LG 42LW450U

[EVILMRB]

Hi this tv is on standby and when I press the remote the standby led flashes a couple of times really slow then the led goes blue then a click can be heard from the back and the led goes straight back to red. I tested the voltages on the input from the mainboard and I get 12v and 3.5v as well as the 24v but the pin that says PWR-ON 24v reads at 3.4v and when I press the remote the voltage on that pin goes to zero then back to 3.4v. I have heard that these lg tvs have a problem with the mainboard and putting them in the oven.
I have put some pictures up to view

PSU Model No: EAX62865401/8   REV1/0

MAINBOARD Model No: EAX64113202 (0)

[jordan]

Check coil L407 near the power connector, under the glue, on main board, for breaks.

[downunder]

That connector. P201 (on the power supply) that feeds the main board has 2 rows of pins, the ones you can see at the top of the socket, and a row below that you have to access from the back holes in the plug. So you're reading PWR-ON correctly, but 24V is the pin below.

Of most interest is the pin designated DRV-ON, which is the backlight-on signal, again 3.4V approx., which I suspect you'll find missing. The LW series all seem to fall down in this respect. A cook-up in the oven will likely sort it (bad ball joints under the micro) and on your model the heat-sink on the micro is just held on but a bit of silastic at the sides. One I cooked didn't respond, so I put a weight on the heat-sink and tried again, but still no luck.

Those that do recover only last about 5 months, and the customer goes head-hunting for guess who.                      Bruce

[EVILMRB]

Will I be able to use my rework station instead of oven.

[Turnip]

Hi EVILMRB,

Some folks use a preheater and a blast of hot air from the top. On the other hand the oven set to 200C for ten minutes usually sorts the problem without melting anything.

Admit had to replace a couple of melted Scart sockets before I used an oven thermometer.

When it gets to temperature, slip in the board. Turn the heating off, just using the fan to circulate heat. Pretty successful to date - Chris.

[EVILMRB]

Thanks for that, will try once I buy a thermometer. Will post results.

[EVILMRB]

To Jordan you was right, the fault was the L407 coil had a dry just under the glue resolderd tested for more drys in that area switched on all working. Big thank you to all who advised me but especially Jordan.

[jordan]

 

[Wirdy]

Searched for a fix to this fault & I have registered purely to say thank you for this thread & in particular to Jordan, his advice above to look at L407 was my exact fault (cracked dry joint). I'd never have noticed it without the tip, so thank you very much.