LG 42LB552v no power red light blink twice then off

[elpiko]

Hi I have an LG led tv when power on the red light come on then blink twice then turn off. The screen is completely blank no backlight or image shows. I've check the power supply everything seems ok.

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

Ok so I've changed two opto in the power supply.

When I connect the tv the backlight comes on but no image and the two blinking of red light remains then goes away. If I keep finger on power for few seconds the backlight turn off and red light stay solid but I hear a rapid clicking sound in the power supply.

If I turn tv on again backlight comes on two flashing red light then goes off and the clicking sound stops.

[Repair_dane]

Re: LG 42LB552v no power red light blink twice then off

Try to unplug the main board and turn it on again.
Do the LED's come and stay on?

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

since the power switch is on the main board i wont be able to turn on the tv with the main board disconnected. but ive tried to power it on without the tcon board and the backlight does not turn on.

ive tested all the voltage on power supply going to the main board all are fine.
the strange thing is that the standby light will flash twice then completely off but the back-light remain on till i turn it off from power button then the standby light will stay solid red

[budm]

Re: LG 42LB552v no power red light blink twice then off

1) Please attach good clear pictures fo the whole back side of the TV showing all the boards so we can see what we are dealing with?
2) Your post #1: "I've check the power supply everything seems ok" does it mean all the Voltages and the control Voltages are OK?
3) Your post #2: "Ok so I've changed two opto in the power supply." Are they bad? What section of the circuit are they used in?

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

there are two sets of pin one says power on this all volatage is ok. the one that says drv on i have not test yet.

as for the opto i was not getting any reading from one of them, also i was reading some forum and a guy got the solution by changing the opto so i tried changing both and now i have backlight but no images

[dick_barton]

Re: LG 42LB552v no power red light blink twice then off

What voltage do you have on either side of the fuse on the Tcon board

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

im gettting almost no voltage on these around 0.8v but the one next to it has 8v the fuse is ok ive tested it. check image

[Repair_dane]

Re: LG 42LB552v no power red light blink twice then off

there are two sets of pin one says power on this all volatage is ok. the one that says drv on i have not test yet.

as for the opto i was not getting any reading from one of them, also i was reading some forum and a guy got the solution by changing the opto so i tried changing both and now i have backlight but no images

Main board is the green one that controlls inputs, sound and video. The other one is your PSU. power supply board.

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

yes i know the main board is the green one and the other one is psu and the small one that panel connect to is the tcon.

[dick_barton]

Re: LG 42LB552v no power red light blink twice then off

With the set powered off check the resistance of the fuse. It should read close to 0 ohms.
Did you take the voltage measurent across the fuse and not from chassis to one side of the fuse and then chassis to the other side?

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

i tested the fuse and get continuity so its good also i check the voltage from both side of the fuse and not from chassis.

i dont think its the power supply im suspecting the main board to be faulty. problem is i live very far and shipping is costly and dont have the luxury to order a main board to test i have to make sure before i do as i cannot return it after.

[nomoresonys]

Re: LG 42LB552v no power red light blink twice then off

It's still not clear, we are looking for about 12 volts on each side of the fuse when acting correctly, for this you put red + probe on each side of fuse and the black - probe goes to chassis ground.

[elpiko]

Re: LG 42LB552v no power red light blink twice then off

ok ill check that tomorrow and revert back on the findings