Philips 47PFL4606H/12 flickering issue/strobo effect

[tuner2000i]

hello everyone!
I am new to this forum. I joined in order to search help for an issue i am facing with a personal TV. I am not new to electronic repairs, but i am not very familiar with tv stations. i do mostly smd rework and playstation repairs.

This Tv I bought a few years ago, a philips 47PFL4606H/12. i purchased the TV as faulty, the antena receiver was not working properly, the image had noise because the antenna was broken and poorly repaired. i bought another motherboard quite cheap, which i used until today.
The problem is that the backlight started to make strobo effect. Initially this happened when i started the TV, and dissapeared after it warmed up. then it started doing it most of the time. i took it apart thinking that the caps from the invertor board might be bad. but this tv has the invertor on the power supply board and all the caps looked fine. I put it back together and updated the system software. It worked great for about a month, then stated doing it again. Meanwhile i repaired the original mother board antenna receiver so i took it apart again today because i could not use it like that anymore and put the original motherboard back in while cleaning and inspecting the power supply again. now seems that its working again, but i did notice the flicker two times for 2-3 seconds.
Sometimes the flicker appears when changing the input, but it does appear on all inputs i tried (2 hdmi and antenna).
I am almost sure that the issue is backlight related, but i dont know what to do to fix it. since its not doing all the time, its hard to figure it out. i noticed that the more i keep it plugged in (turned on or off does not matter) the more often and longer the ficker occurs.

here is a video with the same model of tv and same issue i found online
another video, same problem, same model
I also attached some pictures of the power supply board. i would start by replacing the big capacitor 450v 120uF but again, i am not a tv techician. so please if you have any advice let me know.

Also the power supply is making a buzz noise ever since i start the TV. It has been like this since i bought it. i am not sure if this is normall or not. You can only hear it if you are close to it or if it's silence in the room

EDIT: i found this video claiming that the problem was from the screen connectors if i understand right. they are not exposed and i do not speak russian. do you guys think i should take it appart and inspect the issue?

[Moreno83]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

You probably have failing backlight. ( CCFL tubes ).

This is due to aging. The tubes are getting older and in the end its demanding more power from the supply which it cant deliver , thats why its flickering.
You could try to check the powersupply and see if it needs resoldering on the transformer. Bad capacitors are not really a issue nowaways , it was with the older samsung lcd's.

On the earlier ambilight models the blue ceramic caps near the trafo blew up stopping the tv from turning on. I think these 2 caps are there to prefent overcurrent because the ccfl tubes are demanding more power.
I think you can remove them and it will probably "fix" your issue but i need a expert to confirm that....

It is basically the same as the tubes you see in old sheds. They blink a few times before turning on or blink ocassionally and have black spots near the 2 ends.

So besides checking the solder there is not much you can do unless you have acces to CCFL tubes.


http://backlightweb.co.uk/index.php?..._image&pID=541 <- this is what you need.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

thank you for your reply. i was thinking as well that the ccfl tubes might be dying, but since the flicker is equal from both sides, i thought that it can not be such a big coincidence that both are dying in the same time. that is why i started thinking about the power supply. but what you are saying could make sense as well. i am not an expert either.
if that is the case i would replace the tubes but i do not know where to buy them from. I really want to repair this tv. it might be an old tv, but i love the image quality on it.

meantime, i opened it again to check the ribbons the russian guy showed in his video. mine did not have any holes in them so i think the problem is not from there. they were however not sitting straight at all (see pictures). I took them out, properly cleaned them with IPA, put them back on and taped them straight and nice.
The tv is running for about 3 hours, no flicker until now... but last time i opened it there was no flicker for about 1 month, but once it starts then i have it eveytime i turn on the tv. i dont see any connection here...

but i would replace the ccfl tubes anyway.

edit: i just looked at some pictures online and saw that the ccfl tubes are positioned horizontaly and not vertically as i thought. its same as in Led tv's just that its ccfl tubes. and its more then 2 as i thought, so it looks like i need a whole kit.

[Moreno83]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

The tubes are as wide as the LCD is. So that's why you see it on the left and right side.

EDIT: I see you changed your post.

Yes LED tv's also have leds positioned over the whole screen. Makes sense as the whole screen needs to be filled with light haha.
You dont really need a whole pack but it is wise to order a full pack OR search for the same model ( 47 inch LCD tv ) with defective panel.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

yes, i have repaired a led tv before. an LG which i also bought as faulty and the leds seem to die one by one.
I would rather buy the ccfl tubes new then from a used tv. no matter if the screen is faulty or cracked. they can still have some hours behind them. this tv does not have many hours since i have it, but i dont know from before.
still, it does not mean that the issue is from there.
i assume that ccfl tubes should be quite universal, but is there any way to find the length i need without opening the TV? i saw that i can buy them from aliexpress

[Moreno83]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

These tv's give indeed a nice picture.
Did you check the powersupply for bad solder on the transformer? You could lower the backlight itself in the menu.
If that does not work you need replacement CCFL. They sell it as "CCFL 1075 mm or 1077 mm".


https://www.lcd-chip.com/ViewDetails12277.aspx


If you cant find the replacement CCFL you can try to remove the blue caps as last option.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

i tried searching locally for the ccfl tubes and/or power supply.
i could not find any. I did not open the tv since my previous posts. will do that in the following days. any advice until then is highly appreciated


here is a video made by me, where you can see exactly the problem

service manual on page 59 there is a diagram of the invertor circuit. i can see there is an invertor controller ic there (i saw it on the power supply board as well). can these go bad?

edit: the capacitors that you mentioned removing, are the ones in the picture below? C905 and C906, can be seen in the diagram on page 58

i do a lot of playstation repairs and iphones, but mostly smd and bga rework. so i work mostly with DC voltage. in the video you can see at the end there is a constant sound coming from the transformer i believe, when the flickering appears the sound is doing the same as the flicker (it's almost like the sound is flickering as well). i am not sure if this sound is normal or not but it was present ever since i bought the tv.

also there is another issue i forgot to mention. ever since i had the tv i think it happened about 10 times until now, when i started the TV, the image had lines and ghosting, and this sound i mentioed, if i rememer right it was stronger in that point. all i had to do is turn off the tv and turn it back on and it was good. sometimes even waiting a few seconds made it go away. i attached an image from the internet similar with what i had. i think this should normally be from the t-con board? but i think this tv does not have a t-con board. so maybe again something from the PSU?

[budm]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

Just curious, if look at the LCD panel on the back side holes, do see flickering lights?
To me it looking like the video flickering not the backlights due to failing panel.

https://www.badcaps.net/forum/attach...8&d=1528759630
That is LCD panel problem, Gate tab bond failure.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

Yes, i can 100% see the backlight flicker. That issue happened as i said 10 times in 300 starts lets say, and maybe it was caused by the ribbon connectors. As you can see in the pictures above they were not actually sitting properly. I think the sound i am hearing is coming from the invertor itself. I remember hearing this when fixing an old laptop, coming stright out of the invertor

Ps: after i made the video i left it on for a few more hours and the flicker never came back again. Right now, on cold start it took about 10 min to come, and its gone again, but it was enough to make sure that the light in the back is flickering as well

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

looking at the manual you posted i think i had more like a GATE DRIVER FAILURE then gate tab bond failure. but this thing happened so rarely and lasted so little that i am not able to make a picture. i did not see this thing for months

[budm]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

You are getting multiple images.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

that picture is from the internet. i just said i had something a little similar, but i did not get double image. my problem is not the panel, it is 100% something related to the backlight or power supply. i can see the backlight flickering in the back of the TV

also one thing i noticed that can be seen in the video as well, the flicker never appears until the TV fully loads. for example while displaying the philips logo there is never flicker there. only once the tv is fully booted i can see the flicker. it's like when the tv is loaded it consumes more power and then i can see the backlight dim a little and sometimes start to flicker right away.


i found this video online almost same flicker on a vizio tv was caused by bad caps. but in the video its very obvious they are blown. mine look intact..

[budm]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

What happen if you turn down the backlights level?
What PFC boosted DC Voltage do you get by measuring right between the two legs of the 450VDC main filter cap? This flickering reminds me of the Samsung with flickering backlights due to low PFC Voltage.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

i dont think this TV has a backlight adjustment setting, but i will check again to make sure. i know 100% that dynamic backlight is turned off.
also, tomorrow i will open the unit and measure the voltage and check for cold solder joints.

thank you for all the help! do you think i should try removing the two capacitors mentioned above?

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

i have 371 VDC between the legs of the 450VDC capacitor. Also i can 100% confirm that the backlight is flickering as i can see it when i take the cover off. also the constant sound i am hearing is coming direcly from the inverter.

is the voltage right? because i can not find anywhere the value it's supposed to have.
i put the original motherboard inside and it says the TV has 1130 hours

also as i mentioned the flicker never appears while the tv is loading and displays the philips logo. also in this time i noticed there is no buzzing sound coming from the invertor. i only use this tv in the weekends, so it can not have many hours on the new motherboard either. i would say a total of 1500 hours. i also remade the soldering under the transformer and invertor, though it does not look like any of them was cold or not done right.

[budm]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

The Boosted Voltage typical value is between 380 ~ 400V DC. Your schematic shows 395V on page 59 (EN 59).
In Samsung, 360V and below will trip under Voltage shutdown, but I do not know if Philips has that protection circuit or not, so far it does not look like it has UV detection.
1130 Hours is very low for TV.
I sure hate to open the panel to find out that the lamps are OK.
Did you verify that all the board mounting screws are tight? They use that for GND connection to the chassis and between the boards.
You have power supply/inverter board combo, so is there another board that the two HIGH Voltage wires from the power supply go to?
May be you should up load the pictures of the whole back side of the TV showing all the board.
What is the LCD panel model number?

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

thanks for responding so fast.
all screws are tight 100%. i am not sure if there is another board where the high voltage wires go to, but there are 2 connectors, so maybe there is??
the display is an LG LC470WUH

[budm]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

The connector on that power supply board that goes to the main board, it has pin name for each pin but I cannot see them using your pictures.
Can you please provide us the pin names for those pin?
I wonder if the Dim control pin Voltage is not stable.

[tuner2000i]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

you have a point there. just checked and remade the soldering on the PSU for pin 1 and 2. also on the motherboard connector pin 1 looked like it was not perfectly making contact. i took both pin 1 and 2 out of the plug and made sure that they are tight.

on pin 1 i have 4.95V
pin 2 has 2.63V

no fluctuations... I put all back together hoping the issue was fixed, the buzzing from the invertor seemed more constant but then i still got some flicker again.

i also tried messing with picture setting on the tv. power saving preset did not do much, the flicker seemed even stronger. only "picture" preset seemed to reduce the flicker. anyway changing between them seemed to stop the flicker for a while then start again in 1-2 seconds.

EDIT: seems like the buzzing sound from the inverter is GONE! the buzzing sound i am hearing now (the constant one) is from the motherboard, from under the heat shield when the "no signal" is displayed on the screen. if i try switching the channels i have no sound at all.(i have no inputs connected at this time) this is definately a new one

EDIT2: i turned off the tv and turned it back on and the buzzing in the inverter has come back and it's covering the one from the motherboard. also i tried turning on with only 1 high voltage cable connected to the inverter and the buzzing was even more louder, annoying actually. maybe the inverter is the problem? also the flicker was back, even stronger with only 1 high voltage cable connected. during this time, voltage on pin 1 and 2 were the same, constant, no fluctuations

[budm]

Re: Philips 47PFL4606H/12 flickering issue/strobo effect

Pin 2 is the backlights level adjust that control how hard the lamps are driven, if that control Voltage fluctuates then you will see the backlights not on steady, but you indicated that it is steady.
If you remove that wire to pin 2, the backlights will be on full.