G.E.C.  BC4070  

Finally in the GEC section we have the BC4070. GEC have abandoned the alternative model number altogether now for this receiver released in August 1939, just a few months before the outbreak of WWII. This receiver is a massive set that would have been positioned at the top of the (table) market. It is just over 2 foot long, 12" deep and 14" high. As can be seen it again featured pushbuttons, which were used to select the wavelength as well as selecting individual stations on the bands (not SW). 

 

The pushbutton operation method on this receiver was mechanical, whereby a rack and pinion type system on each pushbutton is mechanically linked to a spindle which physically rotates the tuning capacitor. This was not a particularly efficient system, and the metal parts were subject to wear and resulting reliability problems. The picture above middle shows a close up of the rack with its double row of teeth at the far end of the pushbutton, and the various linkages under the chassis. The receiver shown has not yet been restored, and it is obvious that it is the pushbutton unit that has let it down. The dial and cursor cord drives are broken, due to the strain they are put under as a pushbutton is pressed each time and the heavy tuning capacitor is "thrown" round to its new position. The other mechanisms of the pushbutton unit are also seized up, and some bent from the strain. Although purely mechanical this was quite an advanced system in that pressing a station pushbutton will automatically select the correct waveband too, if the receiver was not already on the suitable waveband. Another improvement over the preset trimmer method seen on the previous page (Touchtune 5) was that each medium wave station pushbutton can be used to select a station anywhere on the medium wave band, rather than a narrow frequency band defined by the range of the trimmer. A system was also incorporated whereby the amount of pressure to "push" a pushbutton, and the length of "pushing" travel was approximately the same irrespective of the required actual position of the tuning capacitor vanes. The pushbutton mechanism also provided the power on/off to the receiver (!) I think I will have to save further comment on the mechanical pushbutton tuning of this particular receiver until it is restored! 

Other items of interest on the receiver are the very pleasing louvres positioned either side of the large tuning scale. The loudspeaker is behind the louvres on the left hand side when looking from the front. Also provided is a magic eye, right in the middle of the cabinet at the top to indicate when a station had been accurately tuned in (one wonders how often that would be with those racks, discs and levers grinding about inside! The AVC also featured on the receiver would need to be working efficiently!) As well as general tuning scale illumination lamps further indication lamps were provided in the tuning window. So a top quality receiver, but that auto tuning mechanism does look a bit unpredictable. Valve line-up was KTW61, X65, KTW61, DL63, KT61, U50, Y63.

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