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Old 6th Sep 2017, 7:33 pm   #41
FERNSEH
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Default Re: Gec 12" bt5144.

The replacement mains dropper resistor was fitted today using the specially made adaptor plate.
The resistor is dated 7312 and the values of the sections are:
17 + 17 + 17 + 118 + 67 + 67 ohms. Can anyone recognise which set it was originally designed for? Obviously it was a monochrome set.

DFWB.
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Old 7th Sep 2017, 8:02 am   #42
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Default Re: Gec 12" bt5144.

I think it was for the Sobell/GEC 1018 series. It just rings a bell. John.
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Old 7th Sep 2017, 9:00 pm   #43
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Default Re: Gec 12" bt5144.

Quote HKS:
"I think it was for the Sobell/GEC 1018 series. It just rings a bell." John.

Hi John, checked the mains dropper resistor values in the 1018 circuit diagram, it's not that one.

Today, I attempted to install the chassis into the cabinet but it was found the mask doesn't fit properly. It turns out it was made for a CRT with a more spherical faceplate. The GEC CR tube faceplate is almost flat.
A new mask will be made for this set.

DFWB.
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Old 8th Sep 2017, 10:30 am   #44
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Default Re: Gec 12" bt5144.

The new CRT mask will be made by using 1.8mm plywood.
Pictures of the one I made for the GEC BT9121 pre-war TV set.

DFWB.
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Old 8th Sep 2017, 12:12 pm   #45
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Default Re: Gec 12" bt5144.

The new plywood CRT mask is test fitted in the cabinet.

DFWB.
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Old 8th Sep 2017, 5:04 pm   #46
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Default Re: Gec 12" bt5144.

That first mask looks like a masterpiece of cornflakes-box engineering (I'm not taking the mick, I mean it - I get through loads of cardboard in the shed, and have even had someone laser-cut something in steel for me without a drawing, based on a carefully-made cardboard template). It must have been really tricky to fit the template into the aperture and at the same time track the curvature on the face of the tube - well done!
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Old 9th Sep 2017, 9:53 am   #47
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Default Re: Gec 12" bt5144.

Hi Mark,
the construction of the mask for the pre-war GEC TV was a time consuming affair and was as you suggested was a matter of making templates and cutting bits off until a satisfactory shape was achieved. The only problem with that mask is you have to watch the picture dead ahead because the screen is set back quite a lot.
The GEC BT5144 CRT mask is a much easier construction proposition thanks to the almost flat tube faceplate.
Other CRTs that that are good for easy mask construction are the 14" rectangular types such as the MW36-24 and AW36-20. In fact if you think about the Pye VT4 the tube was simply fitted into a wooden cradle. Push through presentation was also an easy solution to mount the CRT and was favoured by Peto-Scott and Bush.

DFWB.

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Old 12th Sep 2017, 6:23 pm   #48
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Default Re: Gec 12" bt5144.

Hi David,
I had a look at my spare mask and it is the same if not worse than yours, so making a wooden one was the right way to go...
Interestingly my mask is also curved. I think the set it came from (a BT4541 console) was fitted with a Mullard tube.

Cheers
Andy
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Old 12th Sep 2017, 7:08 pm   #49
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Default Re: Gec 12" bt5144.

Hi Andy,
when I return to the workshop I'll take a picture of the new plywood mask which is now fitted in the set. It just needs painting to finish the job.
Cossor had the right idea on how to make a CRT mask. The company used metal masks in the 10" 916 and 12" 927 models.

DFWB.
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Old 12th Sep 2017, 7:29 pm   #50
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Default Re: Gec 12" bt5144.

Like John I guessed the GEC 2018 series myself for the dropper!
Perhaps a Rank model or Plessey as a guess?

The set's looking great.
Cheers
Brian
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Old 12th Sep 2017, 8:00 pm   #51
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Default Re: Gec 12" bt5144.

Hi Brian,
it's a bit of a mystery for which set the mains dropper was made for.
One thing is certain it's a perfect replacement for the GEC BT5144.

DFWB.
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Old 26th Sep 2017, 10:43 am   #52
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Default Re: Gec 12" bt5144.

The CRT mask has been painted "Old English White" the colour you see on BMW Minis. Mask has been made to resemble the original so has an aspect radio of 5:4, 10 X 8 inches.

DFWB.
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Old 26th Sep 2017, 11:02 am   #53
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Default Re: Gec 12" bt5144.

Well done David this is looking very good!! I may have to do similar with my BT2147 if I can't salvage the original rubber mask. Great work!

Matt

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Old 26th Sep 2017, 11:05 am   #54
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Default Re: Gec 12" bt5144.

That mask looks good David,
Very good save there.

Marc.
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Old 26th Sep 2017, 10:18 pm   #55
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Default Re: Gec 12" bt5144.

This is an excellent set. Displays the 2.5Mc/s bars clearly, 3Mc/s fuzzy.

DFWB.
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Old 27th Sep 2017, 8:04 am   #56
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Default Re: Gec 12" bt5144.

That looks really good David! Are you up for making around 50 masks, all different of course.

GEC engineering at it's best. They did everything 'right'. The television and radio plant at Coventry was closed and passed to Sobell at Slough during the infamous 1961/62 slaughter. John.
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Old 27th Sep 2017, 10:26 am   #57
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Default Re: Gec 12" bt5144.

Great restoration David - it looks lovely.
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Old 27th Sep 2017, 10:34 am   #58
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Default Re: Gec 12" bt5144.

Hi Tractionist, the cabinet is a simple box design but there is some clever detailing to enhance the appearance.
And I'm lucky with this set because the card back is in good condition.

Time to think about another GEC TV restoration.

DFWB.
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Old 27th Sep 2017, 7:33 pm   #59
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Default Re: Gec 12" bt5144.

There's something very endearing about it's 'unfussy' appearance ...... it's not 'plain' and it's certainly not 'ugly' too. It seems to convey 'no-nonsense functionality' .... and judging by it's restored performance - you've demonstrated that.

You were certainly lucky with the back cover !!!
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Old 28th Sep 2017, 6:08 am   #60
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Default Re: Gec 12" bt5144.

That's a very impressive CRT mask David!

Jac
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