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1936 Baird T5 TV Receiver restoration

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Nuvistor
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@till Sorry to hear that David after all the work.

Frank

 
Posted : 05/02/2024 10:36 pm
Till Eulenspiegel
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Hi Frank,  the only course of of action now is to modify the Baird T5 to accept the 15" Cossor type 65K CRT. The Baird T23 in my collection was modified by the factory to employ the tube made by the rival manufacturer. Of course the Cossor CRT is not a drop-in replacement. For starters a metal adaptor plate must be made for the differently shaped CRT bulb. The frame oscillator transformer with it's extending pole pieces and the focus magnet will have to be raised up 5 inches or so to accommodate the shorter CRT.  So now I have task of dismantling the T23 in order to measure up the positions of the new components needed to completer the Baird T5 job. 

Worth mentioning the Baird T23 might have been subject to a works CRT replacement but it was one the roughest conversion jobs I've ever seen.

Till Eulenspiegel.

 
Posted : 06/02/2024 3:58 pm
Nuvistor reacted
Cathovisor
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Posted by: @till

The Baird T23 in my collection was modified by the factory to employ the tube made by the rival manufacturer.

It wasn't unusual to see Cossor valves specified in certain positions pre-war Bush radios though - quite often the Cossor MVS/PENB would be used as an RF amplifier and there were several other examples to be seen. I'm sure the 41STH makes an appearance too.

 
Posted : 06/02/2024 6:13 pm
Till Eulenspiegel
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Today, I gave the Cathovisor CRT another blast of EHT. Once again this action seems to have done the trick. But how long will the filament hold up? 

Till Eulenspiegel.

 
Posted : 09/02/2024 9:35 pm
irob2345
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Time will tell...

The one I did recently, that would go O/C as it was warming up, then cycle on and off (like an old-fashioned Xmas tree lamp), responded to 250 volts DC, current limited to the 600mA heater rating using two huge incandescent lamps.

The first two times we tried it, it failed again after a few minutes, then after a day switched off. So we hit it again with 50% more current in a kill-or-cure attempt and so far it has held up for over a month.

So it does seem to matter how much energy you can put into the welding arc.

I wonder if it need to be DC? We used the TV's HT supply (transformer sourced voltage doubler) but you'll need a few amps, so maybe direct mains in series with 2 or 3 amps worth of lamps (bathroom heat lamps?) would do the trick.

I think, if it fails again, what do you have to lose by trying a more aggressive approach?

 
Posted : 09/02/2024 10:08 pm
Till Eulenspiegel
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This Cossor 65K will go into the Baird T5 after a number of reversible modifications have been carried out.

Cossor 3265 CRT

Till Eulenspiegel.

 
Posted : 22/02/2024 10:19 pm
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