Philips 46PFL8007K/12 - Picuture flickers on half of the screen

[Capacitorial]

Hello guys.

I recently got a TV that has the following problems:

1. Sometimes it has to be turned on and off a few times, to boot up. Sometimes it starts from the first try
2. When it is running normally, the right side of the screen flickers. Sometimes it is just a square of transparent white maybe a 1/3 of the right half (top right)
3. The flicker is also sometimes a square that is filled with lines
4. I noticed that when the TV brightness is set to max, it flickers less. I think the Standard setting is the worst where it comes more frequent
5. When it runs a few minutes it gets better, but still presists and is bareable
6. The flicker you can see in the picture attached, is a pattern of lines and sometimes just those white 50% transparent short flashes

What I did is, I opened up the back and checked:

1. all ribbon cables and panel boards seem ok
2. Mainboard had no visual faults, the heat sink gets very warm though, I dont know if this is normal
3. The PSU seems ok, but there is a IC FSB127H (U501) with a diode (D501) nearby. The diode has continuity in both ways when unsoldered. I unsoldered it and it doesn't have continuity in both ways. Is that normal? The diode says T2D22.
4. The PCB around the diode has darkened a little but when running it doesn't get hot, neither does the IC.
5. The TCOM board (if it is a TCOM board) seems perfectly fine from visual inspection but it gets very warm.

I checked the schematic of the FSB127 IC, which seems to be a PWM controller of some sort. The pins 6-8 are connected to that diode which from there goes directly to the transformer. The transformer is between the hot and cold side while the IC is on the hot (high voltage) side.
I am at the beginning of my repair hobby. I can only guess that if that diode is faulty, that the PWM signal is getting messed up for that transformer that maybe drives a voltage for the mainboard and influences the picture quality or makes it flicker.

I do not know how to check the TCOM board for faults. I have read on the internet that others have similar issues, but they think it is not that diode because it is a two way diode? It was a french forum I had to translate, so not everything was understood.

At this point I don't know where to go from here. Can anyone help me out?

See attachments for further inspection
(IC Datasheet, pictures of everything)

[EazyBone]

There's a lot of info lol, I would look into your backlights.

[Capacitorial]

So, I guess this might be a dead end since I found other sources with the same and similar problem. This diode PROBABLY is a TVS diode. That is why when testing it in or out of the pcb, it will give different results.
I soldered the diode back in and will go on from here to check the ribbon cables that go from the TCON board to the screen.

[William1967]

The diode is not a TVS, the reason you measure a short circuit is because there is a transformer next to it whose coil you are measuring. The problem is in or around the processor.

[Capacitorial]

So I couldn't really find anything else. It seems that all the voltages are ok and since the TV is basically playing normally except for the sometimes flashing artefacts and lines, I guess it is a fault outside of the PSU.
The only thing I found was a ceramic capacitor on one of the panel buffer boards right under the panel, that was shorted. It beeped on both sides while all other capacitors didn't.

Is there a way to learn about those boards? I would like to better understand what they do and if a capacitor could be the problem for this faulty picture.

[nomoresonys]

If you're sure it's a cap and it's reading short, then yes that could be the problem, can you post a focused picture of this.

[Capacitorial]

Hello nomoresonys , this is the capacitor I was referring to. I cannot trace it to anywhere. The only thing I know is it belongs to CL1 which from what I have seen in videos can be a reason for this fault. The question is, how do I know how many µF it has to replace it?

EDIT:

I made a mistake. I desoldered the capacitor. It does not seem to be shorted. Doesn't beep on any side... The search goes on.
If I make the continuity check on the PCB where it was (on the pads of CL1), it still reads a short to ground. What does that mean?

[Diah]

short on COF or gate Transistor on LCD

[Capacitorial]

Since I know now that the CL1 capacitor is not short by itself (since I desoldered and tested it), how can I find where the short is? There are no tracks that I can follow. I turned the TV on without that capacitor and the fault was still there.

[EazyBone]

Don't think you can if it's inside the screen or cof. Looking like it's a goner

[lotas]

Measure the resistance of these test points relative to ground.

[Diah]

yours Photo, the trace line od the caps go to COF... try to disconnect VCOM12 line from the SMD R.

[nomoresonys]

Hello nomoresonys , this is the capacitor I was referring to. I cannot trace it to anywhere. The only thing I know is it belongs to CL1 which from what I have seen in videos can be a reason for this fault. The question is, how do I know how many µF it has to replace it?

EDIT:

I made a mistake. I desoldered the capacitor. It does not seem to be shorted. Doesn't beep on any side... The search goes on.
If I make the continuity check on the PCB where it was (on the pads of CL1), it still reads a short to ground. What does that mean?

Not exactly sure how you are measuring, I believe one side should go to ground that would beep but the other side should not, also just put both probes on the pads it came off of, is it still short?

[Capacitorial]

Hello lotas I measured the resistances you told me to check.
These 5.0-5.8MOhms resistances start rising to around 6 and go a little higher from there.
I don't really know what resistances to expect here, so I hope you guys can help me on that.

Diah, the cap you mentioned does not lead to that contact you marked. I checked with continuity mode and there was no connection. Actually, there is no component that connects to that point. I will skip this step for now, since there is no return after cutting it.

[lotas]

At the control point "L" SD 0.3Om is a short circuit, and it is the ceramic capacitor C"L"1 most likely located on this line, bus.

[Capacitorial]

At the control point "L" SD 0.3Om is a short circuit, and it is the ceramic capacitor C"L"1 most likely located on this line, bus.

Yes you are right, if I check with continuity mode the capacitor and the test-point LSD, it is beeping.
What makes me sceptical though, is that when I desoldered the capacitor and checked it with continuity mode, it did not beep.
Does this mean that the short is not the capacitor, but something AFTER the testpoint/capacitor? How can I check this?

[lotas]

Is there anything else connected to this buffer strip other than the panel? Is the T-CON disconnected from it?

[Capacitorial]

It is only connected to the TCON Board via ribbon cable. I disconnected the TCON board and the described shorts are still occuring. This time I used the ground of the board, not the TV chassi. So this means we can rule out the TCON board. The fault has to be on the buffer strip or the panel

[lotas]

Here you need to trace where this signal comes from the connector to the T-con and there are no more capacitors on this path, if there is nothing else, then try to very carefully cut this control point into two halves with a sharp scalpel, without damaging the adjacent tracks.

Post a photo of this bar in full, in good quality, maybe I’ll see what else I can check.

[Capacitorial]

lotas, I cut the LSD test point. All my testing was with the TV upside down, standing on the top edge of the screen. The fast flashing picture errors on the one half of the screen are almost never there. It very rarely appears for a split second. I turned the TV off and on again, and the picture was completely messed up. There was nothing recognizable. Then I turned the TV on and off again and now everything is good. Picture error very rare. Starts fast and picture is good quality and brightness. All perfect.

Now when I rebuild it and set it on its tv-stand, the picture error comes more often. It doesn't seem to a contact issue though, because when I touched and pulled on everything when the TV was open, nothing changed.
I will make multiple pictures of the board tomorrow, so it has more details. I thought that it fixed the issue and didnt make more pictures. The part we talked about is on the right end.