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Old 19th Nov 2021, 10:09 pm   #1
Niechcial,Steve
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Default CRT Identification Please

I have a 14 inch rectangular crt. Externally it looks very much like the MW 36-44 with the same valve base except that the base material is metal rather than plastic. Internally it looks also to be a simple triode gun. It differs from the MW 36-44 though in that its gun is straight down the axis of the neck. In other words, it doesn't look like it's designed for an ion trap. Any ideas please? Thanks.
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Old 19th Nov 2021, 10:22 pm   #2
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Default Re: CRT Identification Please

Possibly a GEC with a triode gun assembly. Made about 1953.

DFWB.
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Old 19th Nov 2021, 10:27 pm   #3
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Default Re: CRT Identification Please

MW36-67?

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Old 19th Nov 2021, 10:57 pm   #4
Niechcial,Steve
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Default Re: CRT Identification Please

Thanks David and Adrian. I can't see anything about MW36-67 online. Can you point me to a data sheet please?
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Old 19th Nov 2021, 11:05 pm   #5
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Default Re: CRT Identification Please

On the frank.pocnet.net site
https://frank.pocnet.net/sheets/030/m/MW36-67.pdf

Also an advert in Wireless World November 1956 pages 80 and 81
https://worldradiohistory.com/UK/Wir...6-11-S-OCR.pdf

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Old 19th Nov 2021, 11:17 pm   #6
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Default Re: CRT Identification Please

GEC 7203A? Advert in the July 1956 Practical Television magazine.

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Old 19th Nov 2021, 11:24 pm   #7
Niechcial,Steve
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Default Re: CRT Identification Please

Thanks. I see both suggestions are aluminised non-ion trap tubes, so I guess it could be either
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Old 20th Nov 2021, 11:13 am   #8
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Default Re: CRT Identification Please

Hello Steve, I would go with David here. It could of course be the monitor tube but they must be very rare.
The 7203A is an excellent tube, pin sharp with excellent contrast as fitted in my GEC BT1746 from 1956. The pic needed a bit of adjustment shift wise but will give some idea.
It will replace the MW36-24/44 but being a triode the focus magnet may not be strong enough. John.
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Old 20th Nov 2021, 10:19 pm   #9
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Default Re: CRT Identification Please

Thanks John. Thanks also Adrian for that Wireless World attachment which is well worth reading in itself.
I think the metal base surround makes it more likely to be the GEC tube too. I had thought that my original tube had a partial heater short (which they are prone to), but on checking with a separate power supply, it was drawing the correct 0.3 amps at 6.3 volts. I gave it a boost with my BK and it's come up very well. I will see if it survives, and if not, fit the mystery tube. Thanks again all for the help. Stephen
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Old 22nd Nov 2021, 10:33 am   #10
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Default Re: CRT Identification Please

First thing I check for in such a case is whether there's a Mullard-like manufacturing code on it. Either on the socket or in white ink somewhere on the tube.
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Old 22nd Nov 2021, 11:19 am   #11
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Default Re: CRT Identification Please

Hello Maarten,
As you can see from the picture this is definitely a GEC manufactured tube type 7203A.
GEC manufactured their own triode aluminised tubes until around 1958. They then employed Mazda [EDISWAN] to supply them with their range of tubes with GEC labels. In fact the labels were identical to the Mazda with just the name changed.
GEC did use a few MW36-24 Mullard tubes in the 1954 model BT1746 but I think this was due to supply shortages. GEC produced triode tubes of very high quality but this put them in a difficult position when it came to the replacement market due to the increased focus field needed for triode tubes. This was also the problem with FERRANTI who followed a similar path.
The early Mullard 14" rectangular tubes in the UK were the MW36-22, MW36-24 and the last magnetic focus MW36-44. The MW36-22 did not have a grey glass filter screen and is very rarely seen. As far as I am aware Mullard never produced a triode tube for domestic use in the UK and were very late in aluminising generally, the MW53-20 and AW36-20 being examples. Regards, John.
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Old 23rd Nov 2021, 12:53 pm   #12
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I didn't quite get what was meant with a metal base, but seeing this picture I wouldn't even go looking for Philips codes. I wasn't sure of possible early Mullard developments with aluminisation or triode guns, but clearly not the case.
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