LG 42LV 4400 Will not come on

[davg]

My LG42LV4400 TV will not come on? The red light on the front is on when plugged in but do not change when the power on button is pressed or the power-on on the remote is pressed. Yesterday was fine turned it off with the remote last night and it hasn't come on since. I did pull the back off it to check for swollen caps but none seen. I did check a couple of voltages on the power supply board @ CN201 and found that I have 5v standby but no 12v. Should 12V be present there before being turned on.

[dick_barton]

Re: LG 42LV 4400 Will not come on

You really need to give the pinout number, name and voltage for the connector in the red box.

[davg]

Re: LG 42LV 4400 Will not come on

This might be a little better image

[budm]

Re: LG 42LV 4400 Will not come on

Please report the Voltage for all those pins except GND pin as request in post #2
You MUST put down the pin name and follow by the Voltage reading for eack pin when TV is off and when the power switch is activated so we can easily see what it has and does not have in two states.

[davg]

Re: LG 42LV 4400 Will not come on

Pins 1,2,3 from the bottom is Remote on\off and I am reading 5.2v Pins 4,5,6,7 is SGND Pins 8 &9 is 12.6v and I am reading 0 voltage. Pins 10,11,12 are labeled PWM 1 PWM 2 & PWM 3 BL on\off and I am reading 0 voltage. The unit do not power on.

[davg]

Re: LG 42LV 4400 Will not come on

I am Sorry but forgot to thank you guys for your response

[nomoresonys]

Re: LG 42LV 4400 Will not come on

Looking like bad mainboard.

[budm]

Re: LG 42LV 4400 Will not come on

Pins 1,2,3 from the bottom is Remote on\off and I am reading 5.2v Pins 4,5,6,7 is SGND Pins 8 &9 is 12.6v and I am reading 0 voltage. Pins 10,11,12 are labeled PWM 1 PWM 2 & PWM 3 BL on\off and I am reading 0 voltage. The unit do not power on.

So you do have PS-ON (Remote on\off) to turn on the switched 12V but it is not coming on.
Please check the DC Voltage right between the two legs of the main filter cap in the HOT side of the circuit, it should be around 380 ~ 400VDC range.
Power supply: Delta DPS-131BP A

[davg]

Re: LG 42LV 4400 Will not come on

Tks budm voltage across c800B is 168 vdc rather low voltage I am not at all sure how that circuit works

[budm]

Re: LG 42LV 4400 Will not come on

Well, that means the PFC Voltage booster circuit is not working, that 12V and the LED power supply section needs that Booted Voltage to run.
There are 3 barrel body type Diodes D800A, 800B, 801 close by the main filter cap, check the RESISTANCE in both directions on all 3 of them and report the readings.

[davg]

Re: LG 42LV 4400 Will not come on

Tks again budm D801 is showing 0 ohms in one direction and 0L in other direction D800A D800B is showing 0L in both directions without any power supplied. With unit plugged in D800A & B is showing 10.9 m oms in one direction and 0 Ohms in the other direction where as 801 is showing 0L one direction and 0 ohms in the other

[budm]

Re: LG 42LV 4400 Will not come on

What Ohm scale are you using?
Remove D801 and test it off the board.

[davg]

Re: LG 42LV 4400 Will not come on

Auto scale with the scale set to ohms 800A & B is showing 0L both directions whereas 801 is showing 0L in one direction and 0 ohms in the other. Not quite setup right now to pull 801 maybe tomorrow

[budm]

Re: LG 42LV 4400 Will not come on

Use 200 Ohms scale on that D801, but at this point I doubt that 801 is bad otherwise it would have shown <1000 Ohms in BOTH directions.
What we to do next is to check VCC pin of the PFC Controller IC to see if it has switched DCV on the VCC pin to run.

[davg]

Re: LG 42LV 4400 Will not come on

Are we talking IC 901 you will have to walk me through that one? Don't have a schematic

[budm]

Re: LG 42LV 4400 Will not come on

https://www.badcaps.net/forum/attach...7&d=1528048318
Looking at your pictures which are not very clear, it looks like 8-PIN SMD IC801 to the left of D801.

[davg]

Re: LG 42LV 4400 Will not come on

Yes that is correct # 1608B PJVG

[budm]

Re: LG 42LV 4400 Will not come on

NCP1608 PFC Controller by ON Semi.
Check and see if you do have Voltage between VCC and GND PIN or not when TV is turned on. Be real careful since you are working in the deadly side of the circuit.

[davg]

Re: LG 42LV 4400 Will not come on

Tks budm as indicated in my first post the TV do not turn on? So i can only test with it plugged in and there is no voltage between 6 & 8 on that IC

[budm]

Re: LG 42LV 4400 Will not come on

It does not matter if the TV comes on or not, we are looking to know if the Voltage changes or not when power switch power switch is activated.
"Remote on\off and I am reading 5.2v" right now the power supply is getting the control Voltage to turn on the rest pf the power supply but it is NOt happening right now so you need to fix the power supply problem first before anything else.
You should read the basic troubleshooting first so you will understand how the TV works.