UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 10th Jun 2018, 10:33 pm   #1
1100 man
Octode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default Twin-panel CRT's

Whilst poking about in odd corners of the forum, I have several times seen reference to 'twin panel' CRT's. I have not been able to discover exactly what these are, only that they were around in the early '60's and were favoured by KB!
I would be interested to know more about the construction of these- I assume there was some sort of bonded on plastic membrane?
Am I correct in thinking these were made obsolete by the introduction of the 'rimband' CRT?
Talking of these, presumably this was a pre- tensioned bonded on band designed to control the forces around the face of the tube? In the event of someone chucking a brick at the screen, the band would hold the glass together until the forces had been spent and stop glass flying everywhere?

Cheers
Nick
1100 man is offline  
Old 10th Jun 2018, 10:59 pm   #2
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: Twin-panel CRT's

Hi Nick,
It's an American idea first introduced in certain 21" roundie colour CRTs.
The first 23" "square corner" twin panel CRT was the imported type 23SP4 and was introduced in the UK the late summer of 1960. First TV set to be equipped with the new tube was the Pye V600A. The 23SP4 was also fitted in many BRC models, the first was the HMV model 1920.
The Brimar A47-13W twin panel CRT first appeared in a very early version of the KB VC1 series late 1962. The 23" tube was designated A59-13W.
The Mazda twin panel tubes were designated as CME1906 and CME2306.

DFWB.
FERNSEH is offline  
Old 11th Jun 2018, 6:54 pm   #3
Clydeuk
Hexode
 
Join Date: Mar 2012
Location: Liverpool, Merseyside, UK.
Posts: 453
Default Re: Twin-panel CRT's

If you look at Shango066 channel on youtube you can find a video where he cuts a rimband off with a grinder (evacuated CRT first) to see how much tension it's held in. It turned out to not be much at all.
Clydeuk is offline  
Old 11th Jun 2018, 9:03 pm   #4
slidertogrid
Octode
 
slidertogrid's Avatar
 
Join Date: Apr 2005
Location: Peterborough, Cambridgeshire, UK.
Posts: 1,897
Default Re: Twin-panel CRT's

There was no rimband on twin panel tubes. the screen was laminated with plastic. this made them very heavy for their size. the tube had moulded lugs on the corners of the screen to fix it to the cabinet, the laminations meant the screen would not shatter it would just crack if struck.

I had a KB vc1 which the screen had some signs of the layers de laminating it looked as if air had got between the layers. but not in the same way as the American tubes developed 'cataracts' in the centre of the screen. this looked like drips down the screen.

Rich.
__________________
The rotation of the earth really makes my day...
slidertogrid is offline  
Old 11th Jun 2018, 9:57 pm   #5
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
Default Re: Twin-panel CRT's

some oscilloscopes and other professional equipment with CRTs also used laminated faceplates which oxidises opaque (celluloid?) as it de-laminates.

The aforementioned shango066 youtuber has a vid of him removing a front faceplate, cleaning off the goo and replacing it using silicone sealant. He wears a full faceshield!
__________________
Kevin
McMurdo is offline  
Old 11th Jun 2018, 10:45 pm   #6
simpsons
Octode
 
Join Date: Feb 2007
Location: Harrow, London, UK.
Posts: 1,483
Default Re: Twin-panel CRT's

Sony 18" Trinitron and also the 32" Fine Pitch ,from a comment on an eBay advert, also have a bonded implosion guard. In the case of both the 18" 90 and 114 degree tubes, they can suffer from an ingress what must be moisture which results in black spots of mould forming around the circumference.

The eBay seller's whose HD Monitor suffered from this problem suggested that the implosion guard could be removed and cleaned. With my limited experience of the tube faceplate design, I couldn't see how this could be done.

Chris
simpsons is offline  
Old 11th Jun 2018, 11:39 pm   #7
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
Default Re: Twin-panel CRT's

here's the way shango066 does his

https://www.youtube.com/watch?v=32_qMSWEdjc
__________________
Kevin
McMurdo is offline  
Old 11th Jun 2018, 11:51 pm   #8
jay_oldstuff
Octode
 
jay_oldstuff's Avatar
 
Join Date: Jan 2005
Location: Hyde, Greater Manchester, UK.
Posts: 1,074
Default Re: Twin-panel CRT's

I have a KB (VC1 chassis) and my CRT is starting to delaminate, shame as the TV is absolutely mint otherwise. I beleve the phenomina is also starting to effect early computer monitors and terminals. I've seen at least one terminal made in the late 70's that the CRT is going the same way as my TV.
__________________
The light at the end of the tunnel is probably the headlight of an oncoming train
jay_oldstuff is offline  
Old 12th Jun 2018, 1:25 am   #9
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: Twin-panel CRT's

As a replacement for the twin panel A47-13W Mullard supplied the "Inckit". This consisted of an A47-26W rimband type of CRT and a specially made part to fill in the gap between the tube aperture and the periphery of the new CRT.

DFWB.
FERNSEH is offline  
Old 12th Jun 2018, 4:42 am   #10
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: Twin-panel CRT's

It appears that many computer terminals and monitors from the 1970s and early 1980s used twin-panel CRTs, and they do delaminate. This is a problem for me as several rare machines I have are affected.

I am worried about the suggestions to separate the panels, clean off the goo and re-seal. Surely unless the bond between the 2 glass panels is good, they will not act as laminated glass in the event of an implosion, and glass fragments would fly everywhere. I feel that a lot of the so-called 'repairs' are very dangerous as a result.

Actually, if the panels are delaminating, I guess they will not act as laminated glass if the CRT implodes. So the CRTs with the cloudy screens could be quite nasty.
TonyDuell is online now  
Old 12th Jun 2018, 7:58 am   #11
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Twin-panel CRT's

I thought, right or wrong, that the bonded faceplate only protected the area in front of the CRT, i.e. the viewer, a replacement for the old style seperate safety screen. The selling point was one less reflecting area and that no dust could get on the front of the CRT glass screen. For the set maker the cabinet design and TV construction were made much simpler.

The Rimband or Panarama type CRT were protected against implosion of the CRT whereas the bonded faceplate was not.

Of course if the laminate fails the CRT could fall out of its mounting blocks, the faceplate had the mounting lugs for the CRT.

Any thoughts, have I been under a misunderstanding all these years, very possibly.
__________________
Frank
Nuvistor is offline  
Old 12th Jun 2018, 8:49 am   #12
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Twin-panel CRT's

There was also the Fenbridge guard type protection, this was a flexible plastic sheet that was fitted to the front of the CRT, it was not bonded and had to be refitted to the replacement CRT.
I found these to be a PITA, experience helped but making sure there as no dust or air bubbles behind the guard was at time difficult. Warming the guard and CRT faceplate helped but they could be difficult on the larger CRT’s.
__________________
Frank
Nuvistor is offline  
Old 12th Jun 2018, 9:47 am   #13
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: Twin-panel CRT's

Yes Frank, and they turned a smokey green in a smokers house. Impossible to clean. John.
Heatercathodeshort is offline  
Old 12th Jun 2018, 11:12 am   #14
ctc15
Pentode
 
Join Date: Oct 2005
Location: Barnet, London, UK.
Posts: 167
Default Re: Twin-panel CRT's

https://www.vintage-radio.net/forum/...ighlight=ctc15
Hi Have a look at post 2 for a bad cataract.
Keith
ctc15 is offline  
Old 12th Jun 2018, 9:14 pm   #15
1100 man
Octode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default Re: Twin-panel CRT's

Well that's prompted some interesting comments! I watched Shangoo's video. I'm not sure I would have been too keen to heat the faceplate up with a hot air gun though . Once it had been removed and cleaned up, he just stuck it back on with a bead of silicon round the edge.
I think I would have to agree with Tony Duell about the reduced safety aspect. There must have been good reason why the manufacturers bonded it over the entire area rather then just round the edge.
Mind you, I think the chances of a tube from the '60's spontaneously imploding are very remote:- the danger is if the face of the tube gets hit.

Keith's link above looks like the same set that Shangoo was using in his video.

Cheers
Nick
1100 man is offline  
Old 12th Jun 2018, 9:28 pm   #16
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Twin-panel CRT's

The bonding was done at least for a couple reasons.
1. So the lugs at the corners at the protection would support the weight of the CRT on the rectangular CRTs. Not looked Shangoos videos but if they are the same I would not think the silicon would support the weight.
2. The idea was also to reduce reflections and not have 4 surfaces, by bonding there would only be 2 surfaces.

WW May 1962 has some information, it says page 71 but it’s the page after 240, it also seems that this bonding did provide protection against implosion from front and rear, I didn’t realise that, still I always treated CRTs with care.

https://www.americanradiohistory.com...ld-1962-05.pdf
__________________
Frank

Last edited by Nuvistor; 12th Jun 2018 at 9:36 pm.
Nuvistor is offline  
Old 12th Jun 2018, 9:38 pm   #17
1100 man
Octode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default Re: Twin-panel CRT's

Hi Frank,
The round colour CRT in Shangoo's video seemed to have a separate removable metal clamp band with the mounting lugs on, so the plastic was not having to support any weight.
Good point about multiple reflections though. I wonder what the bonding agent was as it needed to be strong and also very clear? Certainly Shangoo had a real struggle to remove the plastic even though a good part of it had already de-laminated.
Cheers
Nick
1100 man is offline  
Old 12th Jun 2018, 10:26 pm   #18
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
Default Re: Twin-panel CRT's

Safety glass is made the same way, the filling in the sandwich absorbs the shock. My Pye set has safety glass in the cabinet front that had delaminated in a similar way but easy to get a replacement. Widely used in car windscreens but they have obviously fixed the ageing problem.
PJL is offline  
Old 12th Jun 2018, 10:53 pm   #19
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
Default Re: Twin-panel CRT's

Yes, my Bullnose Morris car has it's original 1926 Triplex safety glass which is beginning to resemble that General Electric TV
__________________
Kevin
McMurdo is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 8:27 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.