Re: how to test lcd led backlight?
? Auto-recovery LED screen ? Resettable Fuse ? Auto-bypass LED?
ST has LBP01 part can bypass any defected LEDs
Benefits
■ Keep LED strings on in case of LED open mode failure
■ Reduced maintenance cost
■ Increase lifetime of the lighting system
https://cdn.badcaps-static.com/pdfs/...34696944c0.pdf
But, new LED TV used 2000 LEDs to make more brighter LED screen. I predict ( Auto-bypass LEDs will be use to build Auto recovery LED screen) in the future !
(I mean, LED will build in bypass circuit in the chip which just two more diodes. )
Tips: So next time don't put a cooper wire cross the defect LED put a diode.This allows the right amount current to flow through the other LEDs.
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Re: how to test lcd led backlight?
Yes that is where standards would work.Leave a comment:
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Re: how to test lcd led backlight?
If you want to use external constant current power source to drive the LED string then the strings are no longer connected to the LED driver board) so there is need to have any power to the TV at all since you are just testing LEDs.
The harder part is to figure out how the strings are connected together and which wire is the Anode and which wire is the Cathode if the panel is not open up to see the LED string, or you can trace the connector on the driver board to see how it is done.Leave a comment:
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Re: how to test lcd led backlight?
Bud M don't laugh at me, but I was hoping to unplug all the LED strings and plug them into a separate power source that would eliminate any feed back circuit from turning the the LED driver chip off.Leave a comment:
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Re: how to test lcd led backlight?
It would be nice if these led strings had standards for each size of screen then one could build a test circuit just to plug in and see if the individual strings worked or not, but that would be to easy.Leave a comment:
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Re: how to test lcd led backlight?
LED's are wired like christmas-tree lights....
One dead--all out.
You just have to test each one in turn. No schematics, just a meter.....Leave a comment:
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Re: how to test lcd led backlight?
That will be correct if all the LED int he string are good, but if one goes open circuit then nothing will happen, but you need to know how many LEDs are in the string to determine what the power supply voltage needs to be, some string you will need more than 100VDC, Vf of each LED is between 3~3.6V.Last edited by budm; 03-27-2015, 12:36 PM.Leave a comment:
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Re: how to test lcd led backlight?
his would be a constant current source would be the voltage regulator.
What do you think?Leave a comment:
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Re: how to test lcd led backlight?
Yes, something like an adjustable voltage source with constant currentLeave a comment:
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Re: how to test lcd led backlight?
OK, are you asking how to test individual LED mounted on the circuit board that form LED string?
You can use 3V battery with 100 Ohms resistor to limit the current for testing individual LED.
Or you already verify that the LED driver circuits are OK but the LED still does not light up?
Test LED string current draw using DCA.
https://www.badcaps.net/forum/showpo...4&postcount=95
Or used indicator:
https://www.badcaps.net/forum/showpo...&postcount=107Last edited by budm; 03-27-2015, 11:55 AM.Leave a comment:
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Re: how to test lcd led backlight?
Jump with a low ohm resitor between ps-on and 5v stby, and 5vstby and bl-on (inverter on off)Leave a comment:
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how to test lcd led backlight?
please post test methods you use
thanks!
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I have a TCL 43S435 with no backlights. I contacted ShopJimmy and they said power supply. I got replacement power supply, but still doesnt work. I have confirmed that there is an image with flashlight test. I have also verified that the led strips work when I probe them with LED tester. Any ideas would be helpful. I am also geting a double blink on the status led when trying to turn it on......Nothing on the power supply looks suspect, and caps look ok. Where should I start to test......Thanks!...
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Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
Upon bringing it home and plugging it up, it showed a standby light.
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The screen seems to blackout and stay black, but with a flashlight I can see the display.
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Hello all,
Am trying to figure out this backlight issue with this A1990 Macbook Pro.
Tests performed:
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Backlight IC is receiving the correct support voltages.
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Hi
I have image but no backlight. Fuse is blown. I think the display is faulty or cable lvds.. but not shorted last 3 pins in connector to GND
.. Can I test the screen backlight only unplugged from motherboard with 32v at those pins? (Expecting to see a backlight only)?
Leave a comment: