Four Different Cases Of Backlight Issues
As mentioned by me before in a few articles, these are cases which I attended to in my friends’ shop. I am sharing this with brief description and pictures for those who are interested in knowing the issues, resolutions and also to have view of the inside of the sets.
Case 1:- Make: Haier – Model: LE32M600C – Complaint: Low glow at bottom
After opening the set and checking the backlight with an LED tester and also the output of the LED driver on the board, it was confirmed that the issue was with the backlight. So, removed the panel and replaced the backlight.
After replacing the backlights, the issue was resolved, as you can see from the following picture:
Case 2:- Make: Panasonic – Model: TH-24C400DX – Complaint: No backlight
In this case, it was detected that the LED Driver was defective, as the backlight was ok when checked with the backlight tester. As it was a combo board, the best solution was to provide an LED inverter board. The 12V supply and ground was tapped from the combo board.
The power on was taken from pin 10 of the inverter IC. This universal LED Inverter board had multiple connections in the output and the appropriate output suitable was selected. Just see the connections:
After checking all work done, when the set was switched on, it worked perfectly well:
Case 3: Make: Videocon – Model : LWDTWKC40FH-ZMA – Complaint: No backlight
After doing the preliminary checks of backlight with the LED checker, the focus was turned on to the inverter board. Indeed a completely dry soldered transformer was found.
After cleaning the area very well, fresh solder was applied and when the TV was tested, it worked very well:
Case 4:- Make: Videocon – Model : V3218LEDTV – Complaint : Blinking backlight
This Videocon TV belonged to my colleague in the Hospital, and was the one in which the panel was changed. Subsequently, it developed a problem with the backlight and the Mosfet was changed by my friend, as the panel change work was done in his shop.
Again it came to his shop, as per my directions and when I opened the set; I noticed that the LED driver itself was having a problem. It was switching on and off. Instead of wasting time on troubleshooting the board (as per his shop policy), an LED driver board was fixed on top of the heat zinc using the screw of the Mosfet as fastener.
The 12V supply, ground and power on was taken from the board.
The TV was found working very well after doing this bypass surgery!
Thus missions accomplished and satisfactions got collected!
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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