The Ekco M23 All Electric Receiver was one of the first to use a moulded "bakelite" cabinet, designed by J.K. White. It was released in 1932, and cost Ł17 17s. Electronically it is a fairly conventional TRF circuit using a Westinghouse metal rectifier for HT supplies. The valves are neatly grouped at the back for easy access.
The valve line-up is:
AC/SG RF amplifier
The set employs a separate tuning trimmer and an aerial trimmer for volume control. Capacitative reaction is applied to the detector. The HF valve biasing arrangements are rather unusual, and consequently the earthy ends of the HF circuits (including the tuning capacitor frame) are not at chassis potential.
The detector is transformer coupled to the directly heated output pentode. A permanent magnet loudspeaker is used, and the HT is smoothed by a tapped choke in the HT negative return. The tapping provides bias for the pentode, and this arrangement results in the can of the electrolytic smoothing capacitor not being at chassis potential.
There is thus a lot of exposed metalwork in this set at differing potentials!
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