how to test lcd led backlight?

[RJARRRPCGP]

Re: how to test lcd led backlight?

replaced by OLED, which is self emissive and addressed dot-matrix style--Ie--No LED/CCFL/Light Source Backlight.....

I hope so, with the fact that plasma is expected to be totally killed.

[tom66]

Re: how to test lcd led backlight?

Ceramic caps are pretty reliable. We buy them from Chinese & Taiwanese suppliers, we've had no major issues. The main problem is cracking of the MLCC. In most cases, this leads to an immediate failure at the factory (I don't think we've had a single field failure due to cracked MLCC, and in the few units we had cracking at the factory it was put down to improper reflow processes.) We don't use polymer or oscon yet, so can't really comment on them. With the new super-integrated COT buck converters we're finding we have no need for poly/oscon and can get by with <100uF ceramic for CPU core pulling 7-8A at 1.1V. So it's just worth it to eliminate reliability concerns.

[budm]

Re: how to test lcd led backlight?

The sad part is that when the Chinese start copying the manufacturing process but do not get it right just like what they are doing these days with lytics caps, I am sure we will have bad caps, faked caps problem from China.

[tom66]

Re: how to test lcd led backlight?

The high voltage generator box that he has will be obsolete soon due to rare montior/TV with CCFL are being produced, but the ESR meter will still be needed in the future.

The company I work for (set top box) has eliminated electrolytics on all of their boards. Only 'lytics we use are those in plug-top power supplies but even some manufacturers are talking about polymer or ceramic replacements. Not yet cost effective but in 5-10 years it could be.

Soon, bad caps will be a thing of the past...

[JeffJ]

Re: how to test lcd led backlight?

Ah--Yes, Forgot about that!! Gawd--In my day, you got caught cheating--That was your lot, finished....

I think this thread should be re-named, The Weird World of Peter Chiu......

We would have been expelled on the spot in my school if you got caught cheating on exams or finals.

[Alastair E]

Re: how to test lcd led backlight?

Ah--Yes, Forgot about that!! Gawd--In my day, you got caught cheating--That was your lot, finished....

I think this thread should be re-named, The Weird World of Peter Chiu......

[JeffJ]

Re: how to test lcd led backlight?

He is way behind the curve as far as the technology advancement is concerned and the real world of electronics. Remember he used cheated sheet to get his EE?
The high voltage generator box that he has will be obsolete soon due to rare montior/TV with CCFL are being produced, but the ESR meter will still be needed in the future.

ESR meter has paid for its self 1000x over for me. Love that thing.

[budm]

Re: how to test lcd led backlight?

This threads not 'Silly'--Its downright Strange to the point of Weird! As I said some pages back--I wish I had some of what Peter is smokin'


Probably after 2020--LED will be deader than doornail, as the pictures on those sets are just terrible, and replaced by OLED, which is self emissive and addressed dot-matrix style--Ie--No LED/CCFL/Light Source Backlight.....

No need for your superduper LED Tester then!

He is way behind the curve as far as the technology advancement is concerned and the real world of electronics. Remember he used cheated sheet to get his EE?
The high voltage generator box that he has will be obsolete soon due to rare montior/TV with CCFL are being produced, but the ESR meter will still be needed in the future.

[budm]

Re: how to test lcd led backlight?

By that time the OLED will more likely to replace backlit/edge lit.

"EX: Samsung LED 55' TV
EX: means...... example.....I make up....maybe we can find some ....regularity and similarity of all the LEDS.." MAKE UP, WTF, get on with the real information instead of wasting time with invalid info, if you know what HB LED is you would be quoting he example of 40mA.

[Alastair E]

Re: how to test lcd led backlight?

This threads not 'Silly'--Its downright Strange to the point of Weird! As I said some pages back--I wish I had some of what Peter is smokin'


Probably after 2020--LED will be deader than doornail, as the pictures on those sets are just terrible, and replaced by OLED, which is self emissive and addressed dot-matrix style--Ie--No LED/CCFL/Light Source Backlight.....

No need for your superduper LED Tester then, It'll be as redundant as a CRT Rejuvenator is now!

[JeffJ]

Re: how to test lcd led backlight?

We've left the rails on this threads topic, fell down the gorge and landed in unrelatedville. Population The above post.

Peter Chiu, please refrain from posting your fragmented dreams and keep this thread on topic. It's getting silly now.

[Peter Chiu]

Re: how to test lcd led backlight?

I have a dream last night....I am tired today, and lots work need to be finished....

.................Dream about this...............

...............A multimillion dollar business …...

Year: 2020 ….........................(Back to future)...................................

LED LCD screen getting bigger and bigger and PC board getting smaller and smaller.

A screen taller than you and only one PCB smaller than a iphone 16 ( image.... take out screen and battery) and screen is flexible.....no need AC cable…....generate electronic form magnetic field surround you........Nobody fix TV anymore …I..I..mean components level....just change it …. super Micro SMD technology...lower consumption of the electricity....... let PCB no more problems.......and unfixable.........

[Dream] When I stand in-front of the 120' LED TV, which customer just called me........... I put out one 007 suitcase ….....and I open it...................................

my lovely------US $3000.00---ALL IN ONE------with built in Tablet mobil WIFI so I can order parts on site ----- with All the new TV update software USB sticks-----with build in LVDS tester and all the cables ..with 1G hz logic Spectrum Analyzer-....-with OLED and QD-LEDs testing capacity --LED LCD Screen Waveform Analyzer lll............. only two band in the entire world........one is LED LCD Screen Waveform Analyzer lll by Peter another one is Super-power LED LCD Screen tester V by BUDM

I SAP the screen with my new improvement ( with no sparks.... [otherwise customer might sue me] ….. slowly but surely ,I know this will light up ….even has fews bad LEDs inside)......after I collect $250 diagnostic fee.... I show costumer.... [Ur kids throw a rock on the screen]........%&#@*....

After, they beats up kids, I order replacement screen...... will come in a long roll package...I collect another $1200 for the parts order with WIFI (Why so cheap? President Hillary Clinton, passed a law, all the replacement parts can't exceed the half value of the TV itself.......good.....

then I head out to next destination...about 10 customers per day...
and I use GPS control 10 more other service truck...just like the good old day.......

…......................................to be continued..............................................................

EX: Samsung LED 55' TV
EX: means...... example.....I make up....maybe we can find some ....regularity and similarity of all the LEDS..

[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""
How about giving the link regarding to this LED spec??? Enough of the Class room already or start another thread named Electronics learning.

[Peter Chiu]

Re: how to test lcd led backlight?

5.OHMS LAW go http://101science.com/Radio.htm study and back here
…...........................................................................................................................................................................................................................................................
I really don't know what they're talkin' about …...make me more confused....

OHMS LAW is R=V/I THAT'S ALL !!!

For Veteran:

R=V/I =ΔV/ΔI
Note: Δ …......."delta" = Δ or δ. The operator is used to represent a difference in a quantity,So we can write ΔV = V1-V2 and ΔI = I1-I2. Summarizing, for any truly ohmic device having resistance R,
Voltmeters and Ammeters
https://www.youtube.com/watch?v=yE3eQ6q39f4

https://www.youtube.com/watch?v=e-ORhEE9VVg

[JeffJ]

Re: how to test lcd led backlight?

I see this all the time in my industry as well (computer IT) We order something say from HP it arrives bad, Some times they just send a new one and tell us to throw the bad part in the trash as its not even worth return shipping labels to them. Its all about the money.

Filling our landfills nicely in the processes as well

[keeney123]

Re: how to test lcd led backlight?

Vf is the kicker here. this is exactly why most of the led controllers shut down or drop off voltage because vf is incorrect, be it open or dead short. with out knowing the exact design of each individual circuit. connecting a random box that applies voltage and amperage will smoke something. If we had this info we shouldn't need a tester because we would have schematics. so...

There is a reason why manufacturers consider these non replaceable parts, because diagnostics are tiedeous and the cost to do so is less then them replacing the unit for warranty. I can tell you this. if you have a tv with bad LED clusters under warranty. You get a refurb and they scrap your sent in unit except the boards possibly.

Yes you are correct here. I guess I am a dreamer as I would expect a manufacturer to design a set so the parts are easily accessible . That way the overall energy(meaning the carbon footprint) going into making a product would be less as the product would last longer and would not be scrapped because of a $2 to $10 part. My experience is that before a product is made engineers sit down and discuss the best way to made the unit in order to save time testing and repairing them. This is how one company I worked for went from a $4 million dollar a year company to $100 million dollar a year company with in a 3 year time. Of course that was back in the early 80's

[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" I sure like to know where he gets this info from.

[JeffJ]

Re: how to test lcd led backlight?

Vf is the kicker here. this is exactly why most of the led controllers shut down or drop off voltage because vf is incorrect, be it open or dead short. with out knowing the exact design of each individual circuit. connecting a random box that applies voltage and amperage will smoke something. If we had this info we shouldn't need a tester because we would have schematics. so...

There is a reason why manufacturers consider these non replaceable parts, because diagnostics are tiedeous and the cost to do so is less then them replacing the unit for warranty. I can tell you this. if you have a tv with bad LED clusters under warranty. You get a refurb and they scrap your sent in unit except the boards possibly.

[keeney123]

Re: how to test lcd led backlight?

When I was a kid my Dad would take the tubes out of the TV and bring them down to the hardware store and plug them into the standardized tester to find out which tube was bad. Once he found out, the hardware store had the replacements and he would buy it and our family could watch TV for another 6 months to a year before he would have to do this again. Of course most tubes would fail because of the cathode heater. Yes there were switches and a look up chart.

[budm]

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.

All he has to do is to get lots of screens with all kind of connectors, with many wires for the LED, then figure out the way to find out which wire is for the Anode for which string, and which wire is for the Cathode for which string, then start testing each string to find out which one does not draw current or light up.
Just think about it, if you have 8 wires, how many combination of testing just to locate the correct pair of wire.
Like I said, you treat the LCD panel like and unknown black box with wires coming out and you need to get the right pair first, once you get that right, powering up is an easy part using current limited variable power supply (only about 2W (200V 10mA) power supply is needed) with AMP meter. Standard connector, good luck with that. The whole point of testing is to find out if one or more LED string has open circuit without removing the panel.
I wonder if Peter ever use tube tester, it comes with many switches and socket adapter and big tube pinout charts of just about all the tubes are made and you have to choose correct switch setting, socket after looking at the tube charts.
To solve the problem is to understand what is/are in that black box (LCD panel) and what it needs to work first then you coming up with the solution and tool to power that black box (LCD panel). So ask yourself what do you need to light up those LEDs in that black box.