Lg 50pw450t sound no picture

[gobby009]

hi i have the above tv havent troubleshooted much as unawre where to start things i have done checked the fuse on the ysus board and it read 00.3.left the tv on for 30 mins to check the heatsinks.heatsink on the zsus was very hot heatsink on the power supply warm and heatsink on the ysus warm.thats about as far as i have got as above the problem with the tv is that there is sound but no picture.any help much appreciated.there is a green light flashing on board below the power board.

[Hamie]

Re: Lg 50pw450t sound no picture

Please upload pictures of all the boards singularly.
I need to see the test points.

[gobby009]

Re: Lg 50pw450t sound no picture

hi thanks for your reply these are the boards.

[Hamie]

Re: Lg 50pw450t sound no picture

Ok on the control board. (The one with the green flashing LED)

Connect these 2 holes beside r51 and r52 with a paper clip, but of wire etc.

[Hamie]

Re: Lg 50pw450t sound no picture

Ok on the control board. (The one with the green flashing LED)

Connect these 2 holes beside r51 and r52 with a paper clip, but of wire etc.

[Hamie]

Re: Lg 50pw450t sound no picture

Now peel back the tape, lift the latch, and disconnect the LVDS cable,


Here:




Power on the tv.
Do you get test patterns on screen?

[gobby009]

Re: Lg 50pw450t sound no picture

nothing on screen.turning the tv and it goes straight into standby mode.

[Hamie]

Re: Lg 50pw450t sound no picture

Ok leave the jumper in place, disconnect the z-sus,

power on the Tv.

[Hamie]

Re: Lg 50pw450t sound no picture

Infact, remove the jumper and reconnect the LVDS cable.


Disconnect the z-sus power on the tv.

[gobby009]

Re: Lg 50pw450t sound no picture

nothing,tv does stay powered on with sound but no picture.

[gobby009]

Re: Lg 50pw450t sound no picture

i have also tried turning the tv on with the top buffer board removed no change.i was going to try and do the same with the bottom buffer board but there seems to be something stuck behind the board at the bottom to the chasis like a sponge its pretty rigid so i didnt want to take that board of.

[Hamie]

Re: Lg 50pw450t sound no picture

Ok you need to check voltages.

VS and VA on the power supply.
VSC and VY on the Y-sustain
Z-Bias on the z-sustain.


VY and VSC are measured across a resistor.
Put you probes at the corresponding - +

Post your results.

*please note that the voltages may, rise then fall, so you may need to quickly measure them whilst turning on and off the tv.

[gobby009]

Re: Lg 50pw450t sound no picture

do i check voltages with the tv on? thanks

[Hamie]

Re: Lg 50pw450t sound no picture

Yes.

[gobby009]

Re: Lg 50pw450t sound no picture

ok after reconecting the zsus board to the ysus board the tv turns on but goes straight to standby which wasnt happening before.removed zsus board from ysus board to check the voltages and the powerboard vs is 204 and the va is 54 can you point out where the vsc and vy are on the ysus board.so can i check the zbias on the zsus board in standby?thanks

[gobby009]

Re: Lg 50pw450t sound no picture

ok checked the vsc on the ysus board and it goes from 003 to 001.the vy is 096 these readings are with the tv on and the zsus board disconected.because when the zsus board is connected the tv goes straight to standby which has just started happening since i tried that jumper test.

[Hamie]

Re: Lg 50pw450t sound no picture

Are you measuring the VSC and VY across the resistors?

[gobby009]

Re: Lg 50pw450t sound no picture

yes i put the the 2 multimeter prongs on the resistor 1 on each end.

[Hamie]

Re: Lg 50pw450t sound no picture

And what are the VSC and VY voltages with BOTH buffers unplugged?

[Hamie]

Re: Lg 50pw450t sound no picture

Is this plugged in correctly?
Might just be the camera angle but it looks like it's at an angle.