42PC5RVH-TD (CHASSIS:PP78A) - LG TV Service Manual (repair manual). Page 16

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1) After lighting once it does not discharge minutely from the module. 
2) The relay falls.(there is an audible “Click”.)
3) The color of the front LED turns from green to red.

Is the Power Board

normal ?

Replace Power Board.

Is the output the normal Low/High
voltage except for the Stand-by 5V?

Yes

No

No

Are all the connectors

normal?

Replace the connector.

Replace the fuse.

Replace the Y-Board.

After checking each connector does
is operate correctly?

Yes

No

No

Is the Y-Board

normal?

Is the appropriate

fuse (FS2,FS3) on the

Y-B/D?

Is the output voltage
normal after removing the
P1 connector of the Y-B/D?

Yes

No

No

Replace the Z-Board.

Is the Z-Board

normal?

Is appropriate

fuse (FS1,FS2) on 

the Z-B/D?

Is the output voltage

normal after removing the

P1 connector of the Z-B/D?

Yes

No

No

Is the X- Board

normal?

Is the 

output voltage normal 

after removing the  P100, 110,

200, 210 connector of

the X-B/D?

After removing the P100, 110 and the output
voltage is normal : Replace the Right X-B/D
After removing the P200, 210 and the output
voltage is normal : Replace the Left X-B/D

No

Yes

Replace the fuse.

Yes

Start Check