Master Electronics Repair !

Welcome to Master Electronics Repair! website.Here you will find:Service Modes, Circuit Diagrams,Service manuals, Firmware Update procedure, Disassemble procedure, Universal remote control setup codes, Troubleshooting, Diagnosing, Measuring, and more.... of many of LCD/LED TV/Displays,others various electronic apparates,trough many technical notes and tips/tricks to help repairing/fixing Troubles/ faults,for electrical technicians.This site helps you to save the Earth from electronic waste!

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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Note that if you don't find what you searched for, try it after a period of time; the site is a never ending job !

..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

©2010, 2011, 2012, 2013, 2014 Frank Sharp - You do not have permission to copy photos and words from this blog, and any content may be never used it for auctions or commercial purposes, however feel free to post anything you see here with a courtesy link back, btw a link to the original post here , is mandatory.
All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Sunday, 16 February 2020

REPAIR / SERVICING TV LG 50LN5406 LED BACKLIGHT DEFECT - FLASHES SHORTLY TROUBLESHOOTING

The TV flashed the LG logo very briefly and then switched off again. The seller had a repair shop diagnose it and they said that the LED backlight was broken. Their repair offer was 320€. Wow. That's more than the used price of this device.
The LG of this age all die sooner or later due to one or more dead LEDs. The backlight in standard setup is too aggressively set up and they overheat.
I did not bother measuring anything and went straight on to a backlight repair.
Back cover off, nothing spectacular to see:

Step 1: Remove the front bezel:

Step 2: Unscrew the metal panel bezel, unplug the flat cables from the TCON board and carefully slide the buffer boards out of their seat:

Step 3: Remove the panel. This is the most delicate part of the operation. A 50 inch panel bends a lot when not handled correctly. I always wear gloves to avoid finger prints. Do not force a blade or similar objects between the panel and the frame to get a grip on the panel! A simple trick is to first unclip the black frame, raise it a little and then reach under the panel. That way it is easy to lift the panel with one arm diagonally supporting it from below and the other hand holding one edge to keep bending under control.

Be careful with stuck buffer boards. Make sure they slip out without force.

Step 4: Remove the panel frame and the foils. This is simple. Just wrap a tape around somewhere to keep them together.

Step 5: Remove the reflector sheet to get access to the strips. The four plastic standoffs come of easily when you squeeze them with pliers from the backside.

Okay. Measuring time! A good strip settles at 27.4 Volts. The bad strip yielded 36.1 Volts and it was obvious why. One LED was dead.

I removed the right half of the strip with a spatula, taking care of the double-sided adhesive tape, which will be reused.

Now, my new preheater got something to work on. The plan I had was to heat the strip up until the LED's solder would melt. Nope, not working. The material is too thick and a large copper trace shielded the heat from the top. Anyway, the lens came off very nicely under heat. The LED was so heavily damaged that it broke into crumbles. I removed what was left of it with the iron.

This looked terrible. The cathode pad was burned black all over. It almost seemed as if the soldering went wrong on this one and it heated up too much.

I cleaned it with a fiber glass pen and some Isopropanol:

This looked much better. Next time I will remove the sticker, too, before I work on the LED :-P

The SEOUL 2835 3V 1W fit perfectly. I put some leaded solder on the pads and the strip back on the heater. With just a short heat shot from the top with my heat gun at 260°C the LED snapped into place by itself on the molten solder.

The LG Innotek LEDs perform identically to the SEOUL, but some might feel more comfortable with the exact match.