An early Eddystone receiver,
the S640
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Below: a view through
the inspection cover for access to the nine valves. The case
is secured by four large screws and fits tightly to the front
panel moulding and pulls off to permit access to the underside
of the chassis. The receiver was designed specifically for the
shortwave listener or radio ham and as such receives only frequencies
from 1.7 to 32MHz. Two tuning condensers are fitted. Once the
main tuner has been set to a particular band the fine tuner is
then used for bandspreading. |
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Very apparent is a heavy
build-up of dirt and some corrosion although the chassis is heavily
plated and should clean up. Cans appear to be made of plated
brass and again, should clean up but with a lot of effort. The
coil enclosure is made of an aluminium alloy and will be pitted.
The set is an AC model unlike many Edystone sets which are AC/DC.
The octal sockets on the rear of the chassis support an external
S-meter and feed from an alternative external power supply. |
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Nine valve line-up: RF amplifier
EF39 (V1), frequency changer 6K8 (V2), first IF amplifier EF39
(V3), second IF amplifier EF39 (V4), detector/avc and audio amplifier
6Q7 (V5), audio output 6V6 (V6), noise limiter EB34 (V8), BFO
EF39 (V9) and HT rectifier 6X5 (V7). |
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Above: A very tidy layout
of the RF coils with trimmers and coils easy to adjust.
Ranges covered are:
32 -12.6 Mc/s, 12.6 - 4.5 Mc/s
and 4.5 - 1.7 Mc/s
Below: Either side of the coil
pack enclosure are the these two areas of circuitry, the IF amplifier
and the power supply plus BFO. |
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Click the circuit diagram to
see a much clearer PDF version |
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A lot of work will be
necessary to restore this old receiver dating from 1947, mainly
cleaning the chassis, the front panel (which will need repainting),
the bezel which might need replacing. The case is also in poor
shape and the main tuning dial needs new string. Most of the
old condensers will need replacing and probably several resistors. |
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