More METHODICAL Fault Finding, Samsung LED Monitor Is Faulty & We Have No Schematics. Can We Fix It?
ฝัง
- เผยแพร่เมื่อ 13 เม.ย. 2022
- LER #227 Here we have a faulty Samsung LED Monitor. Let's reverse engineer the PCB and see if we can work out what is wrong with it.
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Thank you
Richard
It's interesting how closely electronic fault finding is to medical triage, as in medical school you are taught to cut away possible diagnosis through the symptoms rather than trying to match the symptoms to a diagnosis, a good attitude to have. I've learned more through your channel than anywhere else, thank you for your in depth videos.
I totally agree - eliminating as many possible causes as you can will take you a long way towards fixing stuff 🙂
Im 60 yrs old and trying to learn electrinics. These are great PLEASE do more. Cheers Rich
this is why I like your channel it's down-to-earth electronic repairs. We all make mistakes as technician that's why we learn, I learnt from your mistake. I hope you make a lot more :-)
I just stumbled upon your channel a few days ago. I have to ask (Rhetorically): Where have you been all my life!? Thank you for your generosity to share and teach electronics in the manner that you do! So many people try to present a perfect image of teaching that comes across so rehersed and unatural to the point of being offputting. There is something very noble about admitting human imperfections we all experience from the arts we strive to perfect on. You without question have an artistisans talent. I am very thankful you are sharing your wisdom with us. I believe i have found my mentor. I regret i only discovered your videos now. Please keep teaching! It is rare to find such wisdom, insight, candor, passion, and HONESTY like that of your manner on youtube. You Sir are a Good Man and an Excellent Teacher. I wish that i could shake your hand. Thanks! You have rekindled my interest's in electronics repair.
Funny enough, one usually learns more from mistakes. Maybe repair channels should show more of their mistakes.
Anyway, thanks for the video.
Happy to say I called it. An important clue was the pulsing failing startup. That indicates a converter of some sort.
Thanks for putting in the effort to educate the masses. I've only just found you and have learned so much in the past few days.
Keep them coming!
Thank you Sir. Being honest is fast becoming a rare thing these days. Much respect. All my best.
Spot on attitude. Also you are amongst the best techs ive come across. Learning alot from your videos , appriciate all the work you put into getting your knowledge out to people like me .
Professional troubleshooting electrician. Troubleshooting is a skill, and you improve as you see more problems. Repetition also makes you faster.
Never be discouraged in your personal journeys to find solutions to your problems. Gaining education, experience, and mentors/coaches are all important to succeeding.
This is far beyond my current abilities, but is still very interesting. I’m just first learning the basics. To see what things are like at this level is helpful.
G'day Richard. I really appreciate the content on your channel. It is so helpful how you insert your ponderings upon reflection and dive into the thought processes before returning to the octopus in hand. I reckon you would have made a great teacher or lecturer had you chosen to do so. I think you might be turning a lot of parts changers into Technicians with your great way of imparting your knowledge and experience. Two thumbs (and big toes ;) ) up.
Its been awhile since I've been down to component level, mostly deal with large system faults these days, im enjoying the well needed refresher and as a young definitely learning a thing or two. keep up the great work 👍 👏
I remember when I was a young tech doing in home tv repairs, An older tech saw my frustration on certain repairs and told me, In electronics 2 plus 2 doesn't always equal 4. Ten percent of the time , no matter if everything I did to repair the problem was correct it just doesn't work. Even if he's not right, it surly helps with your mindset instead of getting frustrated. Thanks for the great videos.
Thanks very useful, I see the dirty meter works well.
Thankyou for sharing your knowledge and more for showing the mistakes along the video! Greetings from Argentina!
Making mistakes is an integral part of the learning process and comes with the trade. Much kudos to you mate for putting that in your video!
Breaking down panels has so many caveats. The panel connections are major drama queens, especially on the samsungs where they run down threes sides. But the worst part is when you have a 65" display, you put it back together only to find that a hair got between the plastic sheets, or even better - when little flies somehow get squashed in there.
Off to work now where two LG tellys (a 46 and 55 inch) await a backlight replacement.....the joys of a monday morning, eh? 😎
Thanks for posting and a nice channel you have btw!
Getting things wrong is the first step in getting it right. I can't imagine how many mistakes I made and how I learned (or not) from those mistakes while I studied electronics in the 90's. I remember the importance of placing capacitors the right way round when I accidently launched one to the roof by it being the wrong way round. We were learning building power supplies and found a stash of big electrolytics. I was monitoring a friends circuit while I built mine. I heard a hissing sound, looked to my left to see a poof of smoke and the thing literally take off! It was hilarious but the supervisor didn't think so lol.
I do have one question if I may ask. I have an LED backlit monitor which only lasted a few weeks before the backlight stopped completely. I remember it failing in one corner first before the whole thing failed. I kept it in the hope one day I would be able to repair it. Where would be the best place to start fault finding do you think, like you did with power supply or the LEDs themselves as dead ones may have messed up the whole circuit. I'm a bit old school with electronics I'm afraid. I prefer to build clocks from crystals, dividers and logic gates. I am not into microprocessors. I prefer the tried and trusted 74 and 40 series chips. You have more fun that way and always make mistakes but like I said, finding the problem and resolving it is probably 90% of the project :)
So glad I found this channel, it is so refreshing to see a real person do real electronics (there are a few on TH-cam). I subscribed :)
Without power applied you can check each led. Do you want to do that?
You have a new subscriber. I am just learning self taught, I don’t absorb a lot from people catering to an audience of people who know a bit more and thanks for that! I learned a lot from your explanation of how u didn’t get it right the first time.
You're an awesome teacher Richard. I love your calm, honest and methodical approach. Thank you for the effort you put into these videos.
I’m sure you are correct about some creators not showing their mistakes… personally I include them in my videos, and even publish videos from time to time where I failed to fix something.
This video was really helpful. I have a samsung SD590 type 24 inch monitor that produced flickering black bar. The controller was almost same. Bit moved on the PCB here and there. Was remotely ok for a day when 50% eco mode was put on. I had a suspicion that the issue was the backlights LEDs. I used your video as a guide and managed to verify the leds ultimately by testing them after disassembling the whole monitor. From the backlights 36 leds the middle strip has failed led in position 14 and 24. All I got to do now is to source the leds online and change them out. Thanks for the good video pal 👍
Another great video, love the analogy of the building blocks, I've been using this method for years as a boiler service engineer for a major manufacturer but hadn't thought of it as blocks, your right.As for other creators on TH-cam " it's all in the edit " 😆
Cheers, nice to see you enjoyed the video
Further to my previous, i'd just want to say thanks again. I don't blame you for avoiding Displays! The packaging is a nightmare!! Sadly, they tend to be the most common to have a fault.
You are most important, that's better than the best electronic guy...love this channel
You are a kind hearted innocent technician.
Thank you for your channel and videos. Truly a godsend, I had an ephinay watching this one and the last one I watched. It's finally making sense
same.. the jigsaw puzzle is slowly, but thoroughly, coming together. :)
First of all, the way that the world is constantly changing, modifying, upgrading, inventing, I think someone who's willing to examine things from a framework they already have, knowing they could be wrong, is more apt to be able to adapt to change, than someone who becomes rigid and pretends that knowledge is a fixed monolith. So good on you for being adaptable. Secondly, your speculations help us see your thought processes. It helps build an appreciation for constructing one's epistemological model. You're similar to some other youtubers I've come to appreciate. mustie1 is a good example of both entertainment, and learning. He takes a similar approach to automobile and small engine diagnostics you do with electronics. Not knowing what you've got is that adventure in exploring the unknown. And I think there are plenty of those frontiers to play in. Thanks.
Great video. Thanks very much.
Hi Rich, I like the way you present your videos and are very open about what you do, including incorrect assumptions.
Not many presenters will show their mistakes and they get edited out in production, its nice to see that you are confident enough to show them.
Its very true that after time we can look at a board or system and identify typical circuits right away.
I've been working on electronics since I was 16 and I'm now 65 and retired but I'm still learning and still enjoy the challenge of repairing things
regardless of their complexity or simplicity and it saves them from the landfill too !!
I have tested LED strips and replaced the LED's in a couple of my repair videos on my channel.
I too use a back-light tester for fault finding those LED strips and the fault modes can be shorted, open circuit or intermittent.
I also show a hotplate tool I use to heat the strips from below for LED replacement.
Sourcing the correct type LED's can be a challenge, and sometimes strip replacement is the better and easier option.
What I find most often is the back-lights are running at 100% brightness and this kills the LED's within quite a short time.
I recommend that after replacing the LED's or strips you turn down the brightness to about 50 - 70% of maximum.
This will extend the life of those LED's and not overdrive them.
It's such a pain in the butt to dismantle the screens that the time and effort involved makes it often impractical to do this for anyone but myself.
Its frustrating that the manufacturers seem to design these back-light systems to squeeze every single lumen they can out of the LED's which
can often fail within a year if the brightness is not backed down to a level that will not stress the LED's as much.
Thank you for your videos Rich, they are very entertaining, oh, and I was born in Birmingham, UK, so hearing your accent is always refreshing as I now live in the USA.
I have used my preheater plus hot air to change just the faulty LED(s) in the past but it never seems to last more than 2-4 weeks before failing again. Sometimes with other LEDs and sometimes with the one I changed. Turning down the brightness would help. Like you mention (and I showed) it is definitely a pain in the ass to dismantle the screens, and the larger the screen the more hassle it becomes. It's good to hear you are still enjoying the challenge of fixing stuff in your later years, as am I. I'm no medical expert but keeping your brain active in this way is probably a good thing. I'm not actually a Brummy, I'm a Potter. Actually some people even think I'm a Scouser. Like you, I eventually moved away and live in the Canary Islands. The locals think it is very funny if I say 'Hola Pato' to them!
@@LearnElectronicsRepair Yes I realize you were not a Brummy but just hearing the accent always reminds me I'm an ex pat and its refreshing. Thanks for the reply. 👍
The ones I watch are like you and will readily admit they get things wrong, even to the point of admitting that a 60% success rate on fixes is no bad!. The ones, like you, that want to teach others, go out of their way sometimes to show that mistakes happen, that very often you will have to be willing to revise your thinking if you want to achieve success. I just subscribed to your channel because of your pragmatism and the way you help me to explore the circuit board.
I appreciate your lessons, I'd rather you be wrong and admit it, then a perfectly edited video bud. That's real
You're correct with your analogy ❤ greetings, keep up the good work
I think yours is the better channel by far. I'm very interested.
God forbid you'd have a dirty multimeter! People when you actually work everyday and use tools they get dirty as do you. You can't clean everything everyday or you'd get no work done. I clean multimeters and tools when I get a quiet period otherwise I'll continue to work away as they are. As for my work van.. close your eyes when I open the side door🤣 Great video as always love these👍
Haha. Yeah I agree, however I took the yellow plastic jacket off my Fluke 79, took it home and then asked the wife to wash it for me! 🤣
Problem solved
Cool stuff..thanks
Sometimes it doesn't matter how good a tech or any other tradesperson is at what they do trolls will always be trolls, what matters is the honesty. It takes a great individual irrelevant of what their job is to be honest and admit mistakes made after all as you said everyone makes them and indeed not all creators show fails 😁.
Please keep doing what you do Richard as your fantastic at it in every aspect for me and I even preferred the "yeah" at end of each sentence, think it's a UK thing yeah 😁.
Nice upload many thanks.
Ahh so you liked it Yeahh!!!! LOL 😁
Magnificent video. Thank you for making it.
At 25:48 I would have liked to see the voltage supply to the LED's, on the board, without the LED's plugged to the board. I also would have liked to have seen the effect of the LED's when you connected the LED tester. Great videos 👍 Keep them coming Thank You.
P.S. I see you showed the LED test at 33:00 👍
I found a circuit online to make a backlight tester using capacitor droppers.. Only problem is not mains isolated. But works really well.
That sounds a bit dangerous, capacitive droppers should only be used to power very specific circuits from the mains , never for general use.
Thank you Sir..
Thank you for helping us Learn to Repair by unselfishly sharing your knowledge!! God Bless You for that!!
I am working on an almost identical Samsung board...I measured 14 volts at VLED just like you did. I removed the LED strip and tested each section with my power supply...using ~36v, each section tested perfect.
The monitor started showing symptoms of trouble when the lower third of the backlight would start to dim out. After removing power and reinserting, everything would work good until i had to repeat this cycle again. Eventually it just stopped all together.
Do you suspect the PWM circuit is faulty in timing the MOSFET/COIL/DIODE boost circuit?
Thanks for your advice in advance.
Thanks
Adults make mistakes and do their best to correct them
That is just about the best definition of having children I ever read!! 🤣😂🤣😆
Fantastic !
Hi richard hope you are doing well :),
sorry for not engaging a lot last few weeks, the new job is taking a lot of time to get used to but it's starting to feel easy :P.
i total agree with your view on how your experience makes you see parents after a while , and you know based on past experience what components are quit fast .
Keep up the good work richard
you are growing to fast , you wont give me enough time to make you something for 20k subs mark :D
As assume those are patterns not parents lol
@@LearnElectronicsRepair Lord XDDD yeah i leave it in looks funny :D the dam spell checker got me :D
@@RetroUpgrade The damned spell checker got you twice ;)
@Dennis Jones XDDD i will blame it on lack of sleep - you didn't see anything wrong 😂😂
Its my dream to get into this kind of work one day
"Take On Me" is a great song, one of my favorites. Anyway, you do have to be careful when looking at reviews on Ali Express. I was looking at some things the other day and noticed that in the reviews, several "individuals" supposedly from various different countries used the exact same oddball phrase word for word (whatever it was, can't remember), and also used the exact same misspelling "Recommand!" when they were recommending the item. Beware the review bots.
Hi Richard you can the lcd work if you short the open led. You can fix the monitor . It woul not realy visible if you do that. Best regards
Steve
Excellent 👍 I like how you don't give any power to the trolls.
hi Richard. If you're looking for content to create, how about doing a series of videos about how to read schematic and explaining how the circuit works, how the current would flow through each each component etc this is a vital aspect of electronic repairing and I think many of you viewers would be interested.
Thanks for the suggestion, I'll keep it in mind 😉
Can you suggest a desk power supply? I have 2, 30 volt 10 amp supplies. I was watching you use yours trying to find a short and you input .8 volts and 5 amps! When I set mine to .8 volts I cannot get the amps to go above .1 amp and I cannot get any heat with that. My units are very heavy so they have large transformers in them. You mentioned that if you got another one you would want 30 volt 10 amps. Can you mention which one you would buy? Thanks and I hope you got your cup of coffee.
Seems a lot of work for a relatively cheap a Tv? How much time would this take you without making this very excellent tutorial, and how much would you roughly charge for this type of repair? My dad used to repair tv’s for a business for years before the invention of LED/LCD TV’s, he tried to teach me electronics when I was a teenager but wasn’t ready, now at 44 I want to learn! I’m a field service engineer working on automatic doors for the last 15 years after completing 9 years in the RAF as a plant fitter. This is my first watch of one of your videos, I’m going to check out your catalog now. I love your tuition and your honesty. I can see you have a vast knowledge of fault finding and can still admit your thought processes were incorrect at the outset. I tell my "new" engineers that your always learning and will never know everything about all the equipment out in the field,we’re all human. Keep up the great work.
Love it
Cheers !
I am curious about those LCD screens where there's a finger size black spot issue. What's the problem there and can they be fixed?
Getting it Wrong learning..too
Hi, may I ask what the purpose of the low value resistors is?
heya I gues to tv repairs take a lot of space and I done have that so will see if I'm gone do those
Hi buddy. Thanks again for a really interesting video. Thanks for taking the time to make it and share your knowledge. :) may i ask, if a LED in series with others (aka strip) breaks down, can it not be possible to A) remove led, or jump led, and short with bare solder from previous to next Led?, or B) replace a small value diode with same voltage drop? Thanks. Rob.
If we are talking about LED back lighting and similar applications then usually the answer is no, because the chip that is controlling the LED current is handling several LED strips at the same time and if one has a different voltage drop to the others (outside a certain close tolerance) then it will sense the imbalance and just shut down, or they will all flash on and off.
@@LearnElectronicsRepair I get ya. the brains (chip) are P.O.S.T ing and rejecting. Thanks. Can sometimes be useful trick though? I mean for decorative strips i suppose?
Huh, I guess the high current just shorts the failed LED? Seemed to be open when you checked it with the multimeter.
Great video, where about in Spain are you?
Gran Canaria South, Maspalomas
with parallel series on single channel driver you probably should be replacing all of them, there is no telling how much current imbalance reduced whatever life they had left (and since one failed it wasnt much to begin with, least it was a qc/binning error)
Turns out there is one single LED strip and I'm replacing it.
How to determine if theres a problem with the IC?
I have a heap of bung monitors (from a radio station that leaves it's monitors on 24/7). It's sad but in the real world it's just not worth the time to fix them. My time is more valuable than the cost of buying replacements.
Any guides how to replace front screen polariser film? I mean how to remove glue new film without dust?
these are laid bare. they are just stacked. the clipping on the frame brings the the tension required. The plastics used, at the time of moulding have an "anti-static" additive. Avoid human skin contact directly as it leaves oils, and wear a static strap to ground if you're not sure of the sensitivity of the components!!!
An awful lot of tricky labour
Magic is mostly smoke and mirrors, but I don't need a mirror to find the smoke💭🔥
so this LED line is responsible for the whole Backlight? Or is there another one at the other side?
And did you ever had broken LEDs from the ScreenLEDs (Dont know what they are called)?
Thx alot, really interesting
In this particular model there's only one led strip for the whole screen! Actually most monitors have two strips viz one on each side!
A beautiful day starts with watching wonderful videos like this. I have enjoyed watching, thanks for sharing . a fellow creator.,,.,.,.
OK just about to watch it but I like to place my bets: blown capacitors
Why didn't you replaced all 3 led strips, as other two probably weren't in tip pop shape also?
There was only one LED Strip in the monitor
I've got a Samsung curved version to that monitor slightly larger from the tip dumpster, there was nothing wrong with it at all, the last owner must possibly have thrown it out just because of the faulty 12 power supply.
One question! Why didnt you desolder number 16 led and closed the circuit? That would be a fix!
Since the bank of LEDs lit up with testing, it appears the burned out LED had failed short. So, removing that LED and inserting a jumper to close the circuit would have had the same result.
My wife already taught me about fault-finding.
You need much more then a led tester, a pair of gloves, a dust free place to work, suit for clean rooms of some sort. Else the image will be much worse then you can hope.
Strangely I haven't found that to be a problem (yet) and I did fix quite a few TVs
@@LearnElectronicsRepair Strange, indeed fingerprints on polariser, diffuser specks of sut can ruin whole repair. Ans it is impossible to clean the diffuser, even with distilled water it's mission impossible.
@@juliusvalentinas OK I hear you - let's see what happens once the LED strip arrives 😉
@juliusvalentinas -not sure i agree. i do understand what you say. They can be a bitch and sometimes very finicky. but low-end consumer electronics are far different to lab and commercial eelctronics. for a start, almost everything in commercial electronics is like airplane.. Highest Quality components, and certainly a form of redundancy for each critical component. I think this particular type of device is far from commercial/industrial 'spec'. Best wishes. Rob
Someone can think that can bypass the failing led, but the result is the increase in current/led and consequent new failure in short time.
R.F. diagnosis, now that is the Dark Arts.
Given that multimeters perform diode testing by using constant current, as shown in this video during that strip testing, the discrete diodes did not reveal the same forward voltage drops on the multimeter display.
Since they are connected in series, theoretically, they should have almost the same voltage drops being supplied by a constant current source and also they should emit light in a similar or almost the same intensity, which did not happen here.
In conclusion, this behaviour, either seeing it electrically or optically, reveals the worn out diodes which should be replaced. The rest of them, giving identical or very close to each other forward voltage drops when being tested (excluding their aging) can be considered as healthy.
Having myself a bench power supply, I prefer making these discrete diode tests using it, having adjusted beforehand to 5V and 50mA and watching its voltmeter display for each diode test, in order to evaluate the overall situation and then judge the action to be followed in a more solid base.
Of course, replacing all the strips at once is the easiest way, but still the costlier one for the customer...
I totally agree. Actually I think the low current of the diode mode on the multimeter shows the tired LEDs better than the higher current of the backlight tester, So both methods work well in together 🙂
@@anshadedavana I totally agree with this argument and believe that every technician has experienced such kind of failures and relevant returns. Nevertheless there is a big difference between the cost of replacing all these four diodes of a bridge rectifier, instead of one or two found defective and that of replacing all the led strips for the shake of two or three defective diodes.
The last wholesale replacement I did on a 32 inch old LG TV, had a spare parts cost of 60€. Therefore I asked the customer about his intentions on that repair, given that another similar repair had been performed previously on that same set, which kept it alive for only one year...
The previous technician had replaced only the three of the six strips and I found the new failure on one of these which were not replaced (which works in favor of your sayings).
Long story short, I honestly let the customer to decide about the type of the repair he wanted, explaining him the case in terms of both the cost and quality.
He chose the wholesale replacement and only then I proceeded on it.
My point of view is always to explain the customer the choices he has, of course supporting the best quality on the repair to be done, but he has the last word as regards the cost. If he prefers the cheap service, he must simply be informed that he will soon ask for a new service...
And then, there is no way that the fault can be yours...
@@anshadedavana Even worse things happen...There are technicians who simply short circuit the defective two or three leds they find and charge a repair...All of it depends upon one's own character/personality...
All I have learnt from this channel is that once a complex device stops working...throw it away and get another one.
I have bought a 5750-APU instead of a GPU. If I buy a GPU is will be a near dead bit coin mining GPU for dirt cheap. I'm not prepared to spend anything on a GPU.
All the creator I watch make error, like a lot, nothing bad about that ^^
Yes, clean your DMM you mucky pup! lol Great vid as per.
I have a Samsung 21.5" monitor is a model Code LT22B350ND/ZA, with a power supply model PSLF5650501A BN44-00505A. I am trying to find schematics for the monitor. Does anyone have this documentation or a source for it?
Hopefully, 14V on input of LEDs is due to the time that passed after attempts to light LEDs from a chip. I can't comprehend how can 14V be on LEDs that need almost 100V
Me neither
If it doesn't work after replacing the LED strip I will have to work it out on a part 2!
@@LearnElectronicsRepair The 14V is just Vsup passing via the coil and diode to the load. I think the controller at startup is sensing the wrong current and stops pulsing the mosfet gate.
I unpluged my monitor butt forgot to unplug the power suply plug pulled it on it then i unpluged it butt when i pluged it in in the other room it stoped working and is dead now the power suply stil work though but my monitor stayes dead
❤🌹
It's a shame - for me, anyway - that you have selected a monitor with an external PSU. Using a device with an internal PSU would be more helpful as then you could show how to assure the PSU's operation as well as the other parts of the monitor. Testing the reliability of an external PSU is so easy to do, you just find another one and then you're off to the races.
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Cunning Vulcan logic….
the accent was too British for my ear, even though i activate the subtitle, youtube it self struggling with the accent.
nice video anyway....
I'll do my best not to speak English like an Englishman LOL I think I am getting a bit better at doing that
If you don't have a dirty multimemer, you aren't using it.
4:01
Just like a woman unless they are intoxicated, then its easy
11:20 One thing I found out about programming and electrotechnics community that it is so full of deprived and ego masturbating trough other people's humiliation bullies that this guy is ,,forced,, to put emphasis on fact how ,,wrong,, he was.
For when a video in Spanish?...please if you can
please use Indian English
to gud mi g lov it