LG 42PC3D Main Board Problem

[Edintexas]

I have a question regarding an LG 42PC3D-UE main board.

Initially I suspected the SMPS so I replaced all the electrolytics on the secondary side just as a precaution. All the voltages are present and correct.

This TV powers up, there is screen glow, but it won't respond to commands or accept inputs.

That is, until I press SW4001. This is a small momentary switch located just below and to the right of the RF module on the Main Board (this is the UE version so there is only one main board). As soon as this switch is pressed the TV accepts input, displays a good picture and sound, allows menu access and inputs.

In other words, the set is dead until I pres SW4001. After that it's fine.

Any time the power is cycled I have to press the switch again.

Additional info:
Cycle on time is 10 seconds from pressing the power switch to steady green status LED. Status LED flashes green during that time.

Cycle off time is 10 seconds from green to red. The set turns off as soon as I press the power switch but the Status LED remains green for 10 seconds before turning red.

Sure would appreciate some help with this Main Board.

Ed

[Diah]

Re: LG 42PC3D Main Board Problem

i dont think the issue as you wrote set are deat untill you press SW00X
turn on the set as you did to have good picture and go to setting make sure under setting "last state" to be "ON"

[Edintexas]

Re: LG 42PC3D Main Board Problem

i dont think the issue as you wrote set are deat untill you press SW00X
turn on the set as you did to have good picture and go to setting make sure under setting "last state" to be "ON"

Thanks, but the menu tree settings on this TV do not have a "Last State" option.

I found the service manual for the -UE version.

It shows SW4001 in the ATSC Tuner section as "EJTAG_RSTb" on pin 1 of IC4004, which is a voltage sensor. It appears to pull the EJTAG line and pin 1 of IC4004 to ground when pressed. Normally it appears that these are at 3.3Volts.

There is a 10uF capacitor in this circuit. I think I'll try replacing it and see what happens.

So reseting "EJTAG" and Pin 1 of IC4004 brings the TV on.

I have no idea what EJTAG is!