor. The inaccessible volume control potentiometer is to the left of the IF
cans. It has a somewhat unnecessary friction drive reduction connecting it to
the control knob shaft.
place them all without question.
There were two 25V cathode bypass electrolytics in the bundle which
needed to be replaced. One carried a
value of 25µF, the other 5µF. Both
were totally inoperative and judging
by the cracks in the ends of them,
they had dried out many years ago.
The replacement electrolytics were
modern types rated at 22µF 63VW
and 4. 7µF 63VW.
As ail the replacement capacitors
were small modern types, the bundle
looked a bit gutless when the change
over was completed. That's one good
point about replacing old capacitors
with new units - the modern varieties
take up much less room.
The two 8µF high tension electros
were next on the list. These are housed
in a steel can which is bolted to the
chassis next to the rectifier valve. This
w~uld be about the worst possible
place to mount the electrolytics, since
A front view of chassis. The large metal container at the
near end houses three of the five valves. The loudspeaker
is an electrodynamic type and was still in working order.
60
SILICON CHIP
it subjects them to a considerable
amount of heat. The thin asbestos
heatshield becomes quite ineffective
after the set has been operating for
several hours.
Removing the top of the can revealed that the original capacitors
were sealed in a mass of black wax.
They were quickly released by gently
heating the can, so they were not as
difficult to remove as first thought.
One of the electrolytics was completely short circuit, which could have
been the reason for the almost defunct rectifier valve. Any short circuit
or high leakage situation in the high
tension line will over-work the rectifier.
The high tension electrolytics were
replaced with modern 450VW units.
They were reluctantly installed inside the chassis mounted can and the
hot working conditions ignored. There
is little room under the chassis for
additional parts.
Getting it going
A quick check of the resistors with
an ohmmeter showed that they were
all OK and within tolerance. The end
was near; all that remained was to
clean and lubricate the dial mechanism, and fit a new power cord. The
set was now ready for a trial run.
The little receiver worked surprisingly well and required very little in
the way of re-alignment to bring it to
peak performance. Even the loudspeaker sounded OK which isn't always the case with an old Radiolette.
The little AWA's output transformer was in need of
replacement (primary open circuit). Fortunately a spare
transformer was discovered lying in my junkbox.
RESURRECTION
RADIO
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All of the original paper and electrolytic capacitors were replaced. This
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The infamous bundle: this mass (mess) of components consists of paper and
electrolytic capacitors, carbon and wirewound resistors, and insulating pieces
of cardboard. The bundle need not be removed from the receiver and is best left
hanging on its many connecting wires while individual components are
replaced.
These small electrodynamic speakers
frequently have a buzz or rattle in
them and often sound every bit their
age.
I was very pleased to note that the
volume control was smooth and quiet
in its operation. Replacing a volume
control in one of these radios is one
"helluva" job. In fact, when it comes
to servicing, there are few sets worse
to work on than a mid-1930s Radiolette.
Running the set continually for a
number of hours proved that everything was working well. No overheating of the power transformer or the
loudspeaker field coil was evident,
which is a good indication that nothing is being overloaded or working
abnormally.
The mid-1930s Radiolettes are very
collectable radios and have an appeal
that many other receivers of that era
lacked. I'm quite sure that most collectors would consider them, as I do,
to be "classic radios" of their era. SC
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JANUARY 1992
61
