Replacement Of Edge LED In Panasonic TH40C400D
This TV belongs to an ex-colleague and was brought to me with the complaint that the backlight was replaced by another technician, after which it worked only for a month. Once again there was sound but no display indication of a possible backlight failure. As I had mentioned earlier, I used to take extra loads to my techie friends and thus I took it with me to one of them who runs a shop in Chalakudy (19KM from my house), handling panel bonding, repair, replacement etc.
We opened the set and checked and found that the output voltage from the Inverter was present. When an LED checker was used also there was no response from the backlight. Now, this was a very complicated set, where everything has to be stripped from the backside, including a few rectangular brackets holding the panel. It took a lot of time to finally locate the edge led stuck to one side of the outer cover.
As it did not respond to direct check up at the connector points, my friend removed the strip and noticed that it was not properly fixed by the previous technician, as a result of which the connector had got loose from the strip. The Edge LED should be carefully laid on the side ensuring that the connector is free and in correct place. The sticking should start from the connector side to the last. Probably, due to lack of previous experience or presence of mind, the strip was stuck, straining the connector. My friend then checked the strip by giving voltages directly to the + / – markings. The strip was working, but not good enough as per his experience. So, due to making and breaking of the contacts, the LEDs would have got strained and the best decision was to replace it, which he did. Before replacing an Edge LED, for that matter, even the other backlight LEDs, the sticking area should be thoroughly cleaned and all residual gums should be essentially removed. This took a lot of time again, as he had to apply gum remover solution and rub every inch thoroughly clean.
Uneven surface might affect proper alignment of light to the splitter that redirects to the diffuser. Fitting of top sheets as well as panel might also be difficult and risky as panel is a very brittle part of the LED LCD TV. Anyhow after all these marathon works, he fixed the new LED carefully laying it beginning from the connector side. Later the top sheets and holding rectangular brackets were fixed with side screws and holding clamps. After this, the boards, T-Con and scalar board fixing brackets were fixed.
After proper reassembly, when the power was applied, the TV was found working perfectly well. After checking it for a couple of hours, the back cover was fixed. Here are a few pictures to view the inside and for the result.
Work completed to add satisfaction to the collection. TV was picked up from my home by the customer on the next and reported that it was working very well. He sent me a video too!
This article was prepared for you by Parasuraman Subramanian from India. He is 72 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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14 Comments
Leave a Reply
Tito Kanshulu
September 10, 2022 at 2:03 pm
Quite an educative article Mr Parasuraman.
Parasuraman S
September 10, 2022 at 10:29 pm
Many thanks for your comments!
Yogesh Panchal
September 10, 2022 at 3:09 pm
Good Fix, Sir.
Parasuraman S
September 10, 2022 at 10:29 pm
Many thanks for your comments!
Albert van Bemmelen
September 10, 2022 at 3:27 pm
Another very time consuming job professionally carried out! Sadly these led backlight strips cause us more time and trouble than the CFL-tubes ever did. Thanks for sharing.
Parasuraman S
September 10, 2022 at 10:29 pm
Very true! Many thanks for your comments!
Waleed Rishmawi
September 10, 2022 at 4:46 pm
good job on the repair. these LED strips in some TV sets are too complicated to be fixed. may times, I do not have the right LED strips so I take it to someone near by and he will do it for me. I used to do them past but not any more. thanks for sharing and have a blessed day
Parasuraman S
September 10, 2022 at 10:30 pm
Many thanks for your comments!
Imoudu.O
September 10, 2022 at 5:04 pm
Good repair work,I'm looking forward to when I will be able to remove panel successfully,at my first trial the panel got cracked though.
Sir, I have a crt tv which when I check B+ =114V, no joint wire non low resistor along B+ to collector of hot,so I remove bft and connect 100w bulb to ground and b+,bulb did not light and voltage is very low.Hot transistor o.k,I try your system for testing oscillation by use of red led bulb, it lit but flicking. Pls sir can you advise me what to do next. Thanks.
Parasuraman S
September 10, 2022 at 10:33 pm
Well it is a complicated process and cannot be responded here. I suggest you refer to all my CRT TV articles from the PDF file and help yourself. There are many reasons for no oscillation or flicker. We need to check it one by one. It again depends on the model and make.
Peter Sh
September 11, 2022 at 1:39 am
As always, a very interesting and informative article, thank you.
Parasuraman S
September 11, 2022 at 8:28 pm
Many thanks for your comments!
GIFT ELIJAH
September 14, 2022 at 10:50 pm
Good and detailed fix Thanks for sharing weldone Sir.
Parasuraman S
September 21, 2022 at 9:39 pm
Many thanks for your comments!