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Old 8th Apr 2019, 1:53 pm   #1
Chris55000
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Default British Prototype CTV Power Supply Circuits?

Hi!

The book on British Prototype CTV Theory I referred to early this morning suggests both mains–transformer circuits and series–run heaters were both in use in prototype receivers, but the circuit examples used showed a considerable number of valves in use, far too many to run in one series chain off the UK's 230/240V supply!

The book in question doesn't give the power supply circuits they used!

Can anyone point me in the direction of a Prototype CTV S.M. or set of circuit diagrams please ?

I have to confess I'm curious to know how the three British Makers, Bush, GEC & Murphy implemented the psu arrangements, both with regard to running innumerable heaters and providing 250V & 400V h.t. lines!

Chris Williams
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Old 8th Apr 2019, 6:16 pm   #2
Maarten
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Default Re: British Prototype CTV Power Supply Circuits?

I'm not sure about the British manufacturers, but Philips used multiple series chains.
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Old 8th Apr 2019, 8:19 pm   #3
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Default Re: British Prototype CTV Power Supply Circuits?

Power supply description for the Ekco CT100, courtesy of the old technology web site.
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Old 8th Apr 2019, 9:08 pm   #4
Chris55000
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Default Re: British Prototype CTV Power Supply Circuits?

Hi!

Any chance of some circuits anybody please?

(If the original material is fragmented or very difficult to read I'm more than happy to redraw!)

Chris Williams
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Old 8th Apr 2019, 10:14 pm   #5
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Default Re: British Prototype CTV Power Supply Circuits?

The 1956 Pye 405 line colour TV receiver employs a voltage doubler to supply the HT supply to the timebases. A HT voltage of 360V is realised by this arrangement. The two Westinghouse contact cooled metal rectifiers are housed in a separate sub-chassis. See attachment.
The original HT rectifiers failed a long time ago and have been replaced by a pair of 1N5408 silicon diodes. The 33ohm series resistors have failed and will be replaced by a pair of metal clad 25 watt resistors.
Because of the high valve count three separate heater chains are used which merge to supply the 0.9amp CRT heater.

DFWB.
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Old 9th Apr 2019, 8:50 am   #6
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Default Re: British Prototype CTV Power Supply Circuits?

The Philips projection receivers employed twin PZ30 rectifiers in a voltage doubler to obtain sufficient H.T. as did the Ultra 15" '70' series from 1950/51.

From 1950 -1956, for some strange reason, Mazda did not produce a range of television valves with common 300 m/a heaters. Instead they produced a mixed bag with 100m/a and 200m/a heaters wired in a series parallel arrangement, the whole lot then being connected in series with the 300m/a CRT! The popular makes to employ this arrangement were Ekco, Ultra, Murphy and quite a few more.

There were many odd power supplies arrangements in early receivers and those mentioned are only a few. John.
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