Eddystone Communications Receivers
The Eddystone Model 870A
I bought this very heavy all-metal receiver from a chap in
Christchurch. The model is the "A" version dating from
1955 and is not to be confused with the basic 870 which appeared
in 1948. The set is interesting as it's designed for use on AC
or DC mains and does not use an isolating transformer. I imagine
this "feature" must have resulted in many mishaps over
the years as the internal chassis can be at mains potential. A
study of the mechanics reveals that the outer case is isolated
from the inner chassis by numerous fibre washers and it's highly
unlikely that this type of design would pass muster now because
of todays much more stringent electrical safety standards.
The mains plug is a two pin affair which can easily be wrongly
wired or inserted and woe betide the careless engineer connecting
a signal generator ground connection to the chassis as there could
easily be 240 volts AC between them.
With the case removed, leaning one's hand on the chassis could
have unexpected results!
In my example the loudspeaker cone was damaged so I fitted
a nice new unit from an old Hitachi speaker. Unfortunately there
wasn't enough room for the magnet to fit easily so I bent part
of the chassis an eighth of an inch or so to make it fit. I then
realised that the speaker coil is at mains potential but the metal
speaker frame is at front panel potential. As there was only a
gnat's whisker space between the speaker frame and the chassis
the new arrangement was decidedly dodgy so I've resolved to repair
the old cone and refit the original speaker.
When I connected the receiver to the mains via an isolating
transformer it slowly came to life. Checking with my signal generator
revealed that the IF transformers weren't tuned too far out, and
after resetting the trimmers on each of the four bands, performance
was quite lively.
As the set has been stored in a damp environment the condition
of the case has deteriorated somewhat so proper restoration will
be shelved for the time being. To fix the paint finish to its
diecast front panel and case may require sandblasting before repainting.
General layout of the receiver.
This picture shows the clearance between the speaker magnet
and chassis between which may be 240 volts AC. Note the "Westector"
type HT rectifier and the ballast resistor for handling unwanted
heater voltage.
Showing the trimmer adjustment holes for the four bands and
stuck to the underside of the case is most of the original receipt
from Webbs Radio showing that in 1955 it cost about £15.
I paid £10 in July 2000 and at todays "values"
the original price would have been something like £300.
The Eddystone
S740
This
finely built receiver dates from 1950
Although Eddystone produced many designs
of receiver from before WWII to after the end of the valve era
all had the hallmark of good mechanical engineering design. All
had superb slow motion tuning dials with beautifully smooth flywheel
action. Not long after this model was produced the dial was redesigned
into a full-width horizontal shape. In use this is a more pleasing
type to use but was more complicated as it meant that a dial cord
and pulley system was needed as well as a geartrain. The fine-division
logging scale in the newer version was moved to a more convenient
central position instead of being an offset dial as in this model
See more communications receivers>>