Backlight Issue And Jumping Image Problems Resolved In PHILIPS 43PUT6002/56 LED TV
This TV belonged to a relative of my colleague working in the hospital. The complaint was no display. On checking, I found that the TV came on with a flash of the backlight, but it went off immediately. After opening and cleaning the set thoroughly, I checked the LED driver output and found it to be normal. The checker showed zero consumption when backlight connection was removed and checked. It indicated a failure of the backlight.
So, disassembled the TV step by step; disconnected the LVDS cables that went to the T-Con board, Freed the scaler boards from its hold on the frame, removed the panel holding frame from the front and gently removed the panel and shifted it to one of the vacant beds in yet another bedroom of my house. Then removed the polarizer sheets and reflector sheet. The following pictures would enable easy understanding of these descriptions:
When I removed the inter connectors and checked each strip using the LED backlight tester, all of them were found working. So, it was a case of overdrawn current by the failing LEDs. As mentioned by me earlier in several articles, never ever try to replace a portion of the backlight under any circumstances as there would be a mismatch of current drawn and the old LED strips would fail soon, sometimes even spoiling the new ones. Bought 8 strips and replaced the old ones. I noticed that the connectors were flimsy and therefore went ahead and soldered the wires directly on the strips. Two sets of four each were connected in series on both left and right sides. As you might observe, the lights are fixed from top to bottom, instead of left to right usually found. Each strips had three LEDs, which showed a consumption of 16.7V indicating that the LEDs are that of 6 Volts. Fixing of new strips were done after thoroughly cleaning the base and removing the residual gums, in order to ensure proper dissipation of heat generated by the LEDs. Tested the LEDs by directly connecting it to the board and powering on the TV. The LEDs lit brightly.
The story took a twist when I reassembled the TV and switched on. Just look at what I saw:
There were horizontal lines on the screen. The thick line you see at the bottom is not a defect but is a progressing bar while the software is loaded and made ready and is an indicative part of the start-up process. Apart from this problem, the display was jumping and freezing, which I could not capture directly and I played the video in pause mode and selected a suitable still from it:
As usual, I published in my Whatsup group and sought solutions. I was surprised by the feedback that the 43” LG panel had developed such problems in almost all the TVs. Looked like it was a manufacturing or design failure. As a crude solution, I was advised to cut the tracks of ODD and EVEN outputs of the following IC, and give VGH and VGL voltages respectively to EVEN and ODD tracks that go to the panel.
I traced the tracks by analogue Multimeter (Of-course, the TV was disconnected from power), turning it to X1 range, and connecting the probes between ODD and EVEN written near the connectors that go to the panel. The tracks were directly going to pin 54 (EVEN) and 55 (ODD) of IC No SM4080A. Strangely, the pin numbers were itself even and odd numbers! Following pictures would enable better understanding:
I cut the tracks that come from the IC near the two through-hole joints you see on the left picture above. We have to remember that since the T-con board has two outputs these ODD and EVEN are fed to both sides and they therefore are interconnected from one connector to the other internally in this multilayer board. Then located the VGH and VGL points on the T-Con board and used two thin jumper wires to feed VGH to EVEN and VGL to ODD tracks that go to the panel. Unfortunately, I forgot to click the connection in my anxiety to see the results. The TV worked normally without any jumping, though the horizontal lines were still there.
What did we do here technically? The symptoms showed that components in the corresponding tracks were shorting inside the panel and the horizontal lines were result of burning of crystals due to such shorts. The freezing and jumping was taking place either on ODD or EVEN lines inside the panel. What we did was feeding permanent plus and minus voltages to the panel on those defective lines and making it inactive to prevent interference. In a sense, a type of quarantine!
Anyhow, the TV was back to working condition and I delivered it to the customer with due explanations of the faults. He was aware of these problems, but forgot to mention it and was happy that it could be solved. He was going for a new TV and was ok with this temporary fix. Satisfaction with intensity jumped into the bag, pulling the curtain down on this story.
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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You may check on his previous article on Revisit Of Toshiba LED TV Model 32PU200E1 After Three Years