Philips 42PFL9703D/79 LCD TV Not powering up.

[Smithy79]

Hi everyone,
Would like to say g'day from Australia. What an amazing forum to stumble across, there is a wealth of knowledge in here, so I'm hoping to take some away with me
My problem as stated in the thread topic is my Philips LCD TV will no longer power up.
I'll put as much info in here as possible to aid in your diagnosis.
A few months ago I noticed if the TV was turned off (not on standby), and I made an attempt to turn it on from the side panel on/ off switch, it would take a couple attempts to finally turn on. The front panel white light would flash a few times and then shut off, it would continue to happen as I pressed the on/ off switch, finally turning on after approx 3- 4 attempts.
However, if we were to turn the TV off with the remote ( to standby mode), the TV would have no issues turning on at all when prompted by the remote control.
In short, if turned off from the side panel or the mains power outlet, the TV would struggle to power up. If turned off via the remote, it would power up fine.
As of Thursday night my 2 yr old turned the TV off at the wall, and now it does not power on at all, no matter how many attempts are made. You hear a small click/ buzz, then the white flashing light does its thing for a few flashes, then shuts down, each and every time.
I have carefully looked at the capacitors on both boards and none seem to be puffed or leaking... Other than those I've no idea what else to look at.
I am an Electrical Linesman by trade, and repair/ modify electric guitars and RC cars in my spare time. So I'm keen to learn and not afraid to have a look. And I am confident with a soldering iron etc.
Thanks for your time everyone...

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Another pic, wouldn't upload multiples ???

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Last one...

[retiredcaps]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Have a read through the FAQ here first.

https://www.badcaps.net/forum/showthread.php?t=25810

[selldoor]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Pictures are not really clear enough for troubleshooting.
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back (in the same orientation) and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed

https://www.badcaps.net/forum/attach...7&d=1280167246

https://www.badcaps.net/forum/attach...6&d=1280167246

https://www.badcaps.net/forum/attach...4&d=1280167246.

Perhaps start with the connectors that go from the power supply board
(Brown) to the Main Board ( Green) Are there any board designations
if so a close up not obscured by the cables would be helpful.

I take it you have a multimeter - set on vDC 200 and with it all connected
plugged in - on at the mains but not switched on put black probe on a ground
screw ( Is it earth in Oz?) and test each pin on the connectors (at this point most will be nil.)

Is the white flashing light you refer to a led on the front of the TV - is it a set number of flashes
before it goes off or random?

[notallbad]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Referring to Picture in post #3.
With a multimeter set to the 2K ohms setting place the probes across the white resistor marked 5WJ 1.2Kohm (bottom right corner), this is with the tv disconnected from the mains supply. You should get close to 1.2K ohms +/- 10% will be fine, if its oc (reads 1) thats your problem. Of course it is better to test out of circuit but should be fine in circuit. Be sure the set has been switched off for a while before testing to give the large caps time to discharge.

Have you checked the fuse located at the very bottom of the board next to where the supply (black and white) lead connects? Though would imagine this would be fine, but needs checking.

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Hi again,

Thanks for the quick replies, sorry i haven't responded sooner. Between looking after the kids and working, finding time to myself is a little difficult.

I haven't had a chance to measure the voltages across the pins yet, however i was able to test the white resistor marked 5WJ 12kΩ and received a reading of approx 11Ω. And the AC fuse tested fine as well.

There does not seem to be any clear designations near the ribbon connectors between the 2 boards, compared to some photos of other models I've seen on this forum designating voltages etc.

Hope the new pics are a little better. looks like i need to clean the top left of my camera lens.

The white LED is on the front of the TV below the panel. Whilst powering up it flashes, then once the TV is on the LED remains on (steady). Currently whilst trying to power up it flashes 5 times slowly then shuts down.

Cheers again Guys

[notallbad]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Nothing looks unusual, in my opinion at least. Other than the brown spots on the PS board around the solder joints, these mostly look like they are the transformer solder joints which do get hot and sweat. Do any joints look like dry joints? Hard to see from the pictures, a close up examination should detect any severe dry joints. Might be worth re-soldering those joints anyway.

Just to confirm, the reading from the 5WJ 12kΩ resistor was 11k ohm, not 11 ohm. Check the range setting your meter was set on.

Just check the fuse on the back of the board in the 4th photo, bottom right hand corner labelled T3A 125V. DMM set to lowest ohms range, should read close to zero. Also the fuse labelled T1A 125V at the top of the same board in the same photo. And the fuse labelled T3.5A 125V in the second photo on the left hand side just above half way up. I'm quite sure these will all be fine though.

Then with a DMM take some readings from all the pins on the 2 ribbon leads (bottom left hand side in the 3rd photo). Black com lead probe on chassis ground and red lead probe on each of the pins in turn with the meter set to 200v d.c range. Some will read zero volts, these are the ground pins, readings you are hoping to get are either 3v, 3.3v, 5v, 12v or 24v.
You will need to keep powering up the tv otherwise it will shut down and no voltages will be present and the test results will be inconclusive. The ribbon cables will need to be connected at both ends, PS and Main A/V board.

[budm]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Can we see the model number tag on the back of the TV? I am looking for the chassis number.

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

My bad, typo.... Yes 11 kohm was the reading from the white resistor.

I tested all the above mentioned fuses and they are ok.

And I've been able to test all the pins from the ribbon cables, the results are as follows, starting with the 10pin cable from top to bottom;

-12
0
+12
+12
+12
+12
0
0
0
3.3

And the 8pin cable gave these readings from top to bottom;

0
1.6
1
2.5
0
0
0
12

Now here's the very frustrating part.
Since pulling the boards off to take pictures and then re-installing them and connecting all the cables back up......
Halfway thru carrying out the tests on the pins, (I was having to keep powering the TV on)... The darn thing powered up and started working!!!!!
I have unplugged it from the wall, let it sit for 5mins, plugged it back in and believe it or not.... She's working again, 1st press of the power button each time.
I'm going to let it sit unplugged overnight to let everything settle again and see what happens tomorrow. I'll post back my results.
I've attached pics of both the label on the back of the panel behind AV board and the label on the back of the shell of the TV as requested.
Also, excuse my ignorance, but on the PS board, the black unit with the 2 copper windings and yellow label BS33711-01 (whatever it is) buzzes quite loudly (I guess not so loud if back cover was on TV) Is that normal?

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

iPad won't upload 2 pics at a time :/

[notallbad]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Unfortunately intermittent faults are more troublesome to fix but at least it happened now before you did anything further otherwise that could have been misleading as to what the fault is, if for example something had been replaced or any soldering had been done.
That is a transformer thats buzzing, you could try as I suggested and re-solder the pins on the under side, these probably have browned marks on them, it could be buzzing because of a dry joint. Of course it could also be the winding insulation beginning to deteriorate. And no it shouldn't be buzzing that it is annoyingly heard either with the case on or off.
At the same time re-solder any other joints that look dodgy, maybe even the pins on the connectors you have tested as these have been disturbed by disconnecting and re-connecting connectors and could also have a dry joint, I'm guessing the connectors fit nice and tight on the board sockets, no loose connections. As the whole board has been removed and disturbed it could still be a faulty cap, a loose or bad cable connection or solder joint.
I am of the opinion that it is that transformer though. Try and apply pressure to the transformer against the board as you re-solder the joints.

If you follow the 2 connections on the board next to this transformer (pink and grey cables), you will probably find that these go to the inverter and this transformer generates the 24v inverter supply. Also if you notice the solder joints on a couple of the blue caps between these connections have browned marks on the solder side, re-solder them too! Please confirm where these cables connect at the opposite end.

[tom66]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Service manual.
http://www.tgohome.com/ServiceManual...&Search=Submit

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Thanks heaps guys,

I'll resolder the mentioned solder joints and any that look like they may need a touch up.
Thank you for the Service Manual, i was searching everywhere for one, but didn't know what numbers to use in the search.. Much appreciated.
I used the service manual number that tom66 supplied me in a new search and check out what i found (see attachment) Reckon it sounds like my problem indeed, do you guys recommend i do this?

Cheers once again, really appreciate the assistance. You've all been so quick to respond and full of info.

Graeme

[tom66]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

That would seem to be a good place to look. Element14 is Farnell in Aus right?

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Yeah that's correct, they have caps instock at $1.50 each. Will be grabbing some this week.
Will post my results.
Cheers everyone.

[notallbad]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

You posted up voltage readings from the 2 ribbon cables, but you seem to have one reading missing, the top ribbon cable should have 11 readings, you have only provided 10, re-check. Otherwise these readings look good comparing to the service manual P.6.48.
Take a reading of pin-2 also with the set in stand-by as well as switched on.

The other ribbon cable seems to have a 12v reading missing, (you have it measured as 0, the pin above the 3.3v reading) now I would think that it is provided by a 12v rail rather than two separate 12v supply lines, so just check those readings again just to confirm.
Also on the 8 ribbon cable you have taken a reading of 1, I believe your meter must be set on a too low of a range to measure this voltage correctly, measure this pin again with the meter on its lowest setting and change the setting until you receive a proper reading, the 1 on your DMM just indicates the measurement is out of range(too high for the range).

At the moment I am not convinced that replacing those caps will help! It won't hurt to change them as it may be necessary eventually, it would eliminate them from your troubleshooting too.

[notallbad]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Hi Graeme

I hope my advice has helped, I am no expert, to be perfectly honest my knowledge is very limited and I probably won't be able to assist much further but glad to have been helpful, of course I shall let you know if I am unable to help further rather than leave you waiting but keep asking questions as someone, I'm sure, will jump in to help.
Tom has come up trumps with the service manual, for a novice like me thats an invaluable tool.

I would question the reasoning to replacing these caps though, I know he is busy and probably helping lots of other people too so doesn't want to spend too much time going into depth as to why to do it but JUST DO IT! I myself usually question everything perhaps to get a better understanding because of my interest in the subject. Let's hope it does in fact fix your problem.

Regards
Rob

[budm]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

I am downloading the big file of the service manual.
The power board you have is the power supply-inverter board combination.
The inverter transformer is the one on the top left of the board, it is driven by MOSFETs running on high voltage (160v) instead of typical 24v power.
The Pink/White, Blue/White are high voltage wires that go to the lamp assemblies inside the LCD panel.
Hopefully, it will be just the cap is needed per bulletin you found for the 3.3V standby power supply.
That is the capacitive coupling power supply (it uses capacitor for voltage dropping instead of using resistor), it looks like it does not get enough power so the capacitance is increased to provide more power.
What usually goes out is the 100 Ohms (100R) goes open, it is for the high frequency spike protection. Should monitor that 3.3v stby to see if it is stable.

[Smithy79]

Re: Philips 42PFL9703D/79 LCD TV Not powering up.

Hello again everyone,

Haven't had time to double check everything yet, gonna do it all when my parts arrive.

Notallbad, thank for picking up my shortfals, I'll get onto them hopefully this week, if not it will be in a fortnight when i return from my vacation. And yes you have been very helpful, any suggestions/ advice is helpful and is much appreciated.

Thru boredom and a little more in depth searching i came across the attached repair notes "REWORK AREA" for my TV.

What y'all think?? Another few things to explore?

Cheers,