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.
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
MkIICompact little communications receiver with the usual high quality tuning arrangements always found on Eddystone sets.
It covers the following bands:
550-1500KHz; 1.5-3.5MHz; 3.5-8.5MHz; 8.5-18MHz and 18-30MHz
with Filter, BFO and AGC switch to aid reception
