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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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6th Oct 2021, 4:01 pm | #21 |
Triode
Join Date: Feb 2020
Location: Derby, Derbyshire, UK.
Posts: 25
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Re: White Spot On TV Screen On Turn Off & What Make
I remember staring into the screen as a child in the early 60s and seeing how long I could still see the spot after turning the set off before it (the spot, not the set!) vanished. It will have been a rental set (Rediffusion?) but no idea what make or model.
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6th Oct 2021, 6:49 pm | #22 |
Nonode
Join Date: Aug 2015
Location: Cambridge, Cambs. UK.
Posts: 2,198
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Re: White Spot On TV Screen On Turn Off & What Make
I recall that our family Pye FV1 (1951) was great at the brilliant switch-off spot. And it seemed to avoid screen burn despite the fact that switch-off happened twice per day then - one after the 5pm children’s programmes and again after the 8pm grown-ups’ programmes.
Interesting that, after years of nothingness after switch-off, our current Samsung QLED shows a passable imitation of frame collapse - enough to worry any CRT TV service technician. Martin
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6th Oct 2021, 8:35 pm | #23 |
Heptode
Join Date: Feb 2007
Location: West London, UK.
Posts: 867
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Re: White Spot On TV Screen On Turn Off & What Make
The comment from FireballX (post 21) remined me that I am sure as a child I would get a strong magnet and have fun putting the magnet next to the screen and moving the switch of spot about while it faded away.
John |
6th Oct 2021, 9:02 pm | #24 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,571
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Re: White Spot On TV Screen On Turn Off & What Make
Oh yes I remember doing that as well!
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5th Dec 2021, 12:24 pm | #25 |
Triode
Join Date: Nov 2021
Location: Leighton Buzzard, Bedfordshire, UK.
Posts: 32
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Re: White Spot On TV Screen On Turn Off & What Make
As a field engineer you came across some odd situations. One call said "Spot on centre of screen".
I was surprised to see the inside of the house was a film set. A large man dressed in outrageous colours (for the time), came over and said "I'm the director, it's about the spot on that TV". The TV was on and I saw no spot. I switched it off and there was no spot, so I asked "What spot?" "EXACTY" he boomed - "there's no spot as it turns off." When I told him it wasn't feasible to make the set do this, he just brushed me away muttering he'd have to fix it in post-production.
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5th Dec 2021, 3:12 pm | #26 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: White Spot On TV Screen On Turn Off & What Make
The switch-off spot was not a problem with the pre-war EMI sets. They did instruct you to turn the brightness control down before switching on but surprisingly they made no suggestion that you should turn it down before switching off!
Peter |
5th Dec 2021, 9:25 pm | #27 |
Heptode
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 989
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Re: White Spot On TV Screen On Turn Off & What Make
There was, at least one set, where the on/off switch was ganged with the brightness control, so eliminating this problem.
Before I go trawling through all my sets, can anyone suggest which models incorporated this? Cheers. SimonT.
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5th Dec 2021, 9:34 pm | #28 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,081
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Re: White Spot On TV Screen On Turn Off & What Make
So, when you switched off, was that at maximum brightness (so that the high EHT current discharged the tube capacitance quickly, before the scanning circuit died), or was it minimum (so that the tube was cut off, and it contrived to stay cut off till the cathode fell below emitting temperature)?
Either scenario is possible... |
5th Dec 2021, 10:39 pm | #29 | |
Heptode
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 989
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Re: White Spot On TV Screen On Turn Off & What Make
Quote:
SimonT.
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6th Dec 2021, 3:16 am | #30 | |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,713
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Re: White Spot On TV Screen On Turn Off & What Make
Quote:
See my "Bulman" anecdote at the end of this post: https://www.vintage-radio.net/forum/...62&postcount=9 I did subsequently find the episode on Youtube, but it later got removed for copyright reasons.
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7th Dec 2021, 5:46 pm | #31 | |
Heptode
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 989
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Re: White Spot On TV Screen On Turn Off & What Make
Quote:
Cheers. SimonT.
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The honesty of imperfection.......... |
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7th Dec 2021, 6:06 pm | #32 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,713
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Re: White Spot On TV Screen On Turn Off & What Make
You could argue that ganging the volume control with the on/off switch is the worst possible choice!
The popular Bush TR82 radio has the on/off ganged with the tone pot, so the volume is the same as the last time you used the set. With a TV on/off ganged with the brightness you may still have to readjust, but there again with mean-level AGC, AC coupling etc conspiring together with picture content, there is no "ideal" brightness setting on a typical vintage TV anyway.
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9th Dec 2021, 7:04 am | #33 |
Octode
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
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Re: White Spot On TV Screen On Turn Off & What Make
I've noticed the Plessey MK1 chassis warming up to display a spot when the HT fuse fails!
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9th Dec 2021, 10:30 am | #34 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,571
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Re: White Spot On TV Screen On Turn Off & What Make
My Ferguson '45' (1958) portable has a switch-off spot but it fades fairly quickly.
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There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
9th Dec 2021, 10:46 am | #35 |
Octode
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 1,572
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Re: White Spot On TV Screen On Turn Off & What Make
And a switch off spot on my Ferguson 991T 1954.
Adrian |