The Wartime Civilian Receiver
The Wartime Civilian Receiver, popularly known as the ``utility'' set
(in keeping with the name other wartime lines of utility goods such
as furniture and clothes), was intended to be produced as a functional
item, with few frills. As a result it was hoped to maximise production
efficiency and avoid detracting from the war effort. Radio equipment for
military use had already played a prominent role in the armed forces and
manufacturers of domestic radios had in the main turned their production
focus to equipment for these armed forces users (such as aircraft radios).
The combination of an understanding of the importance of keeping the
public informed of the latest news (in contrast with cinema newsreels)
and a shortage of domestic receivers persuaded the Radio Manufacturers'
Association (RMA) to come up with a standardised Government Approved
design. The design was the work of Dr. R. G. Reynolds of Murphy Radio.
All manufacturers were to produce a set which was functionally the same
(to avoid competition on account of features, and to allow for economy
through parts reuse).
The set was produced in two versions, for Mains or Battery power.
Fortunately the example at the Museum is a mains version. The Battery
version would have used a large glass LT accumulator and HT batteries,
with limited life, and which became unavailable after about 1950.
It does the designer tribute that such sets are still around and working
today fifty years later. The solid utilitarian design certainly helped,
many of them moving out of the house to barns and childrens' bedrooms
in the post-war years. An example recently turned up, thickly coated
in white paint! Plant pot rings on the top of the case are apparently
the most common damage.
Looking at the set it is easy to imagine the primitiveness of pre-war
radio sets, that is in fact not the case as some of the early Pye examples
at the museum show. Features which the buyer had come to expect in
receivers from the pre-war era had to be left out to conserve materials.
One such feature was the band change switch; early band change switches
made up of multiple paxolin wafers with silver plated contacts, and were
both expensive and unavailable since they were required for other war
effort applications, so the decision was taken to make the set cover a
single band, the Medium Wave Band (MW) where the BBC's programmes could
be received at that time. An interesting fact which also may have
affected this decision is that at the time, the BBC were doubling up
its transmissions onto the same frequencies in geographically separated
areas to try and make Direction Finding (and hence bombing) based on
using the BBC's transmitters as beacons difficult). As a result some
services which were served by a single transmitter, such as the precursor
to the Long Wave Radio 4 service on from Droitwich were closed down for
the duration, and thus so this single band restriction was not as severe
as it may seem now.
Although these sets were produced by over forty manufacturers, the
particular manufacturer of a given set was not revealed to the purchaser,
who might presumably have had a preference for a certain manufacturer.
It was in fact encoded in the serial number plate to help repairmen (who
needed to know from whom to claim warranty replacements), but the table
which related these codes to manufacturer was considered "confidential
to the trade". Similarly Valves in these sets were given special BVA
(British Valve Association) codes which hid the manufacturer, a typical
line up would be BVA273, BVA243, BVA 264, BVA211. These might
more conventionally be called ECH35 (changer), EF39 (IF amplifier),
EL33 (output) and DW4/350 (rectifier). The valves in the
Museum's set are all original BVA numbered types and still work!
The loudspeaker, unusually the for the time is a permanent magnet design
to save wire. It was usual in sets of this era to have an electromagnet
field coil which doubled up
up as a power supply smoothing choke removing hum from the output sound. The
tone control was dispensed with as an unnecessary luxury! The tuning dial
dispenses with the complex glass and string reduction gearing commonly
used and replaces this with an austere metal plate with an index painted
on a disc behind attached to the tuning capacitor.
Manufacturers were allowed to adapt the design specifically with the aim
of using up old stock of components which they had on hand which were
not required for the war effort as a result numerous small variations
appeared, especially as regards the coils.
The detector was a rather unusual
and unreliable device called a Wesector, a metal rectifier, which was an
early form of solid state diode. In fact they were so unreliable that
I found the one in the Museum's radio had been removed and replaced with
a Germanium Diode in an earlier repair.
I'm often asked what sort of things a restoration of an old radio like
this involves, so I'll try and give a brief description. The first
decision was how thoroughly to restore it. As so much was dirty and
damaged, I decided to aim to restore it so that it looked like it might
have done when it was in use, since there are far too many old radios
sitting in corners of museums looking so decrepid that I have overhead
children looking at such sets, and wondering with horror how their
grandparents could possibly have owned such a thing. The finish on
the case was so badly damaged there was nothing to be gained in trying
to preserve it. The first stage was to separate the two jobs, the case
and the chassis. The case was cleaned, sanded, treated with woodworm
erradicator and then varnished; the goal being to present the radio as
it might have looked when it was in use.
The chassis needed more work; a cursory inspection showed that the
wiring was not how it should have been according to the circuit
diagram (this simple check was made more difficult by all of the
manufacturers' variants). However all of the parts other than the
Wesector seemed present. I therefore stripped all parts off the chassis
and cleaned everything in solvent cleaners. Components removed were
tested individually. This showed that most of them were fine, but the
electrolytic smoothing capacitors were faulty (leaky). These were large
aluminum cans, three inches long, and modern equivalents were about half
an inch long. So that the underchassis looked as close as possible to
what it should, I removed the old contents and fitted the new capacitors
inside, which was a time consuming and smelly process!
The first assembly I started work on was the rectifier, which thanks to
the existence of the two versions (battery and mains) is a separate unit
sitting on top of the mains transformer. This arced when switched on
and it turned out that the valve holder was no use as the paxolin had
carbonized. Asking round a number of friends produced one new in bag
from the contents of his voluminous garage. Unfortunately this didn't
fit as was and I had to turn special spacers on the lathe in the museum's
workshop to correct for its positioning. With this unit working and
tested for insulation resistance I was able to turn to the main chassis.
One of the oscillator coils was open circuit, so by carefully melting
out the wax in the oven I was able to remove the old wire and rewind
the coil using litz wire.
After checking all the parts I commenced the slow reassembly working from
a handmade drawing of the underchassis and the original circuit diagram.
I had made the decision as a safety precaution to rewire using modern PVC
coated wire as 50 year old cloth insulated wire can present a fire hazard.
One of the difficulties which would have been presented when working
with a radio like this fifty years ago is that being a superhetrodyne
design, unless it is correctly aligned then it won't work at all.
Alignment could be a fiddly procedure with early test equipment -- the
most a radio repair shop might have possessed would be an AVOmeter and
signal generator. The now ubiquitous oscilloscope was only to be found
in the larger shops, and its use even there was uncertain, one handbook
of the time (it may be coincidental but I found this volume for a dollar
in a second hand bookstore in Hollywood!) encouraged the shop owner to
put it into the shop window and have someone pretend to be using it all
the time to attract customers to bring in the sets for a ``tune-up''.
While I have a 1940s signal generator (AVO Allwave Oscillator) to hand,
there seemed no need to take the difficult route, so I aligned the set
using a spectrum analyser!
On bringing up power to the stages individually (using an isolating
transformer!), the oscillator wouldn't oscillate, but that was rapidly
rectified by switching the connections on the coil (to correct the phase)
and the set was working receiving stations. Sadly not the stations
of yesterday though the sound has a similar mellowness due to the poor
frequency response of the set!