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I'm not sure at this stage whether
the case was bought ready-made, or perhaps as a set of parts
or whether it was constructed by the builder of the set, who,
if he did design and make the case must have obviously been a
dab hand at woodwork.The finish of the plywood surface is utilitarian
and he didn't bother to french polish it. The paint finish is
now peeling off and the grain of the wood is very pronounced.
The radio front panel is made from plywood, rather than ebonite,
which may have been going out of fashion when this set was made.
The terminal panels which are made from an early form of ebonite
and are almost certainly the oldest parts of the set and maybe
one of these (the second from the right) dates from WW1. |
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There are three valves in this model.
On the left a Mullard PM2A B4 triode, above it another B4 triode,
a Mullard PM2DX and to the right a Cossor
B4-based 215SG tetrode. All have 2 volt filaments and all
are marked "BVA". You can maybe also identify the following
parts... a Telsen interstage transformer, a couple of HF chokes,
the brown dog-bone shape made by Telsen (known as a "Binocular"
choke) and the circular black one made by Lewcos, and a couple
of fixed condensers, a 1uF which tested as 1.25uF with an ESR
of 0.04 ohms which is remarkably good and a brown bakelite Telsen
mica condenser whose value is not visible. On the front panel
is mounted... A pair of Ormond tuning condensers (one brass and
the other aluminium), a JB aerial tuning condenser, a pair of
solid dielectric variable condensers.. one 0.0001uF made by Telsen
and the other an anonymous 0.00015uF which is foreign made. The
tuning coils were made by Colvern. |
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The grid-bias battery was usually
clamped onto the baseboard and is now missing, together with
its leads. The front end of the set below uses a screen grid
valve and, to help with stability, a copper sheet has been tacked
onto the plywood baseboard. The vertical panel is steel rather
than brass so is now going rather rusty. |
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The back end of the set has an RF
stage with reaction so that with its pair of RF stages, the user
would have to keep the pair of tuning condensers in track. The
coils used are commercial types so would have been reasonably
well matched, resulting in the dial readings being about the
same for any given station. Two sets of coil windings are provided,
giving reception on medium and long waves. With all these types
of sets, usually constructed between about 1928 and 1932, a record
needed to be kept showing dial settings for ones favourite stations. |
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This example of the ST300 includes
an integral loudspeaker (incidentally the designation "ST300"
is said to relate to the number of valves.. times 100 of course!)
Many people stretched their funds to the utmost to buy the basic
kit and made do with their crystal-set headphones. The constructor
of this one clearly planned his to include an early moving coil
permanent magnet loudspeaker. Once I'd cleaned the label I could
see it read Celestion Model 9 PPM. |
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Not many resistors....two
are shown below. Different voltages, rather than being defined
by resistors as would be the case nowadays, are provided by the
HT battery which would usually supply two or three voltages for
the valves. |
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A rather odd condenser, being from
1946 and thus implying the old receiver was working maybe even
in the 1950s or later. Alas the newer electrolytic marked 2uF
275 vw measued only 1uF with an ESR of greater than 20 ohms which
makes it pretty poor. |
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Summarising my findings; this set
should be easily restorable because it's complete and shows signs
of being rejuvenated either in the late 1940s or 1950s. Below
is a rather glowing advertisement from 1931 for the RF valve
used in the ST300. |
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