LG 55LB5900 Totally Dead!

[jason123]

Hi folks,

Got this LG 55LB5900 TV that's totally dead. I thought backlight as always, but no display with flashlight.

Took it apart and everything seems in order, visibly, no Power to the main board it seems. Can someone help me identify which is the Standby voltage on the connector? The power supply connector is labeled as shown in images, however no Standby. Is the PWR_ON or DRY_ON it? it's a 2-row connector so tricky to measure the DRY_ON, but PWR_ON has nothing.

Anyone has a schematic for this power supply, assuming it's what's bad?
Power supply board is EAX65423801 63072101

Measured the ceramic resistors and rectangular caps that I've seen go out in the past, and they check out. Checked all Transistors and Diodes, and none seem shorted. Fuses are ok on the power board. Any help is appreciated.


Thank you

[vinceroger69]

Re: LG 55LB5900 Totally Dead!

what voltage do you get across the large capacitor laid on its side on the hot side of the psu

[jason123]

Re: LG 55LB5900 Totally Dead!

106.9 v

[SLK001]

Re: LG 55LB5900 Totally Dead!

106.9 v

Then your boost circuit probably has a diode bad. Measure the diodes. Your voltage should be over 300V

[jason123]

Re: LG 55LB5900 Totally Dead!

My Apologies.. I was reading from cap to Chassis - Across cap it about 160 V DC
Is that still too low?

Anyone has a Schematic for this board and willing to share?
I'd hate to buy a Power card and find it's something else. Thanks again

[budm]

Re: LG 55LB5900 Totally Dead!

https://www.badcaps.net/forum/attach...8&d=1531074829
Picture is way out of focus to read the pinout of the connector that goes to the main board.
You can probe the pins of the connector from the wire entrance side of the connector using skinny probe.

[jason123]

Re: LG 55LB5900 Totally Dead!

Sorry about that.. i took a better pic but never uploaded

[jason123]

Re: LG 55LB5900 Totally Dead!

Only one showing life is the 12v reads 0.9 V

[R_J]

Re: LG 55LB5900 Totally Dead!

In case you don't want to repair it, shopjimmy lists this power supply for $39.00

[budm]

Re: LG 55LB5900 Totally Dead!

3.5V is the standby power supply. The switched 12V and switched 24V will not be present until PWR-ON control signal is present. So are you 100% sure that you count the pins correctly?
You can try repairing the board by troubleshooting down to component level or get the replacement board.

[jason123]

Re: LG 55LB5900 Totally Dead!

Thank you.. yes PWR_ON is the first pin and it's 0
Zero V. I ordered a board but would live to repair this for the fun of it. Any guidance o how to proceed without schematic? Tested all fuses, FETs and diodes. Measured resistance and capacitance on many parts and nothing obvioysly damaged.

[jason123]

Re: LG 55LB5900 Totally Dead!

I've attempted to find schematics for this board, but it seems most are viruses. Any hints or tips on what typically goes wrong on these power supply boards when there are no rails on the board, or when the voltage out of the Cap is lower than suggested?
Thanks

[budm]

Re: LG 55LB5900 Totally Dead!

You can test the power supply board by itself without having connecting to other board.
Put Black probe of the dcV meter on the negative leg of the main filter cap C610, then use the red probe on each end of the fuse F101 to see if you do have about 160Vdc on each end of the fuse with ref. to the negative leg of C610.
Pictures provided by shopjimmy.

[jason123]

Re: LG 55LB5900 Totally Dead!

Hi budm... yes i am getting 160v
Both fuses are good. I just done get any of the lower regulated voltages like the 3.5v or 5. No stanby.

On a different front, batteling with a Panasonic that i would appreciate your help on. Could you please take a look? https://www.badcaps.net/forum/showthread.php?t=70332

[budm]

Re: LG 55LB5900 Totally Dead!

You need to get the P/N of that 16-pin SMD SMPS IC in the hot side to find out if it has VCC for it to run or not.

[Andrew F. Ali]

Re: LG 55LB5900 Totally Dead!

you need to get the p/n of that 16-pin smd smps ic in the hot side to find out if it has vcc for it to run or not.

+110

[jason123]

Re: LG 55LB5900 Totally Dead!

The IC has "Fe" as marking, then number 6N143AA then 6A01

Assuming part number is 6N143AA.. I can't seem to find any datasheet on it.
Pin 8 has 52V, Pin 7, 5 and a couple others have 51.x V
Pin 9 through 16 have no voltage (few mV on some)

[vinceroger69]

Re: LG 55LB5900 Totally Dead!

ignore wrong ic data sheet

[budm]

Re: LG 55LB5900 Totally Dead!

FUJI: FA6A01
https://cdn.badcaps-static.com/pdfs/...dc74a503b7.pdf

Based on your Voltage reading: it looks like you use the wrong GND for your meter, you are making Voltage measurement in the hot side so you cannot use the chassis GND for your meter, you need to use negative leg of the main filter cap as you gnd point for the hot side of the circuit.
You need to report Voltage readings of all the pins, except GND pin.

[jason123]

Re: LG 55LB5900 Totally Dead!

pin voltage
1 57.3
2 .055
3 .075
4 .061
5 .22
6 0.000
7 0.000
8 0.000
9 0.000
10 0.030
11 0.000
12 0.000
13 0.222
14 0.05
15 0.05
16 0.05