Intermittent Power On LG 47LV5400-UB

[hackintoshx86]

This is my first problem post. If I miss something please forgive me.

I have an 47LV5400-UB (OCT 2011) that only turns on occasionally. When it has problems, it turns on as if the TV was booting as normal. The LED light stays on. The screen stays off with no backlight or sound.

If you cycle the power a few times it may come on. Once on, all appears as normal. Inputs all work. Except the picture "flashes" every once in awhile on the home screen.

An LG Repair person did a house call and said that the Main Board was the problem.

I have removed both the power supply and main board for testing. I have tested the board to see if diodes, resistors and caps could be the problem.

I did find 2 surface mount caps on the Main Board near the Antenna Input to be low. I did do the test with them on the board in-circuit and I don't know if the readings are reliable. There are 4 caps with all the same 100UF on the main board. Two tested at 105UF. One tested at 63UF. And the last one at 3UF. Could this be my power on problem?

I have seen LG repair kits for the same board for other model TV's on eBay that include 2 surface mount caps. Others report the nand flash has problems as well.

I could order the caps from Digikey and have someone solder them on. But I can't solder that well that small.

Thanks for the pictures from ShopJimmy.com

[dick_barton]

Re: Intermittent Power On LG 47LV5400-UB

Can you supply the legend alongside the two connectors and what voltages are present on each pin when you power up.

(Photo courtesy of Shopjimmy)

EG
CON1
Pin TXT Reading
Pin1 12V 0V

[hackintoshx86]

Re: Intermittent Power On LG 47LV5400-UB

Can you supply the legend alongside the two connectors and what voltages are present on each pin when you power up.

(Photo courtesy of Shopjimmy)

EG
CON1
Pin TXT Reading
Pin1 12V 0V

I will provide the voltages as soon as I get the TV back together.

Are you suggesting that the voltage coming from the power supply isn't correct?

Rather than a MainBoard problem?

[dick_barton]

Re: Intermittent Power On LG 47LV5400-UB

You have to start somewhere. So the first thing is to check that all the voltages are as they say on the legend as printed on the power supply. This should help to remove the power supply as the problem. You can then move onto the next step........

[hackintoshx86]

Re: Intermittent Power On LG 47LV5400-UB

You have to start somewhere. So the first thing is to check that all the voltages are as they say on the legend as printed on the power supply. This should help to remove the power supply as the problem. You can then move onto the next step........

Thank you for the advice. I appreciate it! I will post voltages ASAP when I have it back together.

[hackintoshx86]

Re: Intermittent Power On LG 47LV5400-UB

What voltages would you like me to report or just check that they are okay and matching the legend?

[dick_barton]

Re: Intermittent Power On LG 47LV5400-UB

OK then the connector on the left of the above picture has a legend alongside. Can you use your multimeter and measure the voltages on the 24 pins and write the legend alongside your readings.

[budm]

Re: Intermittent Power On LG 47LV5400-UB

P501 is the double-row connector, the pins that you are seeing on the top side are for the ODD number pins corresponding to the labels of the top row:
Pin 1 (left pin) has white circle marking on it.
Pin 1 PWR ON = ???V
Pin 3 24V = ???V
Pin 5 GND
Pin 7 GND
Pin 9 3.5V = ???V
Pin 11 3.5V = ???V
Pin 13 GND
Pin 15 GND
Pin 17 12V =??V
Pin 19
on and on.
The EVEN pins you will need small tip probe to to the backside of the female connector.

[hackintoshx86]

Re: Intermittent Power On LG 47LV5400-UB

Okay, after the last few days of playing around.

All voltages on the power supply test good. I also swapped the power supply for a known good one to double check.

The main board seems to be the problem. Where do I go now that I know the voltages are good going into the Main.

[hackintoshx86]

Re: Intermittent Power On LG 47LV5400-UB

And thanks for your help with explaining how to test the leads.

[hackintoshx86]

Re: Intermittent Power On LG 47LV5400-UB

If anyone knows of a place to start testing on the main board, it would be appreciated. Thanks

[CoppellTVRepair]

Re: Intermittent Power On LG 47LV5400-UB

Go straight to the main processor.

Board has a standby which rarely ever goes bad and main which BGA usually degrades and needs to be replaced.

http://www.coppelltvrepair.com/p/162...ausylhr-led-tv

[CoppellTVRepair]

Re: Intermittent Power On LG 47LV5400-UB

This is my first problem post. If I miss something please forgive me.

I have seen LG repair kits for the same board for other model TV's on eBay that include 2 surface mount caps. Others report the nand flash has problems as well.

I'd like to comment on that.

There are a few sellers out there who offer repair kits for practically any board they've heard of; if there are SMD capacitors they'll include them and if there are 1117 voltage stabilizes they'll likely include them too.

I have personally received customer's board with a vendor's repair kit consisting of capacitors and 1117 regulators that I have NEVER EVER seen fail on a particular Sanyo main board.

Simply put, there are a lot of vendors that are just riding naive buyers out there.

I know some of them and I know some of their kits.

It is very sad for the industry and those of us who try to actually bring solutions..just as sad as all the kids offering main repairs for $45 and baking boards in ovens, because, let's be realistic about it, there's no way you can do anything more than home kitchen reflow for that kind of money.

[geeforce]

Re: Intermittent Power On LG 47LV5400-UB

Go straight to the main processor.

Board has a standby which rarely ever goes bad and main which BGA usually degrades and needs to be replaced.

http://www.coppelltvrepair.com/p/162...ausylhr-led-tv

So do you re-flow the processor? Or do you have to replace them typically? Never dealt with BGA stuff yet ...

Cheers! (potentially picking up one of these with similar symptoms). Was thinking LED Backlights and first so glad I did some research!