KPIE172
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CRT "Burn-in"

Thu Aug 02, 2007 5:23 am

Unless I am mistaken the picture below appears to show the FO's and center screens having what I've known as "burn-in"...? As a pilot is it distracting during daylight hours? What is the fix, just replacing? I know LCD's do not have this problem, so why not replace the crt's with newer lcd's of the same dimensions?


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tdscanuck
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RE: CRT "Burn-in"

Thu Aug 02, 2007 6:16 pm

Quoting KPIE172 (Thread starter):
Unless I am mistaken the picture below appears to show the FO's and center screens having what I've known as "burn-in"...?

That's certainly what it looks like.

Quoting KPIE172 (Thread starter):
What is the fix, just replacing?

Yes.

Quoting KPIE172 (Thread starter):
I know LCD's do not have this problem, so why not replace the crt's with newer lcd's of the same dimensions?

Boeing doesn't have any LCD's certified for the 757 flight deck, as far as I know. There are third parties who have STC's to do this though. I doubt it's a cheap modification.

Tom.
 
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Jetlagged
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RE: CRT "Burn-in"

Thu Aug 02, 2007 8:47 pm

When the CRT is operating burn-in would not be so noticeable. Replacement is the only answer.

Quoting Tdscanuck (Reply 1):
Boeing doesn't have any LCD's certified for the 757 flight deck, as far as I know. There are third parties who have STC's to do this though.

The one I've seen involves a complete panel replacement (full glass cockpit), rather than a direct LCD for CRT replacement. I don't suppose it comes cheap, but that is probably offset by reduced maintenance costs long term.

Even a straight LCD for CRT replacement would have to be certified, so with no additional benefit might not be cost effective.

CRT burn-in looks ugly with the CRT off, but when it is on it is nowhere near so obvious. Unless they have already changed the EADI's in the picture you can see both are on and neither looks abnormal. The lower EICAS is usually off in flight, so wouldn't look too good of course.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
EMBQA
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RE: CRT "Burn-in"

Thu Aug 02, 2007 11:22 pm

Quoting KPIE172 (Thread starter):
Unless I am mistaken the picture below appears to show the FO's and center screens having what I've known as "burn-in"...?

That is not 'burn-in'..... he just has the brightness level turned way down
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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Jetlagged
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RE: CRT "Burn-in"

Fri Aug 03, 2007 12:42 am

Quoting EMBQA (Reply 3):
That is not 'burn-in'..... he just has the brightness level turned way down

The F/O EADI is on low, but the EHSI looks like it is off. Being low brightness wouldn't make the display appear negative like that, would it?
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
EMBQA
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RE: CRT "Burn-in"

Fri Aug 03, 2007 12:47 am

Quoting Jetlagged (Reply 4):
Being low brightness wouldn't make the display appear negative like that, would it?

After I took a second look at it.. you might be right.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
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moo
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RE: CRT "Burn-in"

Fri Aug 03, 2007 3:13 am

Quoting KPIE172 (Thread starter):
I know LCD's do not have this problem, so why not replace the crt's with newer lcd's of the same dimensions?

Theres no particular reason why LCDs and TFTs can't have the problem, and indeed we have a few at work that have burn in - it works differently, but it has the same effect.
 
modesto2
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RE: CRT "Burn-in"

Fri Aug 03, 2007 3:56 am

I've seen "burn-in" on the RMU's in the E145's we fly. It's somewhat annoying but not that bad, and I'm certainly not expecting the company to change the displays anytime soon.
 
lincoln
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RE: CRT "Burn-in"

Wed Aug 08, 2007 2:20 pm

Just remember that burn in occurs because the same image is displayed for an extended period of time (and/or at very high brightness settings), thus we can presume that that this is the "normal" display for those monitors and that the burned-in image won't be distracting the majority of the time because that's what's on the screen anyway (or something like that).

Quoting Moo (Reply 6):
Theres no particular reason why LCDs and TFTs can't have the problem, and indeed we have a few at work that have burn in - it works differently, but it has the same effect.

Ditto that! In litterally hundreds of LCD displays I've stared at I've seen burn-in like symptoms on maybe 3. On one of them it just kind of disappered over time...not really sure what happened to the other two.

Lincoln
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777236ER
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RE: CRT "Burn-in"

Wed Aug 08, 2007 7:14 pm

Quoting Moo (Reply 6):

Theres no particular reason why LCDs and TFTs can't have the problem, and indeed we have a few at work that have burn in - it works differently, but it has the same effect.

LCDs can have image persistance, not burn in. It can be cured easily (display a solid block of colour for a while, or rotate through the colour range), whilst burn in can't be cured economically.
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Klaus
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RE: CRT "Burn-in"

Wed Aug 08, 2007 8:33 pm

Quoting Moo (Reply 6):
Theres no particular reason why LCDs and TFTs can't have the problem, and indeed we have a few at work that have burn in - it works differently, but it has the same effect.

CRT burn-in is a local and irreversible degradation of the fluorescent layer. Since LCD don't have such a layer at all and are working completely differently, they can't experience the same effect.

As said above LCDs can show "ghost images" for a while when changing between contrasting images, but those will vanish on their own again.

Degradation with an LCD primarily affects the separate backlight through gradual loss of maximum brightness, but those can usually be replaced at reasonable cost while the CRT would have to be replaced completely, quite possibly with its deflection circuits as well and usually followed by nontrivial re-calibration, especially when colour CRTs are concerned.
 
Goldenshield
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RE: CRT "Burn-in"

Wed Aug 08, 2007 8:52 pm

Quoting Klaus (Reply 10):
CRT burn-in is a local and irreversible degradation of the fluorescent layer. Since LCD don't have such a layer at all and are working completely differently, they can't experience the same effect.

Oh my. Klaus posting outside of the non-an forum, and not discussing Macs? Alright, who are you, and what have you done with Klaus!
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Klaus
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RE: CRT "Burn-in"

Wed Aug 08, 2007 9:20 pm

Quoting Goldenshield (Reply 11):
Oh my. Klaus posting outside of the non-an forum, and not discussing Macs? Alright, who are you, and what have you done with Klaus!

We're getting a bit off-topic, aren't we?  mischievous 

Tech/Ops is by far the most interesting aviation forum for me around here; I just didn't have the time to follow it much in recent months...

But I appreciate the enthusiastic welcome, of course! Big grin
 
NoWorries
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RE: CRT "Burn-in"

Thu Aug 09, 2007 6:50 am

As noted above, the liquid crystals in an LCD are not light emitters, just "valves". Each pixel typically has four segments arranged in a square, two with green coatings, one with a blue, and one with a red. The crystals change their twist (and ability to pass light) when a voltage is applied. Some displays use crystals that are twisted "shut" when unpowered and when a voltage is applied, they twist open. Others are twisted "open" when unpowered and when a voltage is applied, they twist shut. Not sure which type is more prevalent. The degree to which the crystals open or shut depends on the voltage applied (and in this sense an LCD is very much an analog device). If a group of crystals has maximum voltage applied for an extended period, they can fatigue and lose their ability to fully recover. In extreme cases the damage can be permanent.
 
N231YE
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RE: CRT "Burn-in"

Thu Aug 09, 2007 10:00 pm

I am surprised to see the ERJ uses CRTs. The benefits of LCDs outweigh CRTs, lighter, cooler-running, and much less power consumption, and being a younger aircraft, I sure would have thought the LCD would be a better option.

Quoting Goldenshield (Reply 11):
Oh my. Klaus posting outside of the non-an forum, and not discussing Macs? Alright, who are you, and what have you done with Klaus!



Quoting Klaus (Reply 12):

Agreed...Klaus has posted much in Tech/Ops lately. I guess I'll have to start a Leopard vs. Vista debate in Non-Av and keep him busy  wink 
 
Klaus
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RE: CRT "Burn-in"

Sat Aug 11, 2007 1:10 am

Quoting NoWorries (Reply 13):
Each pixel typically has four segments arranged in a square, two with green coatings, one with a blue, and one with a red.

I can't say for sure that such an arrangement didn't exist anywhere, but normally there are only three colour-sub-pixels of equal size. LED-based displays sometimes use more than one LED for a given colour to compensate for colour-specific performance deficits. But I've not seen that in LCDs so far where the colours are realized by semitransparent filters in front of three monochrome LCD shutters. And given that the filters are of comparable quality there isn't a reason for it.

Quoting N231YE (Reply 14):
Klaus has posted much in Tech/Ops lately. I guess I'll have to start a Leopard vs. Vista debate in Non-Av and keep him busy

You'll manage.  cool 
 
NoWorries
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RE: CRT "Burn-in"

Sat Aug 11, 2007 2:40 am

Quoting Klaus (Reply 15):
I can't say for sure that such an arrangement didn't exist anywhere, but normally there are only three colour-sub-pixels of equal size.

Yep, thanks. Halfway through I must've forgot I was writing about displays and thought I was writing about cameras. One common CCD arrangement with lower cost cameras is four cells per pixel (two grreens, one red and one blue).
 
Klaus
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RE: CRT "Burn-in"

Sat Aug 11, 2007 3:51 am

Quoting NoWorries (Reply 16):
Halfway through I must've forgot I was writing about displays and thought I was writing about cameras. One common CCD arrangement with lower cost cameras is four cells per pixel (two grreens, one red and one blue).

Ah, okay. That's quite possible... in a camera the pixel area relates to its susceptibility for noise as well, so it could well be in order to dampen the noise in the colour which the eye reacts the most to.

It is also one reason why "many megapixels" can be a bad criterion to choose a camera by if they are squeezed into the same physical area...

[Edited 2007-08-10 21:01:54]
 
zenarcade
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RE: CRT "Burn-in"

Sat Aug 11, 2007 12:39 pm

Quoting Lincoln (Reply 8):
hus we can presume that that this is the "normal" display for those monitors and that the burned-in image won't be distracting the majority of the time because that's what's on the screen anyway (or something like that).

Well said!

Which aircraft was the first to have LCD panels? 777? 717?
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N231YE
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RE: CRT "Burn-in"

Sun Aug 12, 2007 2:07 am

Quoting Zenarcade (Reply 18):
Which aircraft was the first to have LCD panels? 777? 717?

I believe it was the 777.
 
AJ
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RE: CRT "Burn-in"

Mon Aug 13, 2007 7:59 am

On the 767 (so presumably the 757) the EICAS and EHSI screens are interchangeable so occasionally slightly burned engine gauges are visible sideways on the EHSI. Our company policy is to turn down all EFIS screens whenever conducting the secure checklist to minimise CRT damage. Whilst our 747-400s are getting LCD screens the 767 is not.
 
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HAWK21M
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RE: CRT "Burn-in"

Mon Aug 13, 2007 3:57 pm

Quoting AJ (Reply 20):
On the 767 (so presumably the 757) the EICAS and EHSI screens are interchangeable so occasionally slightly burned engine gauges are visible sideways on the EHSI. Our company policy is to turn down all EFIS screens whenever conducting the secure checklist to minimise CRT damage

True.The B757s EICAS & EHSI crt screens are interchangable.Company SOP is to reduce Brightness when not needed.
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MEL
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