Fixing Phillips LCD TV 37PF7320A

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

OK, I look at the SCH, it is not very details, from what I can on the power supply block diagram, it only shows the +24v dc power connection (5 pins), the other 5pins on the inverter are for the ground return, but it does not show the pin 11 and pin 12 which are for dimming and BL_ON controls. What do you see on these two pins?
You will have to trace out these two pins where they go to on the AUX POWER board, they should be routing through this board and go out the main board some how. You should download the service manual for this TV.
This is not going to be an easy task to trace this out.

[RobPhotoPro]

Re: Fixing Phillips LCD TV 37PF7320A

There's no voltage on pins 11 and 12. I have the service manual, but no idea, how to troubleshoot or trace missing Bl_On. In the start-up sequence it looks, the backlight is turned on as last. The fact, that motherboard doesn't send the signal can be caused by many factors and the problem can be anywhere. I would love to isolate the faulty board at least.

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

The bad part is that the service manual does not show where those two pins are connected to, that is why you will have to remove the AUX power supply board and trace that out, that is what I would do.

[RobPhotoPro]

Re: Fixing Phillips LCD TV 37PF7320A

The question is, if the Bl_On is generated in the mainboard or in the AUX PS board. Also, the reason the Bl_On is not generated can be caused by a problem in the main board or AUX PS board, but also in the Power Supply board - maybe the mainboard doesn't detect some voltage or detects a different problem and that's why it doesn't turn on the backlight. How do I find out, what the cause is?
I wish I had the same working TV here to swap some boards. That would be much easier.... :-)

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

The CPU on the main board generate the BL_ON command and sent it out through the AUX POWER SUPPLY board in your TV. Most brand will send the BL_ON through the main power supply, it goes into one connector of the power supply and flow right through another pin on the power supply, mainly for cleaner wiring of the TV. We are trying to find the way to turn on the backlights so we can see if the pictures look OM or nor, otherwise you may also have another problem, we just need to have the light source to light up the screen, who knows, you may also have bad T-CON board also.
This is an indepth troubleshooting.

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

Unless somebody here has the same chassis of this TV can chime in and tell us what he/she has on the working TV.

[mauibuzz]

Re: Fixing Phillips LCD TV 37PF7320A

Thanks PlainBill, for the tips on this Philips Tv, It was the 100ohm resistor on the Power Supply board, Good Call!

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

Same resistor as shown on my post 34?

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

On the resistor does it usually go hi ohms when it is bad i am getting in meg ohms reading

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

I that the resistor was open but i also thought maybe i was not getting good contact.after taking a picture there it was i could see burnt mark.the only thing in diagram i believe it shows it as 470 ohm resistor i will use bands to see what it is .

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

Here is a better picture

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

Looking at color codes bands shows like 800 ohms resistor is this correct or am i reading it wrong

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

I cannot easily see the color. Can you tell us the color of those bands? also show the bottom side of the board so we can see how it is connected to the other components

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

Here pics

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

Pic

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

Ahh, one of those failed R3118.
470 Ohms 5% 1W Flame proof Metal Oxide (MOX).

The one I worked on (it uses the same setup) had 100 Ohms 1/4W, I changed my to 100 Ohms 1/2W.

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

Thanks for help i will buy resistor and see if that takes care of problem

[ricosavy]

Re: Fixing Phillips LCD TV 37PF7320A

Replaced the resistor put in 470 ohm 1 watt 2% flameproof and now tv is working.Thanks for your help Budm.

[budm]

Re: Fixing Phillips LCD TV 37PF7320A

Thanks for the repair feedback.

[pvkq]

Re: Fixing Phillips LCD TV 37PF7320A

I have a different power issue with my 37PF7320A/37B LCD tv. After plug in the tv, I can hear one click, the red led flashes once, the green led lights up for a couple of seconds, then another click and every thing goes dead. Press power button, nothing. A funny thing is if I turn off power (unplug) to the tv after the first click, the back light comes on for a second. But if I turn off power to the tv a few second after the second click, no flash of back light. I already checked resister 3318 and it is fine. All caps on power board and AUX power/audio board look fine. I also measure AC at the main rectifier and it is 0V after the second click. I need help. Thanks.