Ultra model 66 1935

This little old lady came in from a local auction company. Must have been brought over to Spain many years ago! Too original and in general good condition not to bring back to life. Goes without saying, all paper capacitors had to be changed as these had turned into 100K Ohm resistors. The HT filter (that´s a modern term isn’t it?? I stick with reservoir I think) capacitor can must be left in place with some new ones tuck out of sight. One day will drill out the contents of the old can and tuck the new ones inside. Always concerns me when you see an energized loudspeaker, but in this case the field coil was intact. So, a power up keeping an eye on the angry pixie current meter. Had some sort of crackle but not much else. The set is quite a simple design, none of this fancy superhet business, oh no, straight forward TRF! Wondered why I couldn’t find the local oscillator signal, look at the diagram?? Checked the HT and was about correct so that was good.  The volume is controlled by grounding the cathode of the RF amplifier valve! A scope showed I was getting some audio racket at the detector, valve 2, an AC/s2. Was worried the output valve AC2.pen had suffered as a result of a life of hard bias. Waving an AVO around the grid of the output valve brought a splash of audio for a second or so. Now then, there is a centre tapped double resistor, 2 x 138 ohms which forms part of the cathode and screen grid potential divider. One part was open circuit, replacing that, result happiness. 85 years young, all the original valves seemed to test ok! Imagine what this set has delivered to it’s owners? Mr. Chamberlain, Churchill. Anyway, all working well and set for another 85 years one hopes….

 

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