Philips Pus 436401/12 flashing backlights question

[KevM]

hi had loads of help from this forum getting TVs back up and running but seem to be hitting a brick wall with this one.
Backlights failed before Xmas so ordered a new set and after replacing them and putting the set back together was delighted to see it work for 15 seconds only for the picture to flash on and off and a quick look round the back confirmed the backlights were flashing on and off

I have a steady 44v at +vled and a fluctuating 0v to 10v at -vled when the light start flashing, a steady Bl-on voltage and steady dim voltage.
If i disconnect 2 strings of leds the light stay on which leads me to believe an overcurrent problem.
I have now found a website that suggests increasing the rating of the 2 current sensor resistors which i believe are rated at .33ohms.and is a particular problem for this 715G6973 board.
My question is if anyone has come across a similar problem and done the same modification then by how much did they increase the resistor by

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

If i disconnect 2 strings of leds the light stay on which leads me to believe an overcurrent problem.

NO .. you have 2 group of VLED+ . the one you disconnected mean you install the strings of this group in wrong way or one or more LED failed. . .. it should always at strings the VLED+ goes to the first LED+ and at the end of the strings which will be - should go to next strings first LED+ and so on if the backlight are direct LED.

always philips can turn on and BL come on with out screen. so you will be able to see before you put every things together.

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

Hi i do not have the screen in place at this time i understand the lights will come on without the screen in place. The leds are brand new.

there are 5 led strips of 12 on each strip all supplied from the same connector it does not matter which 2 strips I disconnect leaving 3 connected the lights stay on. which proves to me the leds are not the problem.

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

how many cable you have on the PCB socket of BL ?
and how many cable on each strings socket 3??
how it come 43 size have 5x12 60 LED..??? 55 size have 54 led !!!!

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

i have attached photos so you can see for yourself . i did not design the tv so cannot comment on why so many leds on each strip. i have replaced several led strips over the last year and never had any problem like this one.

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

take it easy.... i dont doubt yours know how ....this is diy work not original and you are following DIY not original.. it so far from original design. end. show yours strings... why you hide them. you have now one channel cancled... the original have 2 channel LED--- see you have 2 big filter caps.

this will be my last post on this forum good i reached 3000 and didn't got brain shock. stay healthy all.

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

i have attached photos so you can see for yourself . i did not design the tv so cannot comment on why so many leds on each strip. i have replaced several led strips over the last year and never had any problem like this one.

why you don't answer my questions ? where are the original design you talking about ? if you were tricked by some seller don't transfer the tricked over here... if you want to bring it to original just say( sorry i did mistake ) we will help you immediately unless yours UK nose so high.

[R_J]

Re: Philips Pus 436401/12 flashing backlights question

What is the voltage across the main filter cap, C9109? If you can check this voltage in standby and when the power is ON. This is to check that the pfc circuit is working.

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

What is the voltage across the main filter cap, C9109? If you can check this voltage in standby and when the power is ON. This is to check that the pfc circuit is working.

sorry.. WATF*** are you talking on here... i think you are mixing with other threat,,, he had DIY BL 1 2

[R_J]

Re: Philips Pus 436401/12 flashing backlights question

sorry.. WATF*** are you talking on here... i think you are mixing with other threat,,, he had DIY BL 1 2

The question was for the original poster. What is your problem?

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

Hi reply to Diah , in post 6 you said this is my last post on this forum so i did not make any response to that post . I have only just realized the wrong picture was uploaded in my reply to you.
as an update over the weekend i replaced the 2 resistors pictured in post 1 which gave a 1.1ohm ,resistance the backlights came on but less bright { as expected} but took longer to start the on off flickering. i have attached a picture of what i think you are requesting of the string connections if this is not the case then sorry. I checked the backlight wires for continuity and all are ok.
If i can be clear that i do not intend to upset anyone on here i try to make replies concise and clear. if the post regarding large caps voltage was intended for this thread then the volts are 390V. when switched on and only move by a volt or two when backlights flicker.

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

The manual for this set is found by chassis code and the chassis is QM 16.3 and covers a whole range of philips power boards and different power units and not the easiest of manuals to navigate.
the backlights for my set are part number GJ-2K16-430-D512-V4-1 and the only difference between original and the replacement is the new parts come in 2 pieces whereas the original are one long strip . Would this make a difference?

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

Hi reply to Diah , in post 6 you said this is my last post on this forum so i did not make any response to that post . I have only just realized the wrong picture was uploaded in my reply to you.
as an update over the weekend i replaced the 2 resistors pictured in post 1 which gave a 1.1ohm ,resistance the backlights came on but less bright { as expected} but took longer to start the on off flickering. i have attached a picture of what i think you are requesting of the string connections if this is not the case then sorry. I checked the backlight wires for continuity and all are ok.
If i can be clear that i do not intend to upset anyone on here i try to make replies concise and clear. if the post regarding large caps voltage was intended for this thread then the volts are 390V. when switched on and only move by a volt or two when backlights flicker.

2 filter caps mean of the BL circuit.. see picture so you have 2 channel. each channel supply same currents over all TV brands. you have at each channel 3 LED- before i go further.. can you show me the back side of the socket circuit.. this configuration you show at socket wire make no sense so let see the back side first.

[R_J]

Re: Philips Pus 436401/12 flashing backlights question

KevM, I have seen other threads where the main voltage was low and the backlight circuit was not getting enough voltage to always stay on. I thought in this case since your backlights would operate with 2 strips and not all of them this might be something to check.
Your pfc voltage is ok so this would not be the problem in your case.

I hope you get it solved soon. Sorry for any misunderstanding

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

R J No problem

i have enclosed pic of rear of circuit board and connector.
please let me know if this is what you want to see.
I understand the part about 2 channels of supply to the connector.

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

i have enclosed pic of rear of circuit board and connector.
please let me know if this is what you want to see.
I understand the part about 2 channels of supply to the connector.

sorry i was wrong because the print chart of the BL socket on top side absolutely wrong ,, and you have just One channel as LED+ pin 1.2 are connected to LED+ 11.12 and all LED- are one pin connection too.

you said the measurements on LED+ was 44.V. so do you still have the Old original strips. to test one LED only if it had or not zener diode built in at reserve probe. ?

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

Yes i still have the old strips but they don't have a protection Zener diode on them .
I take it you mean something like in the photo i attached of some Samsung strips. I have only ever come across a Toshiba set that had a shorted diode on the strip
Manual states a boost voltage of 48v for this power supply but i have only ever got 44v
when i switch on and stays steady.
Could one of the TPV101D ICs be faulty and breaking down so only one is taking most of the current and going into shutdown ?

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

44V this is voltage but how about the currents.. here you have lack with it so couldn't support all 5 strips. do you have the S,M of the PCB ? if not upload closed photo of back side of this photo part to follow up the chart-

[KevM]

Re: Philips Pus 436401/12 flashing backlights question

Here's a couple of photos full board and led driver section. I have been round with the soldering iron touching up a few joints but found nothing suspicious.
I did change u8106 with a one from another Philips board but made no difference.

[Diah]

Re: Philips Pus 436401/12 flashing backlights question

thanks for the photos.. did you remove one syns R on the LED- circuit or it was so..
you have open circuit at LED- so no booster enough they used 2 in one. i would start to test out side the boards beginning from D8104 /5 and the 2 8pin soc chips.. the load heating lasting on them are so much that they could be cut out one of there pins..