Repair of Philips LED Smart TV – 55PFT6100/98
I had received a Philips LED TV from a friend. It came with the problem of, no picture but with sound.
Before dismantling the TV to confirm the failure, I powered up the TV to see myself the actual fault. Indeed, there is picture and sound but picture was not visible due to no backlight. You have to look closely or shine a torchlight to see the picture in the display panel. This confirmed that the supply is going into the Mainboard, T-con and LED Panel. Next, I had confirmed whether the mainboard sent back blacklight ON signal to Power Supply Unit (PSU). For this I needed to dismantle the cover to find out.
Picture of back cover dismantled
Power Supply Board (PSU) connecting to the mainboard
Checking that the signal from the mainboard to the PSU at CN203 after switching on the TV at BL_ON. The signal or 4.3Vdc was present.
This test confirmed that the mainboard is working and the next step is to confirm whether there is output to the LED strips from the PSU.
There are 2 pairs (CN301) of LED strips – LED1+ and LED2+. The first (LED1+) was tested to have 130 Vdc and second (LED2+) was receiving 113 Vdc from the PSU.
These results indicated that one set of LED lights having higher voltage that the other implying that there could be a fault in the LED strips.The final test was to conclude which LED strip is causing the TV to have no backlight by using the backlight light tester (SFD300V).
After removing the connector going out from CN301 to the LED strip, using the backlight tester with TV power in OFF condition, the first set (LED1+) failed to start the LED but the second set (LED2+) started to light up slowly. This test confirmed that the first set LED1+ is causing the TV to have no backlight. Now to dismantle the LED TV glass panel from the chassis.
Removing the LED TV glass panel is difficult. One has to take precaution not to break the glass, once cracks appears, the TV will be unusable. Once the back chassis has been removed there were 12 strips of LED divided into 2 sets. LED’s connected to LED1+ had 2 LED’s not lighted up when using the LED backlight tester checking each strip at a time. Replacement strip took 1 week plus to arrive from AliExpress.
LED1+ after replacement was made
TV back to life after assembled.
It was an experience to give life to this TV and begin the first time for me the satisfaction of completing the task was just great.
For this TV repair I had my son Shawn to assist and somehow this session got him hooked on and now he is keen on taking up electronic course where I attain my basic knowledge, it’s from our one and only, Jestine Yong, KL Malaysia. Thank You Jestine Yong.
This article was prepared for you by Michael Selvam from Singapore, a 57 year old zealous electronic enthusiast. As a passionate electronic repair hobbyist, he tinkers with home entertainment systems and any faulty electronic equipment he gets his hands on. He obtained his knowledge to repair by reading books and took up the electronic courses I conducted. At present, he is employed as a Cluster Manager (Property Management) with CapitaLand and does his repair whenever time permits.
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