LG 42LS3400 - No power

[kisk]

Hoping you guys could help me diagnose this LCD TV. Standby light is solid red when unit is plugged it. On power-on, the standby light flashes 3 times and then stays off. No visible damage, caps look ok, and fuses check out ok (shorted).

Attached is the service manual and some pics of the boards.

Here are the voltages I'm getting off of the pins when the unit is "on". The low voltages seem to be in spec, but nothing on 12 or 24v.

P201:
Left row, top to bottom (see pic for V reference)
--------
87.3 mV
87.3 mV
87.3 mV
0 V
3.576 V
3.576 V
G
G
2.2 mV
3.444 V

Right row, top to bottom
-----------
V bouncing
1.152 V
V bouncing
3.248 V
3.575 V
3.575 V
G
G
2.2 mV
2.2 mV


P203:
Top to bottom, pins 14 to 1
1.152 V
~140 mV
3.248 V
90 mV
G
G
G
G
G
2.2 mV
2.2 mV
2.2 mV
2.2 mV
2.2 mV

In the troubleshooting section, it says to test voltages and to "Check short of Main B/D". How would one go about checking for a short of the main? Not sure I understand this.

Any direction would be wonderful!! Thanks!

[kisk]

Re: LG 42LS3400 - No power

Checked the 2 mosfets on the bottom of the power board as well. Here are the readings, in kOhms:

Q101:
GD = OL
GS = .051
DS = OL

Q102:
GD = OL
GS = OL
DS = OL

Can barely read the tops of these mosfets, but this is the best identification I can make out:
10MN6
ON
6K16b214

Hope this leads us closer

[kisk]

Re: LG 42LS3400 - No power

Well, have a new power board on the way, but if anyone has any ideas I'd love to try them in the meantime. Thanks!

[budm]

Re: LG 42LS3400 - No power

If you look at the bottom side of the board you can see the pins' labels, you can report the voltages of those pins of CN201 so we will know which pin has what voltages.
http://www.shopjimmy.com/media/catal...1-bottom_1.jpg

[jaredwhamilton]

Re: LG 42LS3400 - No power

Bump on this!

Did replacing the power supply fix your issue? I have this same TV, and today it just turned off. When trying to power it on, the red indicator light blinks 3 times and nothing else happens.

I already went and bought a new TV, but this one is only two years old, and it would be nice to repair it and use it somewhere else.

Any input is appreciated!