One example is the Philips 207U from 1940's. It was in production for a long time. The tube lineup in the 1950's was UCH42, UF41, UBC41, UL41 and UY41, which were series-heated 100 mA tubes. The radio was advertised for AC and DC feed, 110-127 V and 220 V.
-- -TV
My grandmother had been living in an apartments building owned by the tram company. Apparently for historical reasons, the apartments were supplied with 220 Vdc. The radio consisted of two UCH21 triode heptodes, UL21 (IIRC) audio output pentode and UY1N half wave rectifier all driven by 100 mA series heater.
When she moved to a normal house about 1960, according to the legend, some modifications had to be made. However looking at the inside, I could not spot what modifications had been made, Perhaps the rectifier tube as shorted for 220 Vdc operations. No other transformers in that radio except the audio output transformer.
In Europe, the U-series (100 mA) series heated tubes were common for radio receivers. The P-series (300 mA) series heated tubes were used almost exclusively for TVs. In TVs, the anode voltage (170-200 V) was simply half way rectified from the 220/240 Vac mains.
Peak of 240v is about 330v. Valve rectifiers drop it but not by 130-160v.
NT
It was _half_wave_ rectifier followed by a CLC filter. You would need a huge capacitance in the C1 in the CLC filter to ride through both the last part of the active half wave, as well as the dead opposite half wave. This would not have been cost effective.
In addition, the tube rectifiers really do not like high peak currents that are generated by a big C1 and hence short conducting angle.In order to extend the conducting angle as large as possible on the active half wave, a small C1 is used with a large ripple voltage across C1. The L and C2 reduces the ripple voltage and averaging the DC voltage quite close to the RMS voltage.
The coil explains it. Extra points for making it saturable to improve voltage stability under load. A lot more common was a resistive dropper.
NT
In televisions there was a tapped high power resistor ("Mains Dropper") that would be set to the nominal mains supply voltage. (e.g. 240V, 220V, 200V...).
That would drop the remaining voltage. It would also go to the live end of the heater chain.
kevin
On Sunday, August 28, 2016 at 9:46:20 AM UTC-7, snipped-for-privacy@downunder.com ...
I don't remember seeing a choke after the rectifier in TVs, at least in '60's era sets.
Most had a tapped high-power resistor to drop the voltage to give the desired HT supply voltage and correct heater current.
kevin
I saw a swinging choke supply in a Zenith, but not in most TVs.
NT
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