Philips Type 745A Receiver, 1936

 This AC mains receiver looks new but is in fact over 80 years old as I write this on New Years Day 2017.

 
 The set is a superhet having an IF of 128Kc/s and uses the following valves: Frequency changer FC4 (octode), IF amplifier VP4B (variable mu pentode), Detector and AVC 2D4A (double diode) and audio output Pen.A4 (pentode). The HT rectifier valve is an 1821. Unlike many sets there is no separate AF amplifier because all the audio gain is managed by the pentode output valve. The loudspeaker is a permanent magnet type rather than the popular mains energised type found in the majority of sets of this period. Below: even the valves look brand new!

 

 Wavebands covered are Long 725 to 2000 metres, Medium 198 to 595 metres and Short 16.5 to 51 metres

 

 

 
   These are the various labels attached to the set

 Below, the unusual mains connector which is only removable once all the clips are opened and the rear cover detached.

 

 
 In the first picture of the set you'll see the dial, which has a plastic front, set into a bakelite surround, which for some reason which is not clear to me, can be tilted upwards. This feature required a problem to be overcome, namely how to transfer the movement of the tuning control and tuning condenser position to be copied to the dial pointer. In fact this is achieved by a method employed by Philips in a great many of their receivers made up to the end of the valve era in the late 1960s which is by using Bowden cables. The Bowden cable is a very strong wire in a sheath and is much superior to the usual cotton dial cord and has a number of advantages, chiefly being able to transfer movement forwards or backwards with no slackness and without a complicated arrangement of pulleys and springs. The key disadvantage is if the wire breaks or if one of the fittings becomes damaged. I've seen some Philips sets arrive in the workshop with a tangled mess of wire due to something seizing or misalignment. The tightness of the Bowden wire means that everything needs to be lined up precisely otherwise the wire can ride up a pulley and slip off. A tuning condenser is often mounted on three or four rubber bushes and these can perish allowing the pulley on the condenser spindle to move around. If the movement is too great the wire (or dial cord) rides up the edge of the pulley and slips off. This is something that needs to be checked once a chassis has been removed from an old set.
 

 Finally, I tested the set using a wire aerial and it worked OK. Then, having noticed the "Mains Aerial Switch" I tried this and it was just as good, if not better than the wire. Back in the 1950s my father bought a "wonder aerial" which was a black cylinder about 4 inches long by 2 inches diameter. It had three leads: connection to set, AC mains and earth. It wasn't as good as our long wire and made reception rather crackly.

The back of the set is held on by rotary clips which are really easy to turn thus allowing it to be released very easily although the mains plug does need jiggling quite a bit to pull off.

Click to see the manufacturers repair manual

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