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Old 5th Aug 2019, 4:48 pm   #1
crackle
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Default KB Pre-war Mirror lid TV

Has anyone ever seen one of these Pre-war KB tv's.
The photos were handed to me at Punnetts Town yesterday.
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There is also a typed article dated 30.6.1939 describing a table top TV based on the KB 760 wireless receiver.
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I would be interested if anyone has further details of either of these TV's.


Mike
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Old 5th Aug 2019, 5:59 pm   #2
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Default Re: KB Pre-war Miror lid TV

The K-B 790 Mirror Lid appears on Jon's site. Though the table model version does not. None are known to survive.

Steve
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Old 5th Aug 2019, 7:09 pm   #3
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Default Re: KB Pre-war Miror lid TV

Strangely KB don't appear to have had a stand at Radiolympia in 1939.

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Old 6th Aug 2019, 10:54 am   #4
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Default Re: KB Pre-war Miror lid TV

The K-B 780 direct-vision console appeared at the 1938 show - see HERE. It cost 44 guineas, including installation of a television aerial.

Peter, do you have brochures for the 1938 and 1939 Radiolympias?

Steve
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Old 6th Aug 2019, 11:27 am   #5
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Default Re: KB Pre-war Miror lid TV

Hi Steve,

No, I just looked up WW August 1939.
https://americanradiohistory.com/Arc...ld-1939-08.pdf

Peter
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Old 6th Aug 2019, 12:49 pm   #6
crackle
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Default Re: KB Pre-war Miror lid TV

Hi Steve
I have a copy of that same image of the KB 780, it must have come out of a paper or magazine or something.
My one states the "first monochrome Television" I assume this means it was KB's first monochrome TV, not the FIRST monochrome TV ever. The image I have came from what I believe was KB Museum at the STC factory here in Basildon.
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Old 6th Aug 2019, 1:48 pm   #7
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Default Re: KB Pre-war Miror lid TV

The KB780 and 90 [Mirror Lid] seem to utilise the same 12" CRT. The ad Mike has just put up stresses "direct" viewing to the screen on the 780. So these are pre-war sets and at least one has moved on from the long necked vertically mounted tube that necessitated a mirror reflection system in the first place.

Given this, I wonder why produce the mirror version at all? Maybe to have a larger product that would seem superior or was a Mirror System thought to be better for family viewing Basically if you now have a short 12" CRT available, why bother with a Mirror Reflection set up

Significantly only two Mirror Lid models were produced just after the War. One was very expensive [but I can't recall the make]. I have the other an Ekco TS48 [1946] I think] which definitely has a short CRT BUT mounted vertically and viewed in a mirror. It's been said, previously, that these perhaps represented a failure to catch up with new developments but the KB story may suggest otherwise. Maybe they were still hanging on to the notion that a Mirror Lid system aided group viewing? I recall that crowding around our set when I was a child [either a 9 or 12" table top] could have it's problems.

Dave W
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Old 6th Aug 2019, 2:33 pm   #8
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Default Re: KB Pre-war Mirror lid TV

Yes, the TSC48 must be the best known.
Decca had the "Beau Decca" in the late 1940s.

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Old 6th Aug 2019, 2:52 pm   #9
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Default Re: KB Pre-war Miror lid TV

Quote:
Originally Posted by dave walsh View Post
Basically if you now have a short 12" CRT available, why bother with a Mirror Reflection set up
Maybe they had a stock of mirror-lid cabinets which needed to be used-up?
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Old 6th Aug 2019, 4:56 pm   #10
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Default Re: KB Pre-war Mirror lid TV

At the time it might also have been thought there would be sales resistance to the unfamiliar presence of a 'bug eyed monster' screen in the polite drawing room. Whereas, the mirror lid discreetly tucked the screen away when not in use and the unit then looked like a more normal radiogram.

However, 'excessive cabinet depth due to the length of the tube' is the most common rationale heard against direct-vision. Having said that, there were direct-vision sets available from the very dawn of television. For example, the 1936 Marconiphone 704. Its screen only measures 7¾ x 6¼ inches, and it has an enormously deep cabinet, although it is a thing of great beauty. I've seen one! It would probably be best accommodated in the corner of a very large room.

Steve
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Old 6th Aug 2019, 5:09 pm   #11
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Default Re: KB Pre-war Mirror lid TV

Yes you might be right about the "bug eye" appearance Steve although there are Radio Sets that could be a bit frightening. I think the idea that something bigger could also be more discreet in some [with] drawing rooms carries weight, like the sets themselves! I take your point about sets with greater depth, rather than height, to accommodate a large neck but the crt in the Ekco is really quite short. The surplus cabinet notion is a possibility Nick but it's my impression that nobody was really ever in mass production with the "monstrous" Radiogram and TV Models-especially before the war! I already had an idea that no KB Mirror Lids had survived but that does surprise me a little. Anyone who could afford any sort of top line set at the time would be likely to have substantial premises and room to hang on to it. KB certainly had a name for high quality then and later [I have a colour TV from the sixties-with double Doors which must have cost a fortune] but perhaps they just didn't even make many of the 780 and 90 TV's if the market was slow and then the War started in September 39

Dave W

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Old 6th Aug 2019, 10:17 pm   #12
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Default Re: KB Pre-war Mirror lid TV

I'd certainly love to have sight of the circuit diagrams of these pre-war KB TV sets. By 1938 the owners of Kolster-Brandes, ST&C were making Brimar valves for use in the companies' radios and for sale to other manufactures. But I doubt if any special TV valves and CRTs were available from Brimar.
The attachment shows the table model TV set. I've indicated a valve which is most likely a Mazda SP41. The CRT might also be a Mazda. Kolster-Brandes' first post-war TV set, the CV40 employed a Mazda CRM121 CRT branded as Brimar.

DFWB.
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Old 7th Aug 2019, 7:11 am   #13
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Default Re: KB Pre-war Mirror lid TV

Hi David, I have a copy of a report issued by the "Television Laboratories, Sidcup, Kent" (or in other words KB) dated 30/6/1939, describing the method to be used for the "Table Model". This does have some schematics, but seem to be incomplete, there may be a page missing as I can see no CRT in the circuit, but lots of SP41's.
I will get around to scanning these and making them available, soon.

Mike

Last edited by crackle; 7th Aug 2019 at 7:39 am.
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Old 7th Aug 2019, 9:07 am   #14
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Default Re: KB Pre-war Mirror lid TV

Here is the document describing the table top TV. http://www.kbmuseum.org.uk/kb_servic...9_table_tv.pdf

Mike
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Old 7th Aug 2019, 10:40 am   #15
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Default Re: KB Pre-war Mirror lid TV

Thank you Mike.

Very interesting material!
And well spotted David: the SP41.

Jac
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Old 7th Aug 2019, 11:26 am   #16
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Default Re: KB Pre-war Mirror lid TV

Did the mirror magnify the image at all on these kind of sets?

This would be useful when screen sizes were small.
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Old 7th Aug 2019, 12:42 pm   #17
dave walsh
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Default Re: KB Pre-war Mirror lid TV

To my [very limited] knowledge there was no actual magnification although that would be possible with a slight curvature perhaps? Searching for evidence on this I found a thread from Roverp5B on here [2/2/14] concerning a 1986 Reproduction Mirror Lid TV [commemorating 50 years of the Ferguson Company]. However, David [Fernesh] identify's it as an Ultra Set [TX9 Chassis] as there were no Ferguson sets before WW2. Either way, there are photos at post 11* that appear to confirm no magnification effect re the Mirror.

Dave W
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Old 7th Aug 2019, 12:53 pm   #18
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Default Re: KB Pre-war Mirror lid TV

Hi Mike,
Thanks for posting up the information of the 9" KB table television.
It is a very well designed set, no short cuts. For example the Sound IF amplifier is a dual channel circuit having 6.5Mc/s for the TV and the standard radio IF of 465Kc/s. As I suggested the RF pentodes are Mazda SP61. Other functions are performed by Brimar valves. One surprise is the EHT rectifier, a Mullard HVR2 because STC did make a high voltage rectifier. It's used in the Baird T5.
The set has a good quality radio receiver so at least it was usable after the close down of the television service.

DFWB.
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Old 7th Aug 2019, 1:56 pm   #19
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Default Re: KB Pre-war Mirror lid TV

Hi Mike,
that's very interesting.
Yes, I'm sire the 12" sets will be the CRM121. That would make the 9" table set a CRM91 which has quite a wide deflection angle for the time.

The deep recess for the CRT in the mirror lid version suggests that the CRT is angled slightly from vertical, much like in the EKCO TSC48 - this really does suggest a CRM121 rather than something longer.

The circuit looks interesting with the shared IF sections for sound and radio, much like the HMV 905. DC restoration diode V8 is a nice touch.

Of course if you had a spare KB 760 radio chassis it could be the basis of a replica...

Cheers

Andy
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Old 7th Aug 2019, 3:11 pm   #20
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Default Re: KB Pre-war Mirror lid TV

Beery wrote: "Of course if you had a spare KB 760 radio chassis it could be the basis of a replica..."

Hi Andy,
We've got almost all the information we need.

DFWB.
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