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Old 11th Dec 2016, 10:06 pm   #12
FERNSEH
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Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,913
Default Re: A scary Baird T23.

Hi Andy,
the date codes on many of the components in the T23 indicate it was made in 1938. All the other T23 sets still in existence are also fitted with the Cossor type 65K CRT. All evidence of the conversion of the set to accommodate the shorter tube shows it was done in the factory. However, the execution of the conversion work appears to be have done in a very sloppy manner.
It's all very strange because Baird Television Limited owned the Cathodevisor CRT works. Most likely Cossor offered the tubes at lower price than BTL tubes works could offer them. The Cossor 65K must have been cheap because you have to factor in the cost of the additional components required to install the Cossor tube.
The 65K CRT was also installed in the well known Cossor 1210 TV set which was made at the same time as the T23.
The timebase unit in the T23 is similar to the 1936 model T5 save for the addition of an interlace diode. Some sets use a diode connected Mazda AC/HL which can be replaced with a V914 double-diode. The best power triodes for the timebase oscillators has been proven to be the Cossor 41MP.
The Mullard TT4 and Osram ML4 will work OK as replacements.

DFWB.
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