SOLVED : Philips PFL5507K/12 backlight come on for a second

[frake50]

Hello every one,

i got this set from friends, and it had fault, that when i power it on the LED Backlight come on fro a seond and show on the LCD the sand clock, then backlight go off the TV keep on,

with torch lamp can see the Picture normal as well the sound. RC control working fine.

the power board had integrated LED Inverter from Delta DPS-119AP , i found Diagram of this part, but there no much Value on it.

this why i am here to asking if any of you faced same Problem, and which Part on the PWB fault ? 

Any suggestion appreciated it.   

[jordan]

Software update

[frake50]

Thanks Jordan,
of sure the first things i did make update and write it again both software,  main software and standby software.  they are not the reason.
its 99%  PSU,  1% LED string,  but the string lines i had all checked by trick i use always with TOSHIBA  which had same panel from samsung, by add 10 Ohm Resistor parallel to the line to trick the Protector that no one LED OPEN.  and the result was all line do the same by add the 10Ohm coming on for 1 second at start up..

[downunder]

This sounds interesting. Where exactly did you connect the 10 (100) ohm resistor to test the LED strips? Please explain.

Bruce

[frake50]

from LED driver, there will be always plug going to the LED strips, 4 white and one Black,   black are mass. and the 4 white are regarding to LED strips,  those just separated them, and one by one cut and add parallel 10 Ohm 10 watt Resistor to dummy the driver there are no open LED. at the right Line all LED Back light will turn on....  if the Problem with them as OFF mean there no fault at strips.

this is regard all Samsung Panel or LG. which used by most other LCD TV brand.  like Toshiba,  at Toshiba always this happen by Panel size 46. 

other way to know if there are LED fault at strips with out need to take LCD out. just i disable the protection if the TV came with LED Driver separated from Power Supply.  just took the plug out which between PWB and LED Driver and plug it again this will trick the protection, and LED all come on. this method specially useful by TOSHIBA.

Back to my problem,  still i do search on defect Parts on the PSU 

[downunder]

Heck, I'm not all that much wiser. So one by one you cut the supply leads to the LEDs and put a 10 ohm resistor where......in series with the lead you've just cut, or in parallel.....parallel with what. It's not clear to me.

I'm always interested in new shortcuts in fault finding, but this sounds a bit iffy to me.

Bruce

[frake50]

Take look on the Photo attached. where to place the 10 Ohm to test.

[downunder]

I see, so the resistors are in series with the supply lines to the LED strips. Not too sure what this achieves...need time to digest this, as "Still Open All Hours" happens to on telly.

Bruce

[frake50]

will work perfectly as usual to work.  as the protective will understand there are no open LED at Strips, and the one less LED at back light had no much effect on the Brightness of the Picture.


EDIT:
Problem solved  C706  628J 630 V. replaced with 6800PF 1000V 

[downunder]

Nice one, Frake. Thanks for sharing. On the PSU board, was it?

Bruce

[frake50]

Yes on the PSU, its regarding the HOT of the Back Light.

attached PHOTO for PSU DPS-119AP for References

[downunder]

Yeah, that would certainly put a spanner in the works.                   Bruce

[Turnip]

Hi Bruce - Curious,

Guess a ten ohm series resistor might confuse inverter as to a dud Led, could be useful, but surely still have to change the duff Led at some point, even if to replace with a zener diode.

Was happy to discover on my first one, that with Led lenses and curious sheets of plastic, could get away with more than I suspected.

Admit some replacement Leds were of a slightly different colour, and lenses applied haywire, as couldn't recall original orientation.

No problems - But just the first one - Chris.