any LG plasma techs on here. bad picture on 50"

[mzone]

hi guys.

i managed to get hold of a 50" LG plasma 50pm680t

set originally had a problem with just 2 thin black horizontal lines going all way across bottom of screen ( picture was perfect apart from this)

i put this down to a faulty lower buffer or the screen tab needs reseating.

however what happened is i forgot to clip the blck screen tab connector on buffer down on switch on silly me.
so im guessing its shorted the buffer and might of shorted the y-sus


now the symptoms i get are just black picture. however i removed bottom buffer completly and just left top buffer in and i get like a mal-discharge effect like in picture i attached. sometimes the picture is just colored dots appearing on screen.

so for sure the bottom buffer has shorted.as its just black with both buffers in tv.

my question is does this look like a blown y-sus or buffers or -y-sus and blown buffer?

[t1412]

i would say control board fault, have you tested vs/va voltages

regards
shaun

[mzone]

im guessing the control board is ok concidering there origanally was a good picture.

i think what happened was as i forgot to clip the black bottom buffer screen tab clip down on switch on, it must of shorted the bottom buffer, in turn this shorted the y-sus.

as its just black if both buffer in tv and colored dots if i remove bottom buffer and leave top buffer attached.

from memory working with lg tvs removing the faulty buffer will get the picture working again & there should be at least half of a picture depending on what buffer is left connected if y-sus is ok.

i cant see how the y-sus  would of took out the top buffer too.

i have not worked on a lg for a while but im guessing it might be y-sus problem.

i thought i would ask on here as i know theres a few people who repair lg plasma on here

i have not measured the voltages on the y-sus as could not find the vs test point for this model.

[t1412]

the reason i said control board i had one with a similar fault turn out to be the control board, the smd capacitors on the ysus board can cause  trouble, or has you said buffer board fault, i think tv tony is the man for this   

cheers
shaun       

[mzone]

replaced all 3 boards now have picture once again.

the lines still present through,

i also just found out this is only 10 months old so still in warranty but have no original receipt or purchase date off orignal owner, so i guess the warrenty is useless   im not sure how lg warrentys work

maybe someone one here knows.

the line is similar to this

im guessing prob the pdp. dont think there is anything else it could be concidering i changed y-sus and both buffers already.

[t1412]

nice job

shaun 

[downunder]

LG did have connectivity problems between the Y-sus and Y-drives on some of their models and introduced a modification clip to improve the security of the connectors. Google EAG61050702 for more info.

[mzone]

LG did have connectivity problems between the Y-sus and Y-drives on some of their models and introduced a modification clip to improve the security of the connectors. Google EAG61050702 for more info.

ok thanks downunder

do you know what boards these clips were designed for as the y-sus and buffers in this tv are seen in pictures attached

[downunder]

They're for the 5 white connectors that join the Y-Sus to the buffer boards. Another way to approach this is to disconnect the Main Board from the Power Supply, turn the set on and short out the AUTO GEN pads on the Control Board. The unit will generate test patterns on the screen. If the patterns are clear and free of lines, it means the panel and scan boards are OK, but if the lines present in the patterns and you've replaced the Y boards, it only leaves the panel. Also reseat the flexi between panel and buffer that sits on the same level as the lines on the screen. These can be a bugger and have to fit precisely into their sockets on the buffers.