Philips 37PFL5405H/12 PLHD-P982A

[ducky29]

Hello. Im having troubles with the backlight. Tv works fine, sound picture is ok during the whole time but the backlight turns on and off cyclically

I got these measurement from the Power supply
CN6- Connector on top
Backlight on - Backlight off
STATUS 2.8V - 0V
NC --
ADM 1.6V - 1.6V
DIM 3.3V - 1.7V
BL_ON 3V - 0V
GND --
GND--
12V 12V - 12V

CN5- Bottom Connector
NC --
GND_SND --
V_SND 24V - 24V
12V 12V - 12V
GND --
STANDBY 0 - 0V (3.3V present if PSU is in standby)
3.3V 3.3V - 3.3V




I already changed the backlight chip OZ9977BGN.
Im out of ideas. Any help is appreciated.
Thanks.

[neilc6]

Re: Philips 37PFL5405H/12 PLHD-P982A

Backlights flashing I would suspect bad backlights. Did you remove the panel to observe the flashing to see if any are out?

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A

Nope I still haven't checked the ccfl. I never have had bad backlight except for few sharp models. I think ill take it apart tomorrow and will report back.

To be more precise about the fault it looks like a bootloop(like its a software error) but there is sound.

[neilc6]

Re: Philips 37PFL5405H/12 PLHD-P982A

Quick google search says the TV is LED and not CCFL. If TV is rebooting, then main board is suspect if standby voltage is stable.

[R_J]

Re: Philips 37PFL5405H/12 PLHD-P982A

This power supply PLHD-P982A is for a tv with ccfl's , Post pictures of YOUR board.
There is also a high voltage distribution board that will connect to the power supply high voltage to the ccfl's, they can develop bad connections in the connectors, or there could be a broken ccfl.

[neilc6]

Re: Philips 37PFL5405H/12 PLHD-P982A

This is why Budm always ask that you post pics of the entire back of the TV. It will be obvious if the TV is CCFL or LED.

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A


Here is a clear picture of my board. Its ccfl with a power supply + inverter. I also checked the transformer. The resistance of the windings looks good enough.

Is there any way how to disable protection for this board? I run few google searches but without any relevant result.Backlight Ic is OZ9977BGN.

[dick_barton]

Re: Philips 37PFL5405H/12 PLHD-P982A

With your meter probes on each leg of c607 is the voltage steady or fluctuating?

Does the set have Ambilight that you can turn off.

Service manual https://www.manualslib.com/download/...l5405h-05.html

Page 78 shown connector 1M99 pin 7 as Backlight Boost. Perhaps the voltage at that pin is not steady?

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A

Voltage on c607 is 390v and steady. That looks a bit high in my opinion but since it dosen't fluctuate I think its ok.

There is no ambilight. I did a visual check up on lamps and they all look fine, they tend to be pink if they fail.


1M99 Connector is CN6 that I have listed on my first post.

CN6- Connector on top
Backlight on - Backlight off
STATUS 2.8V - 0V
NC --
ADM 1.6V - 1.6V
DIM 3.3V - 1.7V
BL_ON 3V - 0V
GND --
GND--
12V 12V - 12V

Pin7 is GND in my case.

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A

Update: Checked all caps they are good.

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A

Update verified that the screen lamps are working correctly by using another screen.

[R_J]

Re: Philips 37PFL5405H/12 PLHD-P982A

Update verified that the screen lamps are working correctly by using another screen.

You used another "screen"? what do you mean? Did you Connect this lcd panel to another power supply and the ccfl's lit up ok?

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A

You used another "screen"? what do you mean? Did you Connect this lcd panel to another power supply and the ccfl's lit up ok?

I connected the power supply to another panel and same fault is happening.(backlight on-off).
Just to make sure I then connected a similar power supply to the original panel and the lamps stay lit.

[dick_barton]

Re: Philips 37PFL5405H/12 PLHD-P982A

It may be worth checking the orange capacitor close to R517
Also the HV capacitors C401 & C406

[ducky29]

Re: Philips 37PFL5405H/12 PLHD-P982A

Already checked C401 and C406. Will check the orange cap and will report back.

[dick_barton]

Re: Philips 37PFL5405H/12 PLHD-P982A

Also worth checking the solder joints looking for any cracked or poor joints on the transformers T701,T702 T703 or mosfets Q706 to Q709 and CN3, CN4 connectors