lg 42le4900 super slim

[jimbofz]

Hi everybody ,this tv has the usual backlight off fault after a few seconds,( sound remains ok)
the error pin from the main board (comparitor type cct) which when tv is ok should be 0v, when it detects error it rises to 3v
which turns off backlight. so far no suprises,
but sometimes the pic from startup is ok then it goes off to black level and the backlight remains lit ,this makes me think possibly main board ic needs reflowing?
i tried it on hdmi ,and aerial i/p ,when i tried the on screen menu ,menu was fine?
could it be i have more than one fault?
or is it likely to be one or more led ,just dont want to strip it right down untill im certain.
ive checked all the normal supplies are ok and no low esr caps this is the lg with the very slim boards with pencil thin electrolytics.
ive soldered the area around the mosfet led drivers ,this has a small green pcb mounted at the top of the psu( led driver board) which looks quite unserviceable,
it seems to me to be over engineered ,far to elaborate method of driving the leds possibly main board main ic needs reflowing? i believe the leds are on the sides ,not the usual strips across,i suppose this is how they made the display unit so slim.
pics to follow.
theres 4 feeds to the b/l:
in red, and each one has 2 returns ,in black,when b/l off ,the returns are: 11v,9v,
11v,9v
11v ,11v
11v,9v

[ReeceyBurger123]

Re: lg 42le4900 super slim

I had one of these super slim ones, the fault was an intermitent Led in the screen bastard to diagnose ! What does Led return voltage go to when the Bl fails ?

[jimbofz]

Re: lg 42le4900 super slim

it appears that theres 4 feeds each 100v when b/l is ok ,0v with no b/l.
to answer your question,
when it fails the returns are all as above,11.3v 9.1v on three of the returns but on the fourth both return pins are 11.3v
did you manage to repair yours? did you replace the faulty led /and if so was it difficult to open to gain acess on this super slim model

[jimbofz]

Re: lg 42le4900 super slim

just got cct for ld03d chassis ,you guessed it ,no details of green driver b/l board ,ive removed it and tested all fets ect but although the board has seen a bit of heat its not excessive .
Because my w/shop is freezing the set can sometimes stay on for 20mins. this at least gives me time to note voltages when its working normally.Using hairdrier doesnt seem to speed up the fault,
How annoying the service manual doesnt even cover the psu!
bring back the g11s