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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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7th Jun 2021, 12:39 pm | #21 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
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Re: Cracked outer glass on twin panel CRTs
I agree John that heating is not good. Unequal expansion could easily cause an implosion.
I'm surprised these tubes have only a cracked faceplate. They've been stored in a shed with summer temperatures of 40c cold as low as -15c and often sudden changes.
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7th Jun 2021, 12:41 pm | #22 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: Cracked outer glass on twin panel CRTs
Quote:
I wouldn't even attempt to remove a cracked face plate. Something is likely to give and I wouldn't want to be anywhere near at the time!
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7th Jun 2021, 12:49 pm | #23 |
Hexode
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
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Re: Cracked outer glass on twin panel CRTs
Heating tubes when in production and re-building was part of the process.
What's so strange about that? Ageing of the tube, perhaps, but it's 100% enclosed. The guys on Youtube with hot air guns are the ones that terrify me! An oven raises the temperature fairly uniformly, the hot air gun is very localised and causes differential expansion - now that is a worry, especially as it's not enclosed. The method works - I'll admit that it sounds crazy - but I'll post some pictures of the results when I have I have a moment. There have been no failures and no disasters but that's admittedly only with relatively small tubes. Refitting is the easy bit with optical grade silicone. It can be done. Usual H&S warnings here . . . Best regards, Paul M |
7th Jun 2021, 2:13 pm | #24 |
Hexode
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
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Re: Cracked outer glass on twin panel CRTs
As promised, some pics of the oven-ready CRTs.
OK, I'm an engineer not a photographer First up is a 9" Conrac (possibly an RCA CRT) and second up a 14" Conrac. Both with curved face-plates. Third is a 7" flat face CRT for a broadcast camera viewfinder. Many are going like this and the final pic is of a really bad example showing a re-gunned Central Tubes unit. Perhaps they should have been replacing the faceplates after-all! To be fair, many others from several manufacturers are going the same way but not all - some makes are still perfect. This is just to show that the technique works. Never had a failure, but one day there may be - it's about risk management. I'm also not saying that it should be tried on rare/valuable/large/fragile examples, but it is a valid technique and the tubes are contained within the oven. An industrial oven would, in any case, be needed for larger sizes. Usual H&S disclaimers - own risk etc. Best regards, Paul M |