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Why do backlight LEDs burn out and go blue?

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james_s:

--- Quote from: bw2341 on November 08, 2021, 03:53:57 am ---It seems that remote phosphor products use royal blue LEDs which are shorter wavelength than regular blue LEDs. I haven't seen royal blue LEDs myself, but they apparently do look strange compared to regular blue.

--- End quote ---

They look pretty much like ordinary blue to me, I've removed the remote phosphor panels from some old Philips LED bulbs that were intermittent and the exposed blue LEDs are a very bright saturated deep blue. It definitely looks blue rather than violet. It's kind of pedantic to debate anyway, I don't remember where the exact cutoff between blue and UV is defined but it's a continuous spectrum, just deeper and deeper violet that your eyes are less and less sensitive to. All sorts of stuff will fluoresce across much of that span.

gnavigator1007:
We have a similar issue with many of the street light leds around town

magic:

--- Quote from: eti on November 08, 2021, 03:31:28 am ---One would think, would one not, that a thread asking "why", and not "if" the LEDs have lost their white output, would be enough to satisfy people that I've sussed pretty quickly that THE LEDS **HAVE** GONE OFF COLOUR.
[...]

--- End quote ---
Your original post consisted exactly of a single "muh tv has gone blue" picture and a few links to people who happened to have the same symptom and zero mention of any diagnosis performed by you on your TV.

That sort of posts are the staple of Internet geniuses who did their homework by googling for 5 minutes and know exactly what the problem is and only need help with "that one final bit".

The response was totally predictable.

Ranayna:
Uhh, that should go into the pet peeve thread as well :D

Post as much information about the issue you want help with as you can.
People cannot read minds, even here  :-//


* Name the device or software your question is about. If possible the exact version.Software and Hardware versions can differ greatly. With software, many known issues can be fixed with updates.

* Quote any error messages you get. And quote them exactly as you get them. Pro-Tip: In Windows, on many (sadly not all) error messages, hit CRTL-C on the message box to get the contents into the clipboard, ready to paste. On recent Windows 10 (i think 20H1 and higher) hit Windows-Shift-S to start the snipping tool. Or hit ALT-PrintScreen to screenshot your current window.The Error message details, if available, are important

* List what you already have done or researched. If you followed any online guides, link them.If you do not want the helpers to repeat the most basic troubleshooting steps, you have to list what you have done already. It's generally fine if you have not done anything yet, but tell us.


This should be included in *any* post seeking help. I have posted lists similar to this, or have seen them, in many many forums that allow help questions. This is, i my opinion, just basic decency, to not waste the time of the helpers, and your own as well.

I do not know if people are afraid to post such information to protect from potential identification, or if people think that no one knows the device anyway. Or, and i am afraid that this is actually the most likely, if people are just too lazy.[/list]

Zero999:

--- Quote from: james_s on November 08, 2021, 04:30:50 am ---
--- Quote from: bw2341 on November 08, 2021, 03:53:57 am ---It seems that remote phosphor products use royal blue LEDs which are shorter wavelength than regular blue LEDs. I haven't seen royal blue LEDs myself, but they apparently do look strange compared to regular blue.

--- End quote ---

They look pretty much like ordinary blue to me, I've removed the remove phosphor panels from some old Philips LED bulbs that were intermittent and the exposed blue LEDs are a very bright saturated deep blue. It definitely looks blue rather than violet. It's kind of pedantic to debate anyway, I don't remember where the exact cutoff between blue and UV is defined but it's a continuous spectrum, just deeper and deeper violet that your eyes are less and less sensitive to. All sorts of stuff will fluoresce across much of that span.

--- End quote ---
I've seen the term Royal blue used on data sheets. It is indeed a slightly shorter wavelength, than ordinary blue used for illumination, but colour perception is subjective and LEDs differ between manufacturers.

Phosphors are often mixed to produce several different wavelengths to ensure a good colour rendering index. It's possible the green-yellow part of the phosphor has faded more than the red, giving a more purplish/violet colour.

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