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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 20th Feb 2018, 5:49 pm   #1
Orakle42
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Default Transformer Identification

I recently found this item festering in the back of a store cupboard and after"conditioning" it in an airing cupboard for a week became intriged as to its origin. It is obviously OLD and dates from the 4 Volt heater era. The attached picture shows the size and terminal layout together with measured voltage and resistance readings. Although appearing to be of commercial manufacture (its clearly marked ULTRA) the "Termination" on the 4volt windings are just wire ends (12g & 16g) so are obviously for a heavy heater current. I am intrigued by the use of the 3.5v winding as the only devices I can find with <4 volt heaters are HW rectifiers or CRT's. Does anybody have a clue regarding set type or other application?
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Old 20th Feb 2018, 7:42 pm   #2
Cobaltblue
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Default Re: Transformer Identification

Looks like a mains transformer from an ULTRA Radio Perhaps a model 25

25 is just a guess I am not going to look through all the Ultra sets of this period

The 3.5 V may be for the dial lights.

Cheers

Mike T
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Old 21st Feb 2018, 11:50 am   #3
boxdoctor
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Default Re: Transformer Identification

In view of the unusually high voltage of the H.T. winding, I would think it came from a largish P.A. amplifier, the two separate 4V windings being one for the directly-heated output valves, (PXxx?) and the other one for the heaters of the other low level stages. 3.5V may well be as Mike T. says, for dial lamps.
Looks hefty. Tony
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Old 21st Feb 2018, 4:24 pm   #4
Orakle42
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Default Re: Transformer Identification

Thank you Cobaltblue, the terminal layout is the correct match. I wonder if ULTRA used a standard terminal layout as the model 25 has a UU3 specified which only has a 250v anode rating. There are however several plug compatible devices with 4v heaters but higher anode voltages which takes us on to boxdoctors suggestion of a higher power device. I think the 3.5v supply for dial lamps is probably correct. It certainly looks capable of more "VA's" than the model 25 would require! Many thanks for your assistance.
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