Components used in the Philips 2514

 Most of the resistors used in the set are wirewound in an open fashion. Formers are either paxolin or a type of perspex, large ones mounted on clips whilst smaller devices are suspended in the wiring. Later forms of construction used carbon rods which suffer from changing values through an ageing process whilst these older wirewound types are probably as good as the day they were made. Most of the capacitors are in blocks. Coils are high Q types ("Q" standing for quality, and is a measure of its low resistance to RF currents), either basket wound or large diameter in order to get the most gain from the design.

 This view shows part of the coil pack and the detector (second stage) tuning condenser. The two tuning condensers used in the set are identical and have sizeable brass components and a cleverly designed method of construction. Unfortunately the set had a nasty fault, typically found in most early examples of mass produced items before bugs have been ironed out. When I say "early" I don't mean in terms of the age of the radio I mean early in terms of its production run. When I worked in a large engineering business I was "Configuration Manager" and had to sort out problems such as these. Whenever a collection of components is assembled the tolerancing aspects usually make themselves known during the first proper production run. Holes are in the wrong place, metal bits are too big to fit in holes and of course there are electronic problems as well. Everything is made to a tolerance which may be measured in plus or minus thousandths of an inch, millimetres, picofarads or ohms. The more precise the tolerance the more expensive a component. In a cheap mass produced assembly tolerances are therefore quite broad and when they work against each other the bits don't fit together properly and the production line grinds to a halt, or the inspection people get a bit lax - as in the case of this radio!

In this example the tuning dial which fits on the rear of the tuning condenser locates with a brass device which is turned by the knob on the end panel. There is a spring which fits concentrically inside the spindle, on which the knob is fixed, which tensions the brass fitting so that it engages with some degree of friction within a slot running around the periphery of the tuning dial. Normally, rotating the knob turns the tuning condenser, with a step-down ratio of maybe 20:1, and action is perfectly smooth. However in the case of one of these tuning condensers, tolerancing was such that the dial rim, not just the edges of the slot, was permanently in contact with the brass device. This acted like a brake on the slow motion operation and imperfections on the rim affected the friction. Over the years, through repeated use, patches of wear appeared on the rim and caused the tuning to be not only very very stiff but very lumpy as well. Over all, operation of the knob felt very rough and extremely stiff indeed. Strangely the owner must have never bothered to complain, or if he did was fobbed off. Perhaps he didn't realise that the nice smooth control on the right was supposed to be exactly the same as the one on the left.

I removed the tuning condenser and carefully filed a few thou from the rim of the dial. Operation of both tuning knobs is now smooth..after a wait of 71 years!

 This view shows the variometer used for adjusting coupling (and hence positive feedback) between the first and second set of tuned circuits. The adjustment is carried out by turning a knob connected to the coil in the centre of the outer basketweave coil. The coil connections are made via two hairsprings like that on the balance wheel of a clock. The techniques used in this set had probably reached the peak of design perfection by the time this receiver was made but superhet receivers took over shortly afterwards and the TRF design with all its clever techniques was abandoned.

The introduction of the superhet must have significantly increased the attraction of radio to the masses as it became essentially "non-technical". As far as a user was concerned, tuning was now transformed to merely setting a knob to the place on the dial showing the station name instead of searching, listening to shrieks and howls, lots of knob twiddling and much readjustment as things drifted when the set warmed up....
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