PHILIPS LCD TV 32PF9631D/79 Intermittent Display when turning power on

[wedgetail]

The TV has an intermittent problem. Previously by turning power off at the wall outlet for 30 to 60 min and then turning power on again the display come on and stay on.  Now the display mostly turns on very briefly (or not at all) but the remaining functions not needing display works.

From what I can observe it is just the display turning off, sound and channel changing with remote control still working fine.

My  first assumption  has been that it has something to do with the LCD display power supply so I have now taken the back off looking for bulging electrolytics.  Unfortunately for me these all look in good condition.

Now my aim is to get hold of a service manual if possible.  I have searched the internet but not yet found much on this particular TV model.

https://www.eevblog.com/forum/repair/philips-32pfs413212-lcd-tv-repair/25/

In above topic I found a Philips model but only the 32" size , and some guessing from the manual is useful for me at the moment.  Still looking on EVBlog Forum. 

Have taken some pictures, attaching for information.

Any suggestions for what and how to check next step?  Where to find a manual


 

[JKKDev]

You should determine whether it's a backlight fault or other. You can do this by shining a light at the display. If you see anything on it (ofc if there's something being displayed) then you have a backlight issue. If you see nothing and you are sure there should be an image then there's something else wrong.

Are all the PSU fuses ok?

[wedgetail]

JKKDev
Thanks for reminding me of this, I think I did check for this some 18 month ago when it first failed but I do not remember clearly if I did, as in the mean time I have checked other pc monitors for similar faults.  Since I reconnected the power cable and turned the power on, it has not failed, I just now checked and of course the display worked fine. 

I have left the cover off for the time being and see what happens in the coming two days.

Will keep looking or a service manual.

[wraper]

It's backlight inverter protection kinking in. Usually happens due to bad capacitors in PSU/inverter, bad inverter transformer secondary winding or bad CCFL lamp.

[Rasz]

2006 1366x768 tv, do you really want to fix it?
https://elektrotanya.com/philips_bj3.0e-la_chassis_sm_2.pdf/download.html
surprisingly its LED backlight, probably fried leds = laborious disassembly of the panel itself

[wedgetail]

Rasz
Thank you, the service manual looks like the one that is needed. Now i know where to check voltages initially and commands to turn on the diagnostic options as well. The manual will provide me with a lot of reading while I expect to be in self isolation for a number of weeks.  Corona virus has come to our little Island.

As far as repairing I am not in the repair busines just a retired industrial electronics engineer and prepaired to have a go. I think it is worth having a look and figure out if it is a simple job in which case it will allow us to continue watching on a 'big' TV. If I have to buy a new I will buy a much smaller physically.  I am past the stage where bigger is better and the cost does not fit well with retirement either.  So if it is simple I will have fun to figure it out.  I also seem to pick up old TV's readily from people wanted to dispose of units.

With the service manual I am hopeful of a logical investigation of the problem.  Presently I have my wife's permission to leave the unit with the back cover removed for a period of time.  It is in the kitchen so we can keep check on it.  As I have mentioned now it has not failed once today, turn on and off 5 plus times.

I hope I will get a chance to report progress and perhaps tinker a bit with the unit while waiting for something to happen.

My quick read did not make it clear to me if it is possible to run blink testing while using the set.  There is also something about computer acces possible which I have no experience with.   

I could also ask if I can expect any helpful information by using the IR unit, if it can be used at all while using the set?

[wedgetail]

Just an update. I have the unit still with the back cover removed. Two days ago I had one 'soft' failure on start up. By that i mean unit started up with black screen so Iturned power off and waited a feww seconds then turned it back on again an it worked.  Very busy with other things so I have left it alone again until next time.

[Nuno_pt]

Does the tv have a T-con board, if so it could be related to that board and the AS19-H chip or the AS15, I've one Samsung here with bad image related to that chip that is very hot, this chip as to do with the gama, check the gama voltages they should be up or down depend on the way you mesure it, but like 2.4, 2.5, 2.6, etc, if you find it to be like 2.4, 2.2, 2.5, 2.6 it's that chip or if it's hot to put your finger in.

[wedgetail]

Nuno_pt
I am stuck in chemistry problem at the moment instead of digging out the manual. Can you give me a quick description of what the board looks like or what it is related to?

[Nuno_pt]

On the Sansumg ones the T-Con board is on the top os the LCD, when the rear are facing you, PS on the middle bottom, dougther board with the HDMI, etc connectors on the left, from that board leaves a cable to the T-Con board and from the T-Con board leaves flat cables to the LCD.

Here is the image of one on ePay < https://www.benl.ebay.be/itm/TCON-BOARD-6870C-0073A-LC320WX2-SL01-F11-FOR-PHILIPS-32PF9631D-LCD-TV/163176571368 >

You can also google "Phillips T-Con board" to see where is locate, most of the problems with image are related to the T-Con and to the gama chip, in the Samsungs are the AS19 and AS15 ones.

Hope this will help.

[wedgetail]

Thanks It looks familiar in your picture link. Especially the connectors.  It is past midnight and I must go to bed but will look in the morning.  ZZZzz....

[Nuno_pt]

On YouTube you got also lots of videos to show.

[Dacke]

Since it seems more stable with the back cover off and judging by the other symptoms it sounds like a thermal issue.  To me it sounds like caps,  but for verification I would first try a blow dryer and gently heat up various areas,  particularly around the power supply area that's driving the backlight.  See if you can make it fail.