DOWNLOAD LG 42PC51-ZB (CHASSIS:PP78A) Service Manual ↓ Size: 13.48 MB | Pages: 39 in PDF or view online for FREE

- 17 -

1) Minute discharge does not occur at module.
2) Front LED does not activate.

Plug in the power cord

Start Check

No

Yes

Is the power cord
plugged in? 

Connect the cable.
Plasma(CN1)

No

Yes

Are the line filter and
PSU connected?

Replace the fuse.

No

Yes

Is the correct fuse for

the PSU in place?

Plasma(F101)

Connect the 13-14pin cable.

Next remove all cables connected to the PSU and
switch the AV voltage to manual.
If the ST-by 5V does not operate, replace the PSU.

No

Yes

Is the PSU and 13-

14pin cable connected

to the VSC board?

- 18 -

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

- 19 -

1) No OSD or image are displayed on the screen. 
2) The front LED remains green.

Check the PDP Module

Replace the
Power board.

Does

minute discharge

at Module?

Is the inverter

/VaVs on?

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

Yes

No

No

Is there a fault with

the link cable?

Yes

Is the output for the

IC500 normal?

Reconnect the link cable in
P803(Plasma).

No

Replace the VSC.

No

Yes

Check the power.(L1103)

Is the 

video output of the

Tuner normal? (Check

TU400_Pin13)

Is the

input voltage

normal?(Check

Pin3)

Is the I2C communication normal?
(Check Pin9, Pin10)

Yes

No

Yes

Is the LVDS

Cable connected?

Yes

Change the IC(IC500)

Re-insert the cable.

No

No

Check the Tuner.

No

A

Start Check

- 20 -

Is video input of

the A/V jack normal?

(Check R172)

Yes

Sam as Block A

Check the input source.

No

Is the video input 

of the A/V jack normal?

(Check CN703

Pin9)

Yes

Sam as Block A

Check the input source.

No

Is the video input 

of the A/V jack normal?

(Check CN703 Pin1,

Pin3)

Yes

Sam as Block A

Check the input source.

No