how to test lcd led backlight?

[keeney123]

Re: how to test lcd led backlight?

Peter Chiu the only way one could build what you are trying to build is to know how each LED string on all TV's have been connected then a program could be written to start out with the lowest voltage lowest current configuration and send a signal out and look for feed back current. The program would have to step through each possible connection until it found the right connection. Of course if you had an open circuit it would never find a connection. One still would have to take the TV apart to test the strings. The only way around taking it apart is if the manufacturer brought the LED connectors to the outside of the TV were one could disconnect the LED string and connect the tester. All of this testing could be done if you had standardization of the LED connectors. This would be up to the manufacturers to get together and create these standards. If they will not do this then the only way is to do it like BudM is doing. It would be impractical to try and find out of all the ways the LED strings were hook up in TV,s. If you want to try to do that I would contact all the manufacturers who make led strings for TV and find out all the various ways they have made them. Of course you are going to get into proprietary patents of the individual manufacturers. So then you would need to go to all the manufacturers of TV's and tell them what you are trying to do. If they agree to give you that information they will most likely ask for a percentage of the profit.

[budm]

Re: how to test lcd led backlight?

"That is an example....but one CCFL not work... some TV do detect them and go into protection. Why their know ? CURRENT"
Well if you read the 2-second to black thread you will know that, beside I have never see inverter circuit without the error detection circuit to protect itself if the lamp is not connected, or if the lamp is connected and fired up but does not stay conducting, or too much current is being drawn. Your CCFL tester does not have that function to tell if the lamp is good or bad that is why I pointed out about your BLUE BOX CCFL tester that you have.

[Peter Chiu]

Re: how to test lcd led backlight?

That is an example....but one CCFL not work... some TV do detect them and go into protection. Why their know ? CURRENT

I will talk to u ,tomorrow. I gonna go .

[budm]

Re: how to test lcd led backlight?

EX: Samsung LED 55' TV , the LEDs are 7983340.... 33 means 3.3v 40 ..means 40ma and we know from 2015-2018 they use this kind of LEDs /by total current ....we will know exactly how many they used"
So lets say that they use 10 of them in series, what will the total current draw will be and what is the total Vf will be?

[budm]

Re: how to test lcd led backlight?

"EX: Samsung LED 55' TV , the LEDs are 7983340.... 33 means 3.3v 40 ..means 40ma and we know from 2015-2018 they use this kind of LEDs /by total current" Can you show me the spec sheet of this 7983340? 40mA for HB LED?
Look at the typical current draw:
https://www.badcaps.net/forum/showpo...4&postcount=95

[budm]

Re: how to test lcd led backlight?

"but look back to all that CCFL do you still need to open to see what kind of CCFL inside 80 % we know is U shape or straight" once we verify that the inerter board is OK, you still have to open up the panel to inspect the lamp for bad wiring, bad lamp sockets, worn out lamps, etc. Using CCFL tester will not tell you if you have bad wiring at the end of the lamp because the lamp will still light up (high voltage can easily jump the bad connection to light up the lamp) and the main thing about CCFL tester is that it does not have error detection circuit to detect if the lamp is drawing enough current or too much current, or the lamp is actually connected.
Bad lamps:
http://s807.photobucket.com/user/bud...?sort=3&page=1
Beside, the CCFL are connected in parallel separated by ballast caps.

[Peter Chiu]

Re: how to test lcd led backlight?

This confuse me too, this part still under development ... we can now only know the total current no problem, still needs the blueprint from panel manufacturers ... look back to all that CCFL do you still need to open to see what kind of CCFL inside 80 % we know is U shape or straight and how many CCFLs it is ...by open 100 LED screens we can concussion come similarity.......EX: Samsung LED 55' TV , the LEDs are 7983340.... 33 means 3.3v 40 ..means 40ma and we know from 2015-2018 they use this kind of LEDs /by total current ....we will know exactly how many they used
By the way that's my goal to complete...when I finish the prototype I will let everybady know for sure....

[JeffJ]

Re: how to test lcd led backlight?

Peter, an EEprom programmer that can read a chip id, is different then connecting a string of leds. leds would be considered a stupid device they do not identify them selves and they cannot talk back. I can see Budms issues he raises. There really is no way to identify parallel or series wiring with how many leds. And since these are so sensitive, an assumption could cause more damage.

Lets say one manufacturer sells a diode, i could engineer 1001 ways to use that diode that could never be identified blindly by plugging in a box. And this is exactly what we're faced with.

[Peter Chiu]

Re: how to test lcd led backlight?

look EEprom writer from EEV .... he did open one and you can see the design of it .....kinda of Buffer or Darlington transistor or mosfet for switch on and off ...... Ok is like this......I can put any 8 pins Dip EEprom and they will recognize the manufacture and IC no..... I know they read the index or ID first .... but they know you put up side down and not going to burn anyway....some of them has in circuit programming function...

They use microcontroller to store information and each different pin or the timing....roughly about 3000-10,000 each eeproms..ICs....legs pinout. and they can test most TTLs and COMSs too.....

[budm]

Re: how to test lcd led backlight?

LED panel details spec sheet is kinda hard to fine .....but only few guys make it actually

LG SAMSUNG-----koren
AOL-----Taiwan
Apex ---China
Panasonic sanyo sony-Japan
Believe or not that's all, because they low down the cost , nobody else will compete with them.
Form news what I hear Sanyo not happy with samsung take most 120' LED TV market... try untied with China flight it back the 120' LED TV for about $ 2000-$3000.....
In the future, by sorting the panel information will be just few kind only, because everybody try to cut conner........

How is that going to help you finding out how those LED strings inside are connected together, even if you have OLY ONE manufacture, they will have many ways of hooking up the LEDs inside for Edge lit, backlit with local dimming, the size of the screen, etc.

[Peter Chiu]

Re: how to test lcd led backlight?

LED panel details spec sheet is kinda hard to fine .....but only few guys make it actually

LG SAMSUNG-----korea
AOL-----Taiwan
Apex -lots of them ,I don't even know the name --China
Panasonic sanyo sony-Japan

Believe or not that's all, because they low down the price , nobody else will compete with them.

Form news what I hear Sanyo not happy with samsung take most 110' LED TV market... try untied with China flight it back the 120' LED TV for about $ 2000-$3000.....

In the future, by sorting the panel information will be just few kind only, because everybody try to cut conner.......or OEM ...like sony did,,,,,.

.........The hardest part is to figure out the polarity of the wires coming out from the panel......
I think you did teach us use bridge to do it.....then will become non-polarity...

[budm]

Re: how to test lcd led backlight?

cant you just use a regulated psu with an ammeter inline to test the strings for open or short sections?

Yes, just need power supply with low current, 10DCmA will be more than enough and Variable power supply that can go from around 24 to ~200VDC.
The hardest part is to figure out the polarity of the wires coming out from the panel, unless the connectors are labeled with A/K, or +/-, d+/d- then you can spend lots of time figuring out what those 4 wires or 8 wires are, tracing the connection at the circuit board will help when work with unknown. I usually looking at how the board to see how it functions first.
I am sure someone or some tester can do that and find the correct adapter in 10 minutes.

[stj]

Re: how to test lcd led backlight?

cant you just use a regulated psu with an ammeter inline to test the strings for open or short sections?

[budm]

Re: how to test lcd led backlight?

The questions are, without opening the screen how would you know:
1) How many LED strings are inside the TV
2) How many LEDS are in each string, some LED may have two or more LEDs in one body.
3) How the LED strings are connected together, series or parallel, or series-parallel combination.
So unless you have LCD panel details spec sheet you will not know how they are connected, seeing only one pair of wire is easy to figure out, but see 4 pair of wires or more coming out of the panel is another story.
Have some one build a bunch of black boxes with many combination of LEDs connected with a buch of wires coming out and give them to you without giving you the clue as to what are inside boxes and have you figure them out using your test box to identify how many LEDs are inside and how they are connected.
I am sure your professor did you give the student in the lab the black boxes with wires coming out and ask them find out what is in the box using the test equipment to find out what is inside the box.
The connector interface alone will be a big problem since there is no standard for the connector for the LED driver board.
As far as knowing the current handling of the LED, at this point there is no tools that I know of that can figure out the current handling of the LED without getting the spec sheet form the LED manufacturers.

[keeney123]

Re: how to test lcd led backlight?

Yes, I know. I will work on my power supply for testing LED and will post the result after I am done.

Yes, this is what is needed as having it in circuit involves feed back loops. So then if you know the LEDs are good one can then just concentrate on the driver circuit. Thanks BudM for doing this as I think it will make a lot of people's life's easier.

[Peter Chiu]

Re: how to test lcd led backlight?

$ 40.00 is the cost of manufacturing of the products in mass quantities..... not count the R & D and software development. ...to put it another way......is your cast to built each one.

Ex: Like $ 300.00 EEprom writer will cast about $ 40 hardware but firmware needs to update all the time....

First I needs to built a prototype and numerous times to modifier them and find all the adapter for each TV. (each adapter sold separately). patent pending....Dealer....on and on.....I estimate will 10 time more market than ESR cap tester or (if you that old) CRT- rejuvenator..

[Peter Chiu]

Re: how to test lcd led backlight?

Sorry ! what I mean is not open the LEDs screen. The tester is use to diagnose the problem before you open the screen which may cause (like tab ) more problems.

The screen size getting bigger and bigger, I would not open 85" TV unless I'm 100% sure that is the problem. that's what the LEDs screen tester for...

Let's say another word
not open the screen....by use the tester I will know this ...

1: LED's LCD screen is good or not?
2: How many LEDs are inside the screen ? How much is the current they used to drive screen.
3: Which group LEDs is bad ?
4: The problem is LED driver or screen. I need 100% sure.
5: All the test needs to be done ....less than 10 min
6: We can't cut any wire , If TV get fire, we might get sue .
7: Each in home diagnostic testing ( In home service call ) is around $180 to $320 depend on the size of the TV. Pay for itself in fist visit.
8: The symptom of screen broken always misdiagnosis is failed power supply. New LED TV the LCD screen failed ,broken screen,water damage ,screen manufacturer defect, look good but will cause wrong diagnostic and waste a lots company resource. This tester will mend this problem.

With more and more big size LED TV in Walmart ......the tester is the future ...and.... The tester is made in USA....

[budm]

Re: how to test lcd led backlight?

"Will answer the common questions about { Is my screen bad or the LED power driver bad? }! ......cast you about $40......" $40 to find out if the driver is bad?
I think we did pretty well on how to find out if the drivers are good or bad:
https://www.badcaps.net/forum/showth...648#post550648
https://www.badcaps.net/forum/showth...led#post546324
https://www.badcaps.net/forum/showth...led#post537873
https://www.badcaps.net/forum/showth...bad+led&page=2
https://www.badcaps.net/forum/showth...led#post546755

[Peter Chiu]

Re: how to test lcd led backlight?

Alastair E:......not just Testing the LED strips....


Unveil…..........The first............The best tools for TV repairman..............



1: Test all sizes of LED screens (7” to 120” screens) are.... good or not?
2: How many LEDs are inside the screen ?
3: which group LEDs is bad ?
4: Is the LED driver work or not ?

Will answer the common questions about { Is my screen bad or the LED power driver bad? }! ......cast you about $40......

Would you believe.. ... A guy ( don't even know Vf =0.7V ) will design a good tester. Even I don't thing so......so I need to study, again......again......

https://www.youtube.com/watch?v=D_P-v1BVQn8 .....but I ain't gay..

Parts on order......waiting for parts.......please be patient..........To be c.....…...

[Peter Chiu]

Re: how to test lcd led backlight?

….......Keep on........CPT 4: Resistance

<<<<<<<my equation R=1/(1/R1+1/R2+1/R3.......)>>>>>>>>

If R1=R2=R3......are same value (150 Ohm) than will be more easy.............

75 ohm =150/2...... (two resisters 150 ohm)
50 ohm =150/3........ (3 resisters 150 ohm)
37.5 ohm =150/4....... (4 resisters 150 ohm)

IF same value of two resistors put parallel together will be half the one's value.

I will prove to you
but first we change >>>>> R1=a <<<<<<<for easy look

R=1/(1/a+1/a)=1/(2/a)=a/2=means half the a=R1's value=75 ohm

ex:Pick up two 100k resisters parallel together =50k (right-away half the 100k value….)

....................beginners .............................また明日ね。

For Veterans:
Electrical resistivity and conductivity
https://www.youtube.com/watch?v=4rsswT_Rv1M
Intro to Electrical Resistance, Resistors, and Resistivity | Doc Physics
https://www.youtube.com/watch?v=XoI6QmQeAXo
Resistivity
https://www.youtube.com/watch?v=FPZiMVna1ls
Resistivity, Resistance, and Conductivity
https://www.youtube.com/watch?v=bK-9U-9eW_Y

Friendly remind;
You gonna learn all that today, because this is lesson 1

your rewards:
https://www.youtube.com/watch?v=i8rMpN4o-b0

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