LG 42PA4500-UM won’t power on, red standby light on, here is what I know (I get sound).


Novice Member
I have an LG plasma 42” that stopped working one day. Red standby light is on, when I power it on with remote, it blinks once and does nothing. No picture no sound, nothing but red standby light.

I took it apart and tested the voltages, to the main board (17v) standby (5.2) vs (206) and I don’t get these values but when I turn the power on, it jumps to 17 for a second before dropping again, same with standby jumps to 5.2 then drops, and Vs is only 0.7 and only jumps to 1.4 ish. Never 206. The red led come on the main board for a second then goes out.

If I unplug the cable from the PS (Power Supply) to the Z sustain board, the tv powers on, red led light on main board stays on, I have sound from cable tv, no video, and all my voltages are correct (17v, 5.2 and 206v).

If I do the same and only unplug the cable from the PS to the Y sustain board, same thing audio no video, all voltages are accurate. Exact same scenario.

If I have both cables from the PS to the Y sustain and PS to the Z sustain unplugged at the same time, same thing, exact scenario with both unplugged, sound but no video, and correct voltages. It’s only when they’re both plugged in (everything connected as it should be) that the tv doesn’t power up, no sound of course and voltages are only correct (for most) for the one second when you hit the power button to turn the tv on. Vs is not correct in this situation.

Does that mean either my Z sustain or Y sustain is bad? Or something on the power supply related to both of them connected up together? I have no clue what to test now or how to determine the culprit from here. All capacitors look fine, I tested all fuses they’re all good.

Help and advice would be greatly appreciated! Thank you.

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