lg50pz570t sound no picture

[daphney]

up until the other day this tv was working fine & then i came back into room & no picture when u turn on screen flashes for a second then nothing. i have pulled back off & theres nothing obvious so was hoping some1 could tell me where to start looking for the fault
many thnx as always

[stj]

Re: lg50pz570t sound no picture

start with a better description.

does it go off,
or does the sound work?
if the sound works - point a torch at the screen and see if you can see a picture

[tom66]

Re: lg50pz570t sound no picture

It's a plasma so don't bother with the flashlight.
Try checking Vs, Va, Vsc and -Vy voltages.

[daphney]

Re: lg50pz570t sound no picture

vs = 203 va =55 vsc = 152 vy =190
vs & va where both test points & meter neg on earth screw vsc & vy is resistor & had leads on either side of it to get those readings hope thats correct if not i do again
many thnx as always

couldnt see -vy have i tested last 2 wrongly & should have earthed meter???

[daphney]

Re: lg50pz570t sound no picture

vsc with meter on earth screw + 76 - 76 vy on earth screw 116 -74 is +vy on board cant see any -vy only + - on that resistor
thnx sorry ifi being a dumbass

[tom66]

Re: lg50pz570t sound no picture

-Vy and Vy are the same. That's OK.
Does LED on control board blink?

[daphney]

Re: lg50pz570t sound no picture

yes it does pattern is 3 quick blinks with mayb 1 sec gap in between then fourth blink is longer then a gap 4/ 5 secs & starts cycle again
many thnx as always

[tom66]

Re: lg50pz570t sound no picture

Is Vzbias on the Z-sustain OK? Any glow from panel?
Have you tried "ext auto gen"?

[daphney]

Re: lg50pz570t sound no picture

vzb = 119.6v with neg of meter on earth screw & same if on + - of resistor screen does glow
not as bright after intital switch on but still glows till turn off & no to last bit how do i do that?
many thnx as always

[daphney]

Re: lg50pz570t sound no picture

vzb = 119.6v with neg of meter on earth screw & same if on + - of resistor screen does glow
not as bright after intital switch on but still glows till turn off & no to last bit how do i do that?
many thnx as always

[tom66]

Re: lg50pz570t sound no picture

For EXT AUTO GEN, I need a picture of your control board to show how if you have not done it before.

[daphney]

Re: lg50pz570t sound no picture

board no is ebr71727802 if pic not clear enuff i take more
many thnx for all u help

[tom66]

Re: lg50pz570t sound no picture

OK - it's the two holes above "LG PDP 101019"
Jumper them with a piece of wire.
Unplug the right hand wide ribbon cable which goes to the main board.
Power on the set. You should see cycling test patterns like this:
https://www.youtube.com/watch?v=9Lcq...k&noredirect=1

[daphney]

Re: lg50pz570t sound no picture

just done that & is same as in vid clip
thnx

[tom66]

Re: lg50pz570t sound no picture

Most likely a bad main board then. Small chance of control board being bad but very low.

[daphney]

Re: lg50pz570t sound no picture

ok thnx for all your help i will look & let u no how i get on
many thnx as always

[daphney]

Re: lg50pz570t sound no picture

i replaced main board with 1 from smashed screen tv & working great thnx for all your help