LG 42LF561V No Video after backlight repair

[london-freddie]

Hi need help again please, been working on this LG for several hours now and now stumped
Got the tv with a backlight/ brightness fault
Tv worked however the picture was very very dark barely watchable, could see a couple of very much darker patches as if led's had failed
Stripped the screen and found two failed led's one very badly burnt, both short
Replaced the two faulty led's and the backlights now seem to be ok with what now looks like full brightness
Rebuilt the tv and hey presto no Picture now
Been over and over all connections ie lvds
What have I done ?????
When powering on the tv backlights come on lighting up the screen but NO Picture
Help Please will post some pictures in a few minutes as soon as I get them downloaded

[bman4]

Re: LG 42LF561V No Video after backlight repair

I had the same problem with sharp 50. I was shure i riped the tabs but i just made sure to reseat the tcon cables and it came back. It was same style plug and it.looked pluged in and just pressed alittler harder. Hope its as easy as this or a surge killed a board. This. Is a set with a seprat tcon so Test the fuse on tcon. the xd chips like to fail on the aio main tcons but idk about that one. I see it has no heatsink.

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Pics of boards

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Tcon fuse is ok

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

removing left and right connections one at a time from tcon to lcd makes no difference, still no video

[bman4]

Re: LG 42LF561V No Video after backlight repair

Do u got.12v

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Got 13.3v at tcon fuse

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Looks like I have 270v at + to backlight

[bman4]

Re: LG 42LF561V No Video after backlight repair

Try only one side of the tcon to panel at a time and see if you get a.white screen.

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Yes did only try removing tcon to panel ribbons one side at a time, neither ribbon disconnected made any difference to screen, no white screen on either side

[vinceroger69]

Re: LG 42LF561V No Video after backlight repair

on the tcon the two ribbon cables going to the lcd panel pcb, have you re seated them in that end under the black plastic.

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Yes sure I have reseated them well but will recheck again now

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

just reseated both ribbons no change still no video

[budm]

Re: LG 42LF561V No Video after backlight repair

https://www.badcaps.net/forum/attach...9&d=1542229704
T-CON board has Voltage test points that I can see some of them in your pictures:
Vin, HVDD, VGH, VGL, VCC, VCOM, etc. you should test them to see what they have.

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Hi again budm, as suggested I just checked tcon board voltage test points 12 in all including vcom, vst etc. No test points showed any readings, every test point showing 0V

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

Hi just tried same test on tcon test points with both ribbons removed between tcon and panel, still no voltages measured at any of the test points, only seem to have 13.3 at the tcon fuse
all power board voltages appear ok

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

I am thinking I have a failed tcon or mainboard, unless anyone has any other ideas, but I am only guessing now

[Andrew F. Ali]

Re: LG 42LF561V No Video after backlight repair

Is that 13.3 Vdc on both sides of the T-CON fuse? Are the Panel edge Bds. free and not touching any metal parts of the chassis? Are the cables to and from the T-CON inserted correctly and not upside down, especially the LVDS cable?

[london-freddie]

Re: LG 42LF561V No Video after backlight repair

yes 13.3v at either end of tcon fuse, panel edge boards not touching any frame parts, cables fitted correctly

[vinceroger69]

Re: LG 42LF561V No Video after backlight repair

have you got a scope to test the lvds signal wires usually pairs i think if you press the remote whilst testing in sure you should see some signal on the wires maybe budm etc can advise more on this test