Philips 42PFL7482 power suply problem

[soundfinch]

Hello All
found this site from google and hope there is some one out there who can help me with a problem with a Philips tv . The Tv would not turn on. After investergation and internet i found 3 blown caps on the powersuply ( Model No ADPF24300R1P) and 1 of the connector had got hot so removed it and wired straight to the board( I could not find the same connector). The power lite on the TV now comes on and flashs when using the remote but the Screen still dont turn on.
Any Ideas

[PlainBill]

Re: Philips 42PFL7482 power suply problem

Hello All
found this site from google and hope there is some one out there who can help me with a problem with a Philips tv . The Tv would not turn on. After investergation and internet i found 3 blown caps on the powersuply ( Model No ADPF24300R1P) and 1 of the connector had got hot so removed it and wired straight to the board( I could not find the same connector). The power lite on the TV now comes on and flashs when using the remote but the Screen still dont turn on.
Any Ideas

Check the voltages out of the power supply.

PlainBill

[soundfinch]

Re: Philips 42PFL7482 power suply problem

I checked the voltage out puts on the suply and there only seems to be voltage on the 12v output.nothing out of the 24v or the pin thats saids standby. I did this check with the board removed from the TV.
I have attached a PDF of the supply i got from this site if this helps

[PlainBill]

Re: Philips 42PFL7482 power suply problem

I checked the voltage out puts on the suply and there only seems to be voltage on the 12v output.nothing out of the 24v or the pin thats saids standby. I did this check with the board removed from the TV.
I have attached a PDF of the supply i got from this site if this helps

Thanks for the PDF. That makes this easier. Also, thanks for providing details on the testing methodology you used.

This is a variation on the supply that is in most TVs. The 12V supply is the standby supply, and is on at all times. I'm guessing that the main board uses either a linear regulator or a bucking regulator to drop it to 3.3 volts. IC907 is the SMPS controller for that supply.

The main supply is controlled by the Standby input. If I'm reading the schematic correctly, when standby is pulled high (typically 3.3 volts), power is fed to both IC902 (pfc controller) and IC904 (Main SMPS controller).

A 10K resistor from the 12V out to the Standby input should turn on the main supply.

PlainBill

[soundfinch]

Re: Philips 42PFL7482 power suply problem

After connecting a 10K resistor between the 12v and standby . I got between 23.5v to 24v( Fluctuating) on the 24v outputs.
So i will have to investigate more as it seems the power supply is working now.
Thanks .I will now check to see if i can see anything on the mother board

[soundfinch]

Re: Philips 42PFL7482 power suply problem

does anyone have a PDF of the motherboard for this TV as i am having trouble finding one on the net
Thanks

[PlainBill]

Re: Philips 42PFL7482 power suply problem

does anyone have a PDF of the motherboard for this TV as i am having trouble finding one on the net
Thanks

How about a complete service manual? I haven't checked it, but Philips usually has schematics on the main board. Choose one of the larger files - sometimes someone trims the schematics to reduce the size of the file.

PlainBill

[soundfinch]

Re: Philips 42PFL7482 power suply problem

OK put the power supply back in the TV and turned it on. It powers up and goes in to stand by mode but still have no Picture. this problem has come up on this site a few times but i cant work out where to start looking for the problem.
Anyone with any idea please help.

[PlainBill]

Re: Philips 42PFL7482 power suply problem

OK put the power supply back in the TV and turned it on. It powers up and goes in to stand by mode but still have no Picture. this problem has come up on this site a few times but i cant work out where to start looking for the problem.
Anyone with any idea please help.

OK, cue in standard lecture #5. There are a number of failure modes of these TVs. By understanding normal operation it is possible to direct your troubleshooting efforts to the proper area.

All LCD TVs larger than 20" seem to use the same design concept of a dual (standby and main) power supply with PFC front end (all on a single board). When the TV is plugged in the standby supply provides power, typically 5 volts, but I've also seen 12 volts used.

That standby voltage goes to the main board, where is powers a standby processor, or the standby section of the main processor. When the power button on the control board or the remote is pressed the standby processor sends a control signal to the power supply, turning on the main supply. This activates the PFC front end, and also the main and inverter power outputs. Typical voltages are 5V, 12V, 24V.

Back on the main board a signal is sent to the inverter, turning it on and a startup check is performed. Sometimes the inverter status is checked, sometimes it isn't.

Points to check - is the standby supply working? Does the control signal come back from the main board to the power supply? Do the main outputs of the power supply come up? Is the inverter control signal sent to the inverter? Do the backlights come on? If a signal source (picture and audio) is provided, can you hear the sound and see the picture? If the backlights never come on, can you see a picture if you shine a bright light at the screen?

PlainBill

[soundfinch]

Re: Philips 42PFL7482 power suply problem

thanks Bill
just pluged in progam into tv and have sound and can see picture if i shine a lite at the screen so i guess the back lite is not working.
as im a novice at this what should i be looking for to repare this

[PlainBill]

Re: Philips 42PFL7482 power suply problem

thanks Bill
just pluged in progam into tv and have sound and can see picture if i shine a lite at the screen so i guess the back lite is not working.
as im a novice at this what should i be looking for to repare this

A problem with the inverter.

OK, I'll be helpful. If you haven't already done so, pull the back off the TV and take a picture. For best results, we prefer at least 1000 x 1000 pixels, and it must be well lit. Attach the picture to your next post using 'Manage Attachments' - below the test entry area.

If you already know what the inverter looks like, check the fuses.

PlainBill

[soundfinch]

Re: Philips 42PFL7482 power suply problem

Here are the Picture of the inside of the TV.
As you might noticed due to one of the connectors being burnt i connected the wires straight to the board of the power suply. I also replace 3 caps on the power suply

[PlainBill]

Re: Philips 42PFL7482 power suply problem

Here are the Picture of the inside of the TV.
As you might noticed due to one of the connectors being burnt i connected the wires straight to the board of the power suply. I also replace 3 caps on the power suply

First problem. Check on the opposite side of the TV, I suspect you have another inverter over there.

Second (possible) problem. When testing it is a very good idea to fasten each board in place with at least two screws to ensure you have a good ground.

Third problem, while the pictures are excellent for an over-all view, the @$$$#^#!! inverter is too long to see anything useful. If these suggestions don't help, three pictures of each inverter may be necessary.

Check for fuses on both the master (shown) and slave inverters. The component identifier should start with an F (F01, for example). The small white object to the left of the power and control connector may be a fuse; the three larger black objects further left may be fuses.

Check the voltages on the inputs to master and slave; also check the control lines. I note there appears to be a label indicating the functions of the pins.

PlainBill

[ryan74]

Re: Philips 42PFL7482 power suply problem

looks like the same guts i have in 42pfl5432d