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Old 13th Aug 2022, 9:48 am   #1
line sync
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Default Sunlight on TV screens

As been as we are all having lots of sunshine at the moment i thought i would ask this question.
Having got lots of TV sets both colour and mono , some are by windows where the sun shines in.
Someone told me along time ago that prolonged sunshine on a tv screen will damage the phosphors so I cover the screens with cardboard or draw the curtains.
Does anyone know anymore about this ?

Robin
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Old 13th Aug 2022, 10:02 am   #2
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Default Re: Sunlight on TV screens

I have heard of CRT’s in shop windows imploding when in prolonged bright sunlight but not in the home. I don’t know about damage to the phosphor but with CRT's being in short supply I would carry on shielding them when it’s very hot like now.
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Old 13th Aug 2022, 11:07 am   #3
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Default Re: Sunlight on TV screens

Sunlight on the screen, that's a new one, why not? I've seen LCD screens suffer from blemishes due to sunlight, but CRT's?
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Old 13th Aug 2022, 11:17 am   #4
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Default Re: Sunlight on TV screens

Way back I do seem to recollect seeing a slight shadow burnt into the phosphor coating where the sun had over time tracked across the screen, yes, these days best think carefully about these things now they're in short supply.
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Old 13th Aug 2022, 7:13 pm   #5
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Default Re: Sunlight on TV screens

I've heard the same about OLED, which seems somewhat plausible.

On the other hand, not all phosphors behave like this. I think BILL TURNER once planted a magic eye in his garden and checked its brightness yearly and found it to be like new, presumably just by looking at it so maybe not too scientific.
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Old 14th Aug 2022, 9:40 am   #6
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Default Re: Sunlight on TV screens

I was told many years ago that persistant sunlight on a colour crt screen could cause the shadow mask to warp in some models due to heat build up being caused by the screen glass creating a greenhouse effect.
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Old 18th Aug 2022, 1:11 pm   #7
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Default Re: Sunlight on TV screens

Hi

When I worked at DECCA manufacturing Televisions, we used to soak test TVs with a testcard running day and night, eventually, it was noticed that some of the sets had the test card burnt into the screen so we then ran the TVs with maximum brightness but no signal until the screens were reburnt but now the testcard could not be seen, then the sets were I believe sold to members of the staff.

So the screen can be burnt

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Old 18th Aug 2022, 1:28 pm   #8
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Default Re: Sunlight on TV screens

Yes a CRT displaying the same stuff for months / years can suffer raster burn; this was often seen on the information screens in places like stations or airports where the display was largely static.

I doubt if sunlight would cause phosphor degradation - the face glass of a CRT should be largely opaque to ultraviolet light so the only effect I can think of would be heating due to infrared, but I guess nobody ever had a telly that faced an open fire or Woodstove....
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Old 18th Aug 2022, 3:02 pm   #9
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Default Re: Sunlight on TV screens

When I was a teenager as I have mentioned before I worked at D&B Television at Kingston Road South Wimbledon.
There was a wood rack that was constructed along Dexion lines that extended from the rear of the building and along what had been the garden path. Faulty tubes would be stored on the racks awaiting collection by the rebuilder.
I accidently managed to knock the neck off a 14" circular Mazda CRM141. This inrush blew the phosphor from the screen but on closer examination test card C could faintly but plainly be seen in the thin layer of phosphor still adhering to the face plate. I can only think the customer used the TV for musical entertainment as many did listening to the test card music.
A possible explanation is that the bright parts of the card had adhered to the front glass maybe baked by the electron stream over the years. There was no sign of the test card when viewing the tube under normal use. That was way back in 1964! John.
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Old 18th Aug 2022, 10:14 pm   #10
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Default Re: Sunlight on TV screens

CCTV monitors can suffer with permanent captions & clocks being burnt in.

Same with arcade games, often ended up with Game Over burnt in, some later ones had this or captions like Insert Coin flashing to give the phosphors a rest.
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Old 19th Aug 2022, 1:51 am   #11
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Default Re: Sunlight on TV screens

ATMs of a good few years ago used to have the bank logo well and truly burned onto them.
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Old 19th Aug 2022, 6:13 am   #12
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Default Re: Sunlight on TV screens

Years ago I had a Fernseh GmbH monitor (b/w) from the police department.
That set showed for its lifetime the entry of the police department.

This picture was burned in!

Now I am anxious about watching this damned 16/9 television on my old teles.
What a luck, I have many 4/3 ratio recordings.

But all the new stuff is 16/9.

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Old 19th Aug 2022, 4:09 pm   #13
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Default Re: Sunlight on TV screens

I remember all those monitor style Ferguson (TX100?) sets in Ladbrokes and Coral with 'Non Runners' burnt into them!
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Old 19th Aug 2022, 7:29 pm   #14
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Default Re: Sunlight on TV screens

I have been wondering about this too. A few years back I restored a 50's Philips set for a friend. It had a 17" MW43-64 which showed great test results on two different CRT testers.
I did notice that the screen which is normally a relatively bright greenish color, was a bit darker and more grey. This could also be because it was not aluminised.

After the restoration, I was wondering why the brightness and contrast had to be turned all the way up, while it was still showing a dark picture. The attached photo shows the picture on this set. The controls are all turned to max.

I replaced the CRT and the picture was perfect. I wonder what was wrong with the original bottle, since the gun in it tested perfect. It seemed obvious that something was wrong with the phosphor coating. The tv could very well have been stored near a window for decades, but I don't know if that would damage the coating. There were also a safety glass in front of it of course.
I kept the bad CRT just because it really made me wonder what was wrong with it. The image looks as if the gun was weak, but it tested as almost new.

Regards,

Jan
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Old 22nd Aug 2022, 11:01 am   #15
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Default Re: Sunlight on TV screens

That is interesting Jan. We have a 12" Regentone [Plessey] at the museum fitted with a Mazda CRM121B 12" triode. It has exactly the same symptoms as your MW43-64.
The emission reads 100% with a hard getter. I can only think the phosphor may have been contaminated somehow. It is an extremely rare occurrence.

In my own collection I have an Ekco TS88 with a 9" Mazda CRM92A. The phosphor is very course, very unusual for Mazda tubes. It is also quite dark in colour but gives a reasonable but dead looking picture lacking sparkle. Again I would put this down to poisoning of the phosphor, maybe a contaminated or poor quality chemical batch. These are the only two examples I have seen where screen phosphor has failed before the gun.
The first picture shows the 'dirty' screen of the CRM92A. The circular patch is an optical fault in the front plastic screen. The second picture is another Ekco TS88, again a CRM92A with a much lighter coloured phosphor giving a brilliant picture.

The 3rd picture shows the poor screen with many dead grains of phosphor. The 4th picture shows the other CRM92A giving a clean display and a crisp picture. The 5th picture shows the unblemished raster. Not the best of pictures but I hope you get the general effect. Both tubes read 100% emission. Note in the 3rd picture I have reduced the contrast to show the poor screen. John.
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Old 23rd Aug 2022, 12:25 pm   #16
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Default Re: Sunlight on TV screens

This is indeed interesting John. I have never come across a "faded" phosphor coat before. Out of curiosity I had to dig out the MW43-64 and compare it with a known working CRT, here the smaller but otherwise identical MW36-64. Both are non aluminised.
It is seen clearly that the bad 17" CRT has a much darker screen colour, just like the examples you showed.

I wonder if these has been a 100% working CRT's when new, and the phosphor has faded over years making it unusable even long before the gun was worn out.

It must have been related to the chemical mixture somehow as you say. Also because the two examples I show are from the same production year, so it must have been related to a batch.

Really a shame these are unusable, since they are not easy to find anymore.

Your picture with the dead spots on the coating is interesting. This is something I also never saw. I did notice that some have a more course phosphor layer, but never saw "dead particles".

Jan
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Old 26th Aug 2022, 9:02 am   #17
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Default Re: Sunlight on TV screens

The MW43-64 has a grey glass filter. I don't know the MW36-64, it was not used in the UK. The first 14" rectangular Mullard was the very rare MW36-22 that did not have a grey glass filter. The screen looked distinctly white. This was soon replaced by the MW36-24 and the later pentode MW36-44 both with filter glass.

I have an original MW43-64 in a 1954 Ferranti. It gives a brilliant picture and appears to have a lighter screen than your example. I will take a picture of it later. Sun too bright creating reflections this morning!

I feel certain that your 43-64 would have been 100% when it left the Mullard/Philips factory. I suspect faulty/contaminated screen phosphor batch mix and years of slow deterioration. John.
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Old 26th Aug 2022, 10:52 am   #18
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Default Re: Sunlight on TV screens

Just a daft thought, what do the screens look like under UV light? Whenever I have tried this I find the screens all look different colours, from almost white to murky green/orange! It’d be interesting to see these dull screens under UV.

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Old 26th Aug 2022, 11:11 am   #19
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Default Re: Sunlight on TV screens

Just to bring things up to date, we all know plasmas had a habit of doing exactly this but very much more rapidly than CRTs ever did. I've seen two year old ones in domestic use with the BBC News 24 banner burnt in. You could improve matters by feeding in a peak white raster for a good while but it never really went away. I assume the phosphors on those were of a similar composition to CRT phosphors.

Some LCD screens when faulty display a memory effect, often showing the previous screen for days! No idea of the reason.

Worryingly a friend has a 55" LG OLED (one of the early ones) which clearly displays the Sky pause logo in the corner. This is common - not sure how more recent OLEDs behave.

Despite this phenomenon being (hopefully) in the past, laptops and phones still have a 'screen saver' built in!
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Old 26th Aug 2022, 12:52 pm   #20
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Default Re: Sunlight on TV screens

I have a few LCD’s with image retention problems, our old Sony 32” does it if you leave something paused on it, such as Netflix, and the EPG, it does fade off after about 15 minutes, my iPad mini does it too, particularly noticeable when I’ve had a circuit diagram on it for a while, and my Philips 19” LCD monitor in the workshop also does it.

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