Revisit Of SONY KDL-43W800D For A Different Reason
This set had visited me in January, 2025 with a white display problem that got solved and perhaps those of you who have missed my earlier report can perhaps see the article using the following link:
https://jestineyong.com/intermittent-white-display-problem-solved-in-sony-led-tv-model-kdl-43w800d/
I had mentioned that I forgot to take a snap of the bypass 1.8V IC fixed in the TV and here is a chance for you to see it now:
The complaint this time (March, 2025) was ‘no display with 6 blinking codes.’ Six blinking codes in a Sony TV indicated backlight issues.
I opened the TV and checked the board. Let us have a look of the connected pictures before proceeding further.
The first picture is that of the power supply board which works from external 19.5V 5A Adaptor. The board has a regulator IC to feed 12V to the mother board. All secondary voltages required are generated in the MB. The second picture is that of the LED drive controller IC BD9397EFV. Third one is its application circuit. As you will notice, the IC has six driver outputs. We all know that electrons flow from the negative to the positive. In a battery, the electrons are generated by the negative potential and positive collect it as and when received through the load. The speed at which it flows is current and it depends on the load. Why all these now?
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Just for the beginners to understand the function of this driver IC. I saw the required voltage build up (around 42 Volts.) The electron generation at pins 11 to 16 for handling six arrays of LEDs as can be seen in the second picture above, was just starting and stopping. It indicated a failure of the back light LEDs. So, started dismantling of the TV as we need to remove the panel, the diffusor and reflector sheets to locate the backlight.
The third picture above is after removing the two strips of Edge Led strips stuck at the bottom side plate. These are connected by strips. There were 42 LEDs, with three arrays of 14 LEDs in each in a strip. The length of the strip was 43cms. Let us have closer look of these and the connectors:
I could not check the LEDs without seeing the connectors at the LED side. There were two + and three – markings on the connectors. This meant that positive connection was commonly given with three separate negative connections to each array of 14 LEDs linked in series. So totally six connections from both the strips were driven by the IC outputs.
I happened to see one LED with a slight burning mark, the cause of which could be one dead insect stuck to the strip in the same area. How it managed to get in there baffled me! Let us have a look of it and that of the connectors:
Both the strips were tested and found to be defective. As these LEDs were not locally available, I placed order and got the same after two days. But the connector was slightly different. The original had ten pins with the first one blank, the next two + marked, the next pin blank, the next three pins – marked and last three pins blank. But what I got was this:
Perhaps you would notice from the first picture that there were two blanks between the + and – marks. So I provided a jumper wire in the PS board, which can be seen in the next two pictures given above. I also cut the pins which can be seen from the third picture to prevent pulses going into the LED strip through that. Then applied power to check whether it was working, keeping the strips without fixing it. I allowed it to run for an hour in this condition:
After ensuring that the new strips were ok, I fixed both the left and right strips in its place. Then fixed the panel back with its metal frames. When I applied power, the backlight was ok, but there was no display. I looked for any problem in the T-con board, as it had undergone a bypass last time. The voltages such as VGH, VGL, V-com, AVDD etc. were ok on switch on. Then I tried removing the LVDS cable one by one to check whether one side at-least showed up. It did not, indicating that the panel had internal defects. On consultation with my techie friends, they said that the panel was faulty and required replacement. I checked with my friend who handled panel replacement and bonding works and he gave me an estimate. I communicated with the customer and sought whether he was willing to go for a replacement.
Since he answered in the affirmative and wanted only a few weeks to arrange the funds, I kept the case aside until he made the full cost as advance.
I took the TV to my friend’s place which was around 30KMs away from my home and he carried the TV from my car to the first floor without letting me do it (a milk of human kindness!) as the TV was of metal frame and very heavy. I had to wait there as his place was always thronged with technicians. TV got ready after waiting for about 5 hours. When the TV was checked for correct functioning, the backlight was found flickering. As he had no time to re-open the back cover, I left it there and returned home. He reported later that the driver IC was getting very hot and needed replacement. I gave him full freedom to do whatever he deemed necessary to ensure that the TV was back to perfect working condition. He took the board along with many others of his own to a place around 250Kms away, where he visited every Thursday. He always combined his visit not only to get defective boards repaired, but also to pick up spares and panels to replenish his stock. I visited him after a few days when he gave me the green signal to come. He fixed the back cover in front of me after showing the replacement of the IC and switched on the TV. It was working fine.
I carried it back home. The TV was delivered after two days’ trial in my home. The customer reported that the TV was flickering again the next day. Then I went to his house myself in my car and checked and found out that the backlight had failed again. I checked the power connections and found it to be ok. The customer himself was an electrician and had maintained it very well. I brought the TV again for a check-up. The backlight drive was intermittent and dropping.
I tried joining all the six outputs as this is a trick generally used to balance the current and then I cut off the fail output from pin 2 of the IC to the Main Board.
Those of you, who are interested in studying more about the feedback circuit, may perhaps read my article, where I have explained it in detail. The only difference in that IC was the clock pulse interactions with the Mother Board:
We should remember that six arrays of 14 LEDs in each are connected in parallel to the IC, which in fact draws more current. I combed the inverter area for any change of value of components, partial short of caps or track cuts etc. and could not find any. After doing these trouble shooting methods and remedies employed, the backlight got on when I switched on the TV. It worked for a couple of hours and started occasional flickering. That’s when I thought of providing an external LED driver board instead of wasting time on trying to rectify a defect, reasons for which remain obscure. Let us remember that the IC was replaced by my friend earlier. I picked up one of the Universal LED driver boards which has a reference number of Gold-08ES with multiple connectors. Let us have a look at it:
This board safely works from input of 12 V to 26V. As the DC power supply available in this TV was 19.5V, it was safe enough. The LED Driver board gave an output up to 180V. The only question was whether the board will take the load.
The six sets of LEDs are wired in parallel as already mentioned by me which will draw more current. First of all, I cut the tracks of + and – in the PS board near the LED strip connectors and made it completely isolated. Then connected two wires, one for positive and another for negative supply inputs for the board. In order to cut short the current drawn, I wired both the LED strips in series by wiring the output of one LED connector on the PS board to another, which meant 14 LEDs (three parallel connections: 42nos of LEDs divided by 3) in each strip. That made a total of 28 LEDs in two strips drawing 84V @ 3V per LED. Then the already joined six outputs were cut in the middle to make it three each on one side (Please see picture one below). I kept the PS and driver boards side by side and wired them appropriately and applied power to check the voltage and ampere readings:
In order to save you from eye strain, let me mention that the voltage was 79.9 and current drawn was 202mA. The mother board was not connected at this stage and I had connected a 10K resistor from the DC input to the Power On pin in the LED driver board to enable auto switch on. I allowed it to remain on for an hour, during the time of which I checked whether the driver Mosfet was getting hot. It remained cool and that cooled off my brain too by easing out tension!
The next step was to connect the mother board and check whether the 19.5V dropped. The input voltage was steady and the backlight got on immeditely when we powered the TV because of the auto mode modification done. I could have provided the control of it from the mother board, as the driver IC was getting an enable voltage. But I did not want to disturb any of the original wiring there as Sony has a lot of interactive sessions and the motherboard would detect some ‘suspicious activities’ and shut down! The disadvantage is that the backlight would remain lit the moment the TV is powered! Anyhow, the backlight issue that looked like a perennial problem was solved. Then I fixed the Inverter board besides the PS board, where there was adequate space. The TV was tested for three days by switching it on for at-least 12 to 18 hours a day. The TV was picked up by the customer and I regularly followed up and learnt that it was working very well. (TV came in in March and given out in July!) The customer was very nice, endurant and understanding and paid me very well covering all the costs incurred by me and I took only a nominal profit margin as a reciprocal gesture!
Such customers are very rare to find now-a-days! Mission accomplished with greater satisfaction getting collected!
This article was prepared for you by Parasuraman Subramanian from India. He is 76 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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Albert van Bemmelen
February 28, 2026 at 7:01 pm
Seems to me that Sony and in particular this tv was a big pain in the -you know what- Lol!
In such cases it maybe is a very good idea for any customer to buy a Magcubic HY300 Pro+ 8K Android 14 Portable Projector 8000 Lumens with WiFi 6 and BT5.4 Outdoor Theater 5W HiFi Speaker that supports 720P and HD resolution as TV replacement device instead?
When it projects 8K video on any wall in the living or bedroom, like for instance an Android outside view of a window video showing a fantastic 'life-like' looking out a window into a city, it will look your home has windows where there are none!
Parasuraman S
February 28, 2026 at 7:55 pm
Many thanks for your expert comments and very useful tips and suggestions. This customer was adamant to have the same TV back in working condition for reasons known to himself.
Albert van Bemmelen
March 2, 2026 at 12:56 am
To show why I mentioned the MagCubic TV projector here a short demo videoclip I saw on FB recently, the 'life' window video demo is magical! See: https://www.facebook.com/reel/1638164644291110
Parasuraman S
March 2, 2026 at 12:27 pm
Unfortunately, I have exit out of Facebook and deleted all my accounts long back. Many thanks.
Mark J
March 1, 2026 at 4:04 am
Parasuraman great job on the repair very thorough. I always enjoy your articles.
Parasuraman S
March 1, 2026 at 8:34 am
Many thanks, dear Mark!
MP
March 1, 2026 at 6:32 pm
Thanks Engineer Parasuraman. I need another 3 days to read the article more slowly and gain some skills. Later I will be periodically revisiting the 2 articles. It cant be done in one go, no, certainly not.
Parasuraman S
March 1, 2026 at 11:42 pm
Many thanks for your comments! Please take your time!
Yogesh Panchal
March 4, 2026 at 4:01 pm
Good Job! Sir,
Most of the time Bypassing BD9397 pin no.31(CP) using 10k Resistor to Ground solve the problem.but in this case IC was overheating,indicates shorting of the IC Internally.there was time in CRT TV where some common IC & Transistors used & we can stock it but now it is very difficult to stock the material because of continuous technology change.
Parasuraman S
March 5, 2026 at 8:28 am
Yes, there are millions of parts which keep changing from model to model and sometimes between same models too! Manufacturers discourage service and a prolonged life for their products, and this is one way of keeping us, technicians, at bay! Many thanks for your comments, dear Yogesh Bai!