LED backlight problems in TVs and computers.
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- čas přidán 2. 08. 2024
- When I first heard they were going to replace the Cold Cathode Fluorescent Lamps used in LCD TVs with LEDs I thought it would be a great idea. Now that I'm seeing many LED TVs coming in here with burnt out LEDs I'm not so sure it was such a great idea. I'm guessing part of the early failure I'm seeing with LEDs is because they are driving them too hard. Because I was seeing more TVs made by LG than any other model coming in here with bad LEDs I did a voltage and current test to see if I could figure out why. What I discovered is that some of their smaller LCD LED TVs have an excessive amount of current and voltage going to their LEDs for the first 10 seconds that the TV comes on. In this video I talk about some of the problems I've seen, and I hope others may contribute additional information on this topic. After making this video I learned that Union Electronics sells LED replacement strips for LG TVs at a good price.
The most informative LED TV repair video yet... Thanks for actually explaining how some of these units go bad. I have an LG 50LN5600 model and change all 3 boards due to bad LEDs. I was told by many technicians that my T CON board was bad. I was getting the LG logo flash with the blinking red light. Then the TV would go black. Neither board was bad... LED was bad.
Great video. All of us from MikesTVTips appreciate it. I also am seeing more and more of these led failures. I built my own led tester using two junk remotes. I'm basically using them for the battery holder. One remote takes two AAA batteries (3v), and one remote that takes four AAA batteries (6v). I cut the top half of the remotes off and attached wires to the + and - terminals. That way I can test different kinds of leds individually. Once I locate the bad led, I will desolder it and cut a good replacement out and stick it over the one that I removed and hook up the jumper wires. I'm with you! The manufacturers do not care how long this junk lasts!
great videos with good mix of practical hands-on troubleshooting along with the theory and thought process behind it. keep up the good work.
Good vid, you are the only one on CZcams I've found so far that mentioned LEDs can be working but drawing too much power indicating imminent failure. My TV has a flicker. Took the easy way out and replaced the PS board. Didn't work so I opened the TV up to look at the LEDs, all lit. Replaced the Main board next, still no joy. After consulting a local repair shop was informed that my LEDs are possibly drawing too much voltage/current and as a result the Main board is cycling. I was also told NOT to replace ALL the strips as the TV would require professional calibration. A few strips okay. Now I'm trying to hunt down replacement strips.
I've never heard anyone say not to replace all of the strips due to some kid of calibration. It's been my experiences that only replacing the bad LED strips is likely to be a problem, since the ones you don't replace aren now so old they are likely to fail soon.
I had the same trouble with my RCA . I replaced only 4 strips on a 55 inch that needed 12 strips and it only played a little over 2 month and went out again. You have to replace them all or just get another tv. Before they come out with these stupid led tvs I had a TV that lasted for 6 years and was still working I got rid of it. A led tv sure is not going to last 6 years. Hope when the O Led tvs go down in price it will be better than a led or maybe as good as the older tvs. Good video thank you for posting.
Great Video, I wish I found this 2 weeks ago when repairing my samsung 32", it would have saved me much heartache. Great advice on the LEDs being so impossible to find. I also ordered a 5050 on eBay and it didn't fit at all as you mentioned.
An excellent and valuable informative video. Anyone who does repairs for other people should understand the challenges they face when dealing with back light problems. Some fluorescent back lights require the skills of a brain surgeon to replace, especially those devices that have no replacement procedures available from any common source.
Cross referencing part numbers is a challenge in itself too, especially on Ebay where there's lots of one size fits all (wrong) parts for sale.
Another excellent video. Thanks. FYI:
While I no longer repair TVs as a living, I have an LG 32LN5300 that has an the LED string opening up intermittently. At first I thought it was the power supply because because there was very little voltage across the string. But after finding the datasheet for the LED driver (MPA3202 IC), I realized the power supply was shutting down because the LED string was opening up. The TV has since started behaving so I haven't pursued the repair any further. Thanks for the tip about damaging the screen. What I found is the driver is a constant current source that only puts out a current level of 372mA. If the LED string is open, the drive voltage will go very high briefly and then shutdown. It really pays to use an oscilloscope when measuring the LED drive. To control the brightness, the TV turns the drive on an off at a 120Hz rate. At the default brightness, the on duty cycle is 34.7% yielding an average current of 129mA. Like you observed, for the first few seconds after turn on, the duty cycle is 100% and then the main chassis reduces the PWM duty cycle to 35% over several seconds. I suspect they do that to get the LEDs up to temperature quickly so the color rendering is correct. Even at fully brightness the duty cycle is less than 40 to 50%. I suspect they strobe the display so there is no light when the LCD is switching states to
prevent artifacts.
In terms of LEDs going bad, very few of the products I work on ever have an LED to bad. But the ones that do, it has almost always been a case where they are over driving the LED by 50% or more over its rated value. I bet the LEDS in these TVs are going bad because they are exceeding the LED specs for current or failing to take the derating effects of temperature into account.
+StevesProjects Thanksj for the info.
This is a great video! I have changed many LED bulbs on TV sets in my shop. If you don't care I have a few tips for your video viewers and do-it-yourself'ers. Use good LEDs! I found the LG LEDs for backlighting on ebay. The most common rating on the bulbs used for backlighting is 3.6V at 1 watt. I bought 100 for $25 and they work in most sets. I have noticed the TV manufacturers do tend to overdrive the voltage a little get more brightness out of the bulbs. They can handle a little more voltage as long as the current is limited internally by the TV power supply. The LG bulbs seem tough and I have not had one blow yet. Do not install these with a normal soldering iron. They will not handle the heat long. You have to use a hot air station set to 200 C and low temp soldering paste like 247 solder paste that melts at 137 C (278 F) Only takes a few seconds of heat to solder them on and you won't damage the bulb at that temperature. I use clear silicone to anchor the lens corners back over the LED. It is important that the lens is exactly centered like original or you will get funny circle patterns behind the LCD! Good luck.
Thanks for the information. Hopefully the viewers will read the comments in the information section for tips like yours.
Thanks for a great video and I've been watching around 30 past few days trying to fix a tv.
First, I am glad that nowadays LED TVs are so easy to fix, unlike old cathode screen TVs (which I hate fixing). I have the plasma and I would not let it go until I must... but since I am into electronics whole my life - around 28 years and counting - my friends rely on me to help them fix broken electronic devices.
Now I am trying to fix a Panasonic 32" for my friend. I found one led has died and I did a math measuring healthy strip. I found that strip is sucking 200 mA. Therefore a resistor of around 16 Ohm will/should work on the place of LED. I've put a resistor of 2 W 22 Ohm (I did not have 16 Ohm) there and it worked!
I let it run for full 2 days at my place and then I brought the TV back to the friend and - it died within an hour. I dismantle the damn thing again and I found another broken LED. I've put a resistor there and... it would not turn on. It even does not have flash when plugged in into 230 V (I am in Europe).
If you want to ask "why resistor"? The answer is - I do not have a LED that will run on 3.6 V sucking around 200 mA. I assumed it is LED of 1 W and I ordered 50 of them from the Ebay for $3.80, but until they get here... it will take a month probably.
Anyway, I am now thinking to use high power led strips made for car daylight (since the damn thing would not bring light now) and make it work with fixed light level :) until those LED's came here. To add, if needed, another rectifier for 12 V to power those lights. Or to make a combo of them and existing working LED's.
I am wondering - and sorry for such long message - have you fixed the light controller sometimes? Since there is no flash on turning on, I am thinking that the light controller is bad also. I know I can order 2 replacement strips ($15 each + $20 postage and this is getting close to a value of a used TV) and the controller (in this TV it is a circuit that includes rectifier), but the owner is, well, one poor old man and I am trying to help.
Again, thanks for vid, you made me laugh few times loud ("some genius came up with the idea...":)).
I don't remember if I ever had to replace the LED driver, but I replaced a few of the CCFL drivers on the first versions of LCD TVs.
a great tip to prolong the lifetime of your led backlight: in the settings/menu area, take the backlight and bring it down from 100% to about 70-80% heck even 85% and it will last for a few more years! i recommend to do this the day it comes home from the store, or asap. getting to the led backlight is a pain in the butt. yea, it wont be as bright, however you wont be running at max current, hence prolonging the mtbf. besides, after about an hour watching it you wont miss the brightness.
Great Video! thanks! 73!
+su pyrow Yep. I took my Sanyo LED/LCD down to about 70% or so. It's a little over 3 years old and doing great. After checking, it is at 65% and still has a beautiful picture.
+sporadic -Z Planned Obsolescence...
+Robert Calk Jr. It is not obsolete if you know how to overcome it.
+su pyrow For people like us. But they know the average person will just chunk it and buy a new one.
+sporadic -Z It is. And they are real good at fixing the breakdown expectancy also. It's also getting harder to get schematics, and a lot of service manuals that I've been getting don't even have full schematics.
THANK YOU FOR YOUR VIDEO AND ALL THE INFORMATION.
Very instructive commentary. May stick to ccfl replacement with ccfl instead of led.
Seems to be another case of putting a new product on the market,before it's been fully tested and of course they know a lot of people will just buy another set rather than go through trying to get it repaired. Hopefully someone will come up with a way to fool the feedback circuits. Thank you for another well done video.
With the current price of reasonable labor, good luck on finding someone who will spend the time repairing backlights on an older (2 years+) TV's or monitors.
great job as always, nice info, thanks
Thanks Tampatec.
If you talking about my lights they are LEDs which put out 60 watts of light, but their combined power consumption is less than 100 watts.
Call me when you get the chance.....I have some updates for you to share on troubleshooting and repairing LED strips. Wayne from AffordableMobileTVRepair.com
+Grants Pass TV Repair lol, no reply after that. I guess he moved on to the next youtuber with good lighting in their videos. it would be funny if he lived in Vegas city of lights. ( I also switched to Led)
Yes, another so called expert, shooting off his mouth. He doesn't even listen to the facts before acting like a jerk and jumping all over Dave. As far as I am concerned, he owns Dave an apology.
Nice video, I have learned a lot from you since I found your channel, so thanks. Now perhaps I can share something with you, LEDs are current devices so it best not to think in terms of voltage, as you noted Kirchhoff's Voltage Law holds true and the sum of the voltage drop of the LEDs in series will equal the source. It is better to think it term of current, as current through a series circuit is constant. This is why we use a constant current source to feed a string of LEDs, set it for you desired current and connected it to your LEDS, it does not matter if you have 1 or 100 LEDs it will just keep supply the current you set independent of source voltage or load (i.e. number of LEDs). Do a Google on constant current circuits, you can you discrete transistors or even a LM317 regulator, they are surprisingly simple circuits with a ton of applications and fun to play with. Keep up the good work and keep the videos coming.!!!!
+Michael Katt I appreciate your suggestion about using a current regulator. That's an approach I hadn't thought about. Thanks.
Well let's say that straight, it's the "programmed failure" desing :) LEDs circuit is designed to give too much current or voltage so LEDs get burned at some time, putting there resistor was a good idea but designer was smart enough to block it with loopback circuit shutting down TV ;) That's where electronics desing is today.
Awesome info, thx.
I recently learned that Union Electronics has the replacement LED strips for LG TVs at a reasonable price.
Nice info. Thanks!
Thank you, great job!!
Yep covers all the points. Repaired LG 32 inch. Very risky on the fragility of the LED display and it's ribbon cables. Totally agree on absolute poor(deliberate?) Design. CZcams recommends turning down your back light settings. Had an issue of Back light going down on Samsung over parts of screen and it was intermittent. I turned down the settings to 50% on the backlight and it has stabilised. On some mode settings cannot adjust settings. I see loads of these sets going to the tip and at 6/700 UK £ a pop it's a disgusting waste. I have a 22 inch flat screen computer monitor that has been going for 10 years. It uses discharge tubes. Thanks for very informative video.
Good video. As a newby here I notice that some video are quite yellow, so you might want to look into different lighting for those.
I sure enjoy your videos. This can be a very frustrating business to be in.
great vid,but like you finding replacments is harder than you think.iv found that hoarding them from broken screens,but still having problems with edge lit and oled and rgb smart 3D leds match
I've seen LG's where the led caught fire and it burned a decent amount of deflector paper with it ! Dangerous for sure.
I think you're correct about the LED'S being run to hard.I know if an LED is run properly they will last for many years.I still have a LED flash light i made myself that is over 10yrs old with the original battery.I know people who read this will say a battery that lasts 10yrs+ no way.but its true here is the type of battery:
Tadiran TL-5242/W 3.6v Lithium Battery.I found a few of them is this warehouse i was doing repairs in long ago.
I noticed that the leds that burn out have a gap between the chassis and the aluminum substrate the leds are mounted on so I do and recommend using a thin clear mounting tape to secure the strips. I even had done a tv requested to use thermal paste and tape. The things I noticed lately is the strips are bent and assembled poorly at the factory with strip snaps falling inside.
In order to regulate current with a discrete diagnostic system is to incorporate a current regulator at the input voltage to each strip. Using just a resistor will not work. I have had luck dropping in rush with a small voltage compatible incandescent light bulb.
you make good video's very educational
Good video thank you.
update: LG and vizio now have firmware updates to correct the voltage issue, maybe they watched your video. update with usb drive or connect TV to internet to update TV and go into tv settings to select update.
I don't know which LG models the firmware upgrade works on, but it wasn't available for the model I had. Please let me know if you have any luck with this on other LG models.
The firmware wont change the driver current or voltage, might possibly mean that the backlight is driven lower in the menu from factory but wont correct it burning out at max still.
Is it possible to use a different led strip ? I cant find the exact one for my tv
Yes it's possible to use a different LED strip as long as the replacement uses the same voltage and current as the original, and is long enough to evenly illuminate the display.
Makes me appreciate my 10 year old Sam DLP TV. Picture gone dark? 1 screw, pull out lamp, insert new one. $85 every 4 years.
Found an lg 50 inch that only had one led burned out ! Nice find for me !!
Sadly I don't think you can count on your LG TV to last. If one LED was bad the others will soon follow.
This is a big issue here in the UK. when the sets start the leds light very brightly and then dim. We have been repairing loads of these. got a few tips for.you sometime.
Bad luck there buddy I have never cracked one yet done over 90 just got to handle the screen carefully. Also they add less Leds to keep costs low and push the ones still there harder to maintain the same light output of course the little smd led gets very hot and dye of the led cracks either shorting the whiskers or making the fail open causing the whole backlight to fail. All of them are shit.
What about grabbing the LED strips from autozone and wiring them in parallel as replacement backlighting and giving them it's own dedicated 12v power source AKA transformer rectifier?
That sounds like as possibility so long as you can disable the feedback circuits that need to sense a particular load in order for the TV to stay on. The other important thing is that your backlights from autozone must not have any kind of flicker rate.
Also with Lg's they use higher current at lower voltage at start then when the pwm kicks in it lowers current and upps the voltage not a design flaw its getting the minimum load and compares it to make sure the leds are good.
were can I source these leds strips ?
The most common source to me is Ebay, but these are usually used items which may or may not last long. Maybe OK for personal use but I wouldn't guarantee it on someone elses devices.
good video please make more thank you
I think this is more an issue driving LEDs than it is the LEDs themselves. They're very sensitive, and heat plays a huge part in the lifespan of the LEDs.
Instead of a stacking repair (one board on the old one), could you cut a section out of the old one and put the replacement board section in the gap. That way, the leds will be at the same height and it should be a fairly quick repair. Make it a very loose fit to quickly replace dead leds.
As much as I hate the fluorescent lamp backlight, mainly for it's lack of brightness and lower contrast ratio, with LED, I always have that fear that if one burns out, the whole strip could go out with it.
On the newer LG LED flat panel tv's, you will notice a connector between the left and right strands. on either side are 2 bare copper test points. Simply bypass this connector by soldering these test points together with 16 gauge wire. positive to positive, negative to negative. These connectors are known to fail...
I have not encountered this yet but thanks for the tip.
good video
Paul Spiller
I work on small engines and am amazed at how many people just dispose of stuff because its actually cheaper to buy a new one than take it to a repair place. Indeed I have talked to several repair places that refuse to even work on push gas mowers. Gas weed eaters are the most disposed of units out there. Small engine places have pretty much priced themselves out of working on anything except higher priced riding mowers. With the advent of the lithium powered weed eater,I can see the day gas powered weed eaters are no longer made except for lawn maintenance businesses,ie, professional grade models. even then,those will be disposable as well. I myself have the ability to referbish these discarded mowers and weed eaters and although I dont make a lot of money,I do sell them to support my other hobbys. I can relate to your repairing tv's. You are aboard a dying business boat and it is sinking quickly. Sears by the way,throws out lawnmowers they get back under warrenty programs. They dont even bother servicing them should they get returned under warrenty. Its cheaper to issue a new mower than to fix them. At least in our town where they closed the service center they do.
Aside from everything becoming disposable I think the quality of many modern day appliances has gone down hill.
+Grants Pass TV Repair I dont argue there. As a matter of fact most are not ment to last more than 5 years max. I have a friend in electronics that told me they were told that as far as design and longevity is concerned.
But the price as well. I remember when we bought a video player, not the recorder, it cost us 1200 DEM (Deutsch Marks) which is today around 600€ and then it was HUGE amount of money. Not to mention PCs and prices. Quality is low, but the price is low as well. I mean, until you pay top box for something. Ppl expects they pay really low price for a TV and then they expect it will be perfect lasting for 20 years.
Shopjimmy had a video to turn the backlight down in tv settings to prevent early failure. I guess this would not drive the leds as hard but wouldn't picture quality be affected?
+Beau Michna after an hour watching, you wont even miss it, as long as it isnt at max anymore, 85% will possibly increase lifespan for a year or more. EDIT: well.. cant quote me on that, i dont have two identical tvs running all the time to test that, however in theoretical theory it should.
+Beau Michna Yes the picture will still go darker if you turn down the backlight adjustment, but on the LG TV I tested it did not effect the backlight voltage in any way. Apparently on some LED TVs the brightness of the display can be changed by the display pixels regardless of the brightness of the backlight.
+Grants Pass TV Repair even through the service menu? I didnt know that. thanks for the info.
+Grants Pass TV Repair Thanks. So if the voltages remain constant on the backlight, it would be pointless to turn down the backlight, right?
+Beau Michna voltage isn't the issue, current is. as he said, SOME TV's will be pointless EDIT: they most likely use PWM
I've not run into any bad LEDs yet. There are a lot of 32" Emerson models with bad power supplies and larger 60-70" Vizio models with bad Sharp LCD panels but no LED problems.
How often do you repair TVs?
I get a lot of broken ones from Goodwill but it's mostly bad capacitors except for the ones mentioned above. There seems to be no way to fix a Vizeo except to buy an expensive new LCD panel, a lot of people are taking them apart and selling the boards on Ebay but the LCDs seem to all be bad or broken and I haven't found the problem on the Emerson PS's yet even though I've tested almost every part on the board.
Since you hadn't seen an abundance of TVs with bad LEDs I was guessing you probably didn't own a shop.
Not for a while. I tried it once and while everyone in town has broken stuff, they don't want to pay anything to get it fixed and would rather it be done for free so I never made any money. I also tried PC repair too but could only make about $3.00/hr so that didn't work out too well either and wasn't enough to even cover expenses.
At one point this trade paid far better than it does now, and many shops are being forced to close their doors. I'm only surviving because I'm doing home service calls, and antenna sales and installations.
How much voltage required for LED Strip
To answer your question on LED backlight voltage it depends on what TV your talking about. It can be different on different TVs and models.
40" LED MODEL CV628H-B42 (CHINA MADE)
LED backlight
You know Dave....after being in the bizz for 35 yrs, I also found myself telling custs to buy contracts and also that manufacturers should build them better etc.....Then I realized, we are basically pushing ourselves further OUT of the service bizz by wanting a better built TV or Serv contracts......After all, we were there to repair these faults etc....! Yes, they would be a better TV if they were built better, and more likely to sustain a repair....but, ultimately, we got pushed further out of the servicing end due to the cheap throw aways AND THE SERV CONTRACT that end up just sending the cust a new TV .......I guess morale of THIS story, the servicing end is all but gone and I regret not taking that state job in lieu of staying in the repair industry only to find that I wasted 35 yrs and now had to find another job instead of retiring from electronics with something......
Dave, cut your losses in this bizz and get out before it eats up anything you may have gained.......I let pride get in my way.....should have got out in the late 90,s when I started seeing things getting cheaper and more rediculous to repair and replacement parts were so expensive etc.....
You are smart, branch out of that end and put your talent to another area of electronics, medical, commercial etc.....
TY for reading my rant....good luck.....Frank..!!
Good advice Frank. I've already started doing a variety of other things aside from TV repair. The nice thing about our skills is we are well primed to work in other electronic related industries. I think people who can think outside of the box can always come up with some creative way to earn a living,
Take care.
Frankie, you're absolutely right. Anyone wishing to be a top-notch consumer electronics tech had better investigate the cost of up-to-date test equipment and how long it would take to amortize the cost. As an independent repairman this will never happen because technology changes so fast the equipment is basically obsolete when you buy it.
Franchise dealers, like new car sales and service, are constantly supplied from the manufacturer with updates to older gear; finally replacing it with newer stuff. All this "newer" technology comes out of the dealers' pockets, so you now see why a $12 an hour entry level mechanic costs $80 an hour (or more) to fix your car.
rayford21 excellent points..!!
Over powered and not enough hear dissipation. The double stick tape doesn't conduct heat very well.
Leds have a phenomenon known as hysteresis, avalanche, and propagation delay. Avalanche being bad and hysteresis in being a characteristic in the theory of operation, and propagation delay of forward voltage in series. For this alone I don’t recommend to test leds with ac voltage.The leds resist to turn on but when on resist to turn off, to overcome this a certain amount of inrush is needed to overcome the hysteresis and the minimum forward voltage drop needed to activate the diode junction and if there is 10 leds on a series this base forward voltage drop adds up and is very similar to a filament starting up. A practical dead short at first. The propagation delay increases with more leds in a series. Some modifications have the test points paralleled to other leds test points to in a sense make them a parallel series ladder.
In some models of tvs that offer a stand by mode or fast boot these tvs supply a minimum amount of power to keep the leds above hysteresis this may use more energy but in my opinion saves led life as they are always on at a minimum and are ready to be ramped up.
Leds in a parallel circuit obviously do not have propagation delay and way less hysteresis.
I have had the misfortune of damaging an LED strand when using AC source without a series resistor due to excessive peak reverse voltage, but considering I'm now using a 10K ohm resistor in series with my LED strand in this video, that means my current is down to 0.012 of an amp, and that's not even including the additional resistance from the LED strand. I'm no engineer, but at such a low current, do you think I'm likely to cause any problems to my LEDs from to high of a reverse current? I haven't encountered any problems doing this.
LEDs are not designed to run in reverse polarity. Even if the current is less than test forward current, reverse current can damage leds as they are not rectifier diodes or a unipolar device. Granted a average spec will show say a max reverse voltage of about -5 per led in 3535 as to allow pwm at 100hz or higher. Most outlets or line frequency is 60hz and this is where it may be damaged and the main reason not to use line power. The idea from pulsing is to achieve a higher power output at lower junction temperatures as reversing the led just right after peak pulse pulls the heat away from the die.
I get what you're saying. Thank you for point this out. I'm going to do a few tests, and if I see the LEDs are damaged I will edit or remove this video.
Here is a test I just ran on what you said. czcams.com/video/BrdmIrAvLxw/video.html
czcams.com/video/BrdmIrAvLxw/video.html
Thanks Dave. I would warn them beforehand that the screen may break. It kind of defeats the purpose of being in business if you keep forking out money to customers.
+Robert Calk Jr. That's a good idea to warn the customer. Having to pay for a screw up thats almost unavoidable didn't seem fair, but I felt as though I could have been more gentle than I was so I covered the damages.
I have a friend who has a Vizio flat screen tv that has the ccfl for back light and still has a good picture and it's going on 11 years now and has a led tv that's going on 5 years now and still has a great picture
I think the average life expectancy of a modern LCD LED TV is 4 to 7 years, so 11 years is great. I think CCFLs probably outlast most LED backlights.
I heard from somebody that LEDs are damaging themself after exceeding 60 degree celsius on PN junction. If those LED had some heatsinks they could last longer.
+MDF RESCUER I'm sure heatsinks would help, but on some of the LG Models where the current is almost triple at the first 10 seconds of start up I'm not sure how much that would help.
+Grants Pass TV Repair I wonder if the problem is the sense resistors in the backlight circuit?
I suspect it's probably a design flaw.
Another thing which I heard about LEDs that they draw more current after they are getting old.
They can short out or become leaky like any diode, so it makes sense that they may draw more current as they age.
Hi i enjoy Your Videos. i have a Naxa 55 inch TV
i wonder if You are able to guide me through a specific problem i am having with a TV i have
My Naxa NT-520k board # is (CV3458H-A50),Passes the flashlight test, so i rule out the T-con Board yea? The TV has sound but no back light.i do notice that i get approx 140V to the leds so the tv goes out eventually when too hot.when only 120 is needed.how can i safely drop the voltage with a resistor without getting too hot? i want to lower the voltage from 140 to approx 120v. do Yo have a small schematic of a regulator i can make for it or (see below)
I also ordered a LCD Driver Board, Universal 10-65 inch LED LCD TV Back light Constant Current Driver Board Boost Adapter Board for LED TV but i have no idea where to solder the input voltages fro the Naxa Board
i can not find anyone with a English speak video help me install this Board, other wise i want to add a resistor and maybe heat sink as the resistor got pretty hot but kept the TV back light
Thank You
If it passed the flashlight test I'd guess it's your backlights. All it takes is for One or more LEDs to go bad for backlights to all shut off, If that's what it is all the backlights need to be repaired together. If you just do One backlight the rest will soon go bad in a short time.
@@GrantsPassTVRepairi used the over head lab light instead of flashlight and yes it passed the test. so it not the T-con board.
i had use the multi purpose tester at first without digging deep into the led strip section. (that would be my first time if i had to) it has only 2 leads it lights up bright and reads 120 volts (using that tester)
but i see 140 volts with a multi meter going to the leds.. and was hoping i could reduce the voltage and let mom watch tv on that a few more years.
never done a led repair.(yet) i thought because the leds lit up using the multi purpose led tester tat the leds were ruled out also?
if You know a way i can use the resistor or the Wendry LCD Driver Board, Universal 10-65 inch LED LCD TV Backlit Constant Current Driver Board Boost Adapter please let me know. even if i chance the leds eventually dying in time.
@@sweetleaf7751 Did you actually see every LED come on using your tester, or are you assuming they all came on? Even if they do all come on I know of one instance where the LEDs all came on, but because one of the LED strips had a defect it drew to much current and sent the TV back lights into shut down. Adding a resistor to lower current will probably be an problem since there is a feedback circuit that can sense when you aren't drawing the correct current and shut the TV back lights down. I know because I've tried what you are saying.
@Grants Pass TV Repair First let me start by saying thank You for your kind reply. and Yes i know you had used a 10k resistor in my case i used a 100 ohm on ground between the board and one wire that was ground and it stayed on for quite a while i was surprised..
yes i assumed the led strip was working as so i was informd that if the multi purpoe tester reads 120 volts, and lights up the back light then the strips are fine and You dont have to dig any deeper and they suggest that it is the led drivers fault? If i am wrong let me know as i recently gotten that tester KT4H SID LED Multipurpose Tester and i am a first timer with that device. though i rely more on meters then that.
i been doing stuff liek this since i was 6 or 7 but never really understood electronics much till a few years ago o i am still learning and have my Lab all set up :)
if there is a email on your site i would have sent you a message there.
@@sweetleaf7751 Due to the time involved It's best to call if you have any further questions.
I find most of these LED's have three connection points. Does anyone out there know where I can find a diagram(s) that identifies the pin connections to the LED's?
I know, I know,.....DUH! Please forgive my ignorance.
I hate glued displays on tv and smart phones this brand doesn't like us to repair it on 2016. and the worst thing is they claiming the led never dies
I buy some of this led from eBay and the work.
Your a good man giving up 200 when you take the risk to do the repair i my self will not i fix phones too and they seem to put glue on some parts on purpose and you may break a ribbon its not our fault get a damage waiver signed i do
Sometimes it's hard to determine how much responsibility I should have when a customers display brakes. In this case I felt as though it was my fault for being in a hurry.
I ruined my reflector trying to get it off of the back of the TV I could get to the LEDS to test them. The LEDS are good but TV does not work. I have all replacement boards also. I will never buy a LED Tv again. The LCD supposedly last 100K hours before the lights burn out.
If you're not going to buy an LED TV again what other options do you have?
@@GrantsPassTVRepair LCD Plasma ?
@@GrantsPassTVRepair Nothing is made to last anymore. I do not miss the boat anchor TV's but, the new technology just does not last but, it certainly is overpriced.
Wouldn't it be better if the strip was stuck on the back of the metal, outside with the led and disfuser poking in through a hole to inside. Or the difuser inside and just a tiny hole under it where the leds stick through from outside to inside. LG can have my idea for zip (or a couple of 65s if they're feeling generous).
That's what I was thinking when I mentioned how they could have made the LEDs accessible without having to remove the display. It could have been made in a way that would have been simple to troubleshoot and replace. Perhaps they may not want to you repairing these Televisions..
I have 15 of these ready to pull down ranging from 42" to 55". All abandoned by the owners for spare change, and you can still see the image with a strong light and hear the sounds. Two things happening here. First, owners have been taught to discard any thing over a year old (so they can buy the lastest and greatest) and second, I'm not confident about any long term fix because the other leds will probably die.
I understand your concerns. I would also be reluctant to repair a Television you can't expect to last. Welcome to modern day TVs. Replace every year or Two and your good too go.
I've been looking at the leds in those LED light bulbs as replacements. They seem to run at higher temperatures and are fairly cheap to get yoiur hands on to try. I've been looking at BigClive's teardowns while he's been playing around with them, and it occured to me that these may be a better source of leds for replacement. Not sure of the color spread yet though.
In your 120vac tester, think about having 4 by 27k reisiters instaed of one 120k resistor, I'm not sure the internals of one resistor should be subjected to that type of voltage if you feed a short (or you). Flash over might occur. Here where the mains is 240vac, your circuit would be a death waiting for you device.
Asab
I disable Adblock on youtube. Because youtube is too much important for me
Instead of a resistor to limit the current you could use some of those constant current diodes.
+Arnþór Gíslason Sounds like something worth looking into. I didn't kknow there were constant current diodes.
It's just a fact that manufacturers don't want their products to last forever. That would dry up their revenue stream.
Call it a conspiracy theory if you like, but manufacturers engineer their products to a certain lifespan.
Sad but true. One of my customers had a Curtis Mathes CRT TV that lasted over 30 years. You will never see this with one of the new TVs.
because they are driving them to hard ??? ( Your knowledge of English is poor ... You should learn the difference between TO -TOO and TWO---- It is because they are driving them too hard.....
Thank you for the correction :-)
Another nit-picker that prides himself on pointing out peoples' spelling mistakes.....get lost!
Isn't it annoying when people can't be bothered to use punctuation correctly?
Three question marks, three full stops, four hyphens, and no capital letter at the start of a sentence, which one should never begin with "because" :-)
Seriously though, those ESR multi-function meters based on the ATMega328 chip-set are very good for testing capacitors, diodes and transistors. They will tell you the forward voltage, reverse current and junction capacitance. A diode may test correctly on a multi-meters' diode tester, but the reverse current (Ir) and VF can start to go out of spec on a diode that might be breaking down early, or late. Increased Ir can also indicate a failing diode.