LG 42LV 4400 Will not come on

[davg]

Re: LG 42LV 4400 Will not come on

Tks appreciate your advise. With the power button pressed I read 0.48v which I believe is 0 volts this is the same as just plugged in and sitting in standby.

[budm]

Re: LG 42LV 4400 Will not come on

So the PS-ON is present but basically no VCC to run the PFC IC, so you will need to dig deeper down to component level by tracing out the board to locate the switched Transistor that supplies the VCC to run the PFC IC. It is not going to be easy but can be done, it is a matter of tracing the VCC pin back to the switched Voltage source.

[budm]

Re: LG 42LV 4400 Will not come on

Parts for your TV:
http://www.shopjimmy.com/catalogsear...q=LG+42LV+4400

EEPROM:
http://www.shopjimmy.com/lg-42lv4400...eprom-only.htm
http://www.shopjimmy.com/lg-cov31310...2lv4400-ua.htm

You may have problem with two boards.

[davg]

Re: LG 42LV 4400 Will not come on

Ya I am kinda rusty at this been several years since I've done this. I was looking for a schematic of the board but nothing so far.
This problem seemed intermittent; my friend who owned the TV had the problem had it setting in the original box for about a year gave it to me to check it out when I got it home plugged it in it worked fine for a whole day before the condition came back. I turned it on and off several times then left it powered on for approx. 6 hrs when I turned it off for the night the next morning it would not power on???

[davg]

Re: LG 42LV 4400 Will not come on

Tks for the source but I do believe shopjimmy will not ship to Canada but I did source a used board on ebay

[davg]

Re: LG 42LV 4400 Will not come on

So the PS-ON is present but basically no VCC to run the PFC IC, so you will need to dig deeper down to component level by tracing out the board to locate the switched Transistor that supplies the VCC to run the PFC IC. It is not going to be easy but can be done, it is a matter of tracing the VCC pin back to the switched Voltage source.

Will that switched transistor be located on the main power board or the logic board? should I have any other voltages present on the main board connector when the board is powered on in standby or just the 5 vdc present

[budm]

Re: LG 42LV 4400 Will not come on

That switched transistor will be on the power supply board. Right now the power supply board is getting the PS-ON fine, it is the power supply board that is not working.

[davg]

Re: LG 42LV 4400 Will not come on

Tks Budm truly appreciate it and since my skills are lacking and I can buy a replacement board for 60 bucks its a no brainer just wanted to make sure I was replacing the right board

[davg]

Re: LG 42LV 4400 Will not come on

That switched transistor will be on the power supply board. Right now the power supply board is getting the PS-ON fine, it is the power supply board that is not working.

Tks Budm just received the replacement board but the symptoms are the same have 5.2v stand-by power but still will not power on? Unless the two boards has the same defect leads me to think the problem must be elsewhere?

[budm]

Re: LG 42LV 4400 Will not come on

Tks Budm just received the replacement board but the symptoms are the same have 5.2v stand-by power but still will not power on? Unless the two boards has the same defect leads me to think the problem must be elsewhere?

So the new power supply board with PS-ON forced on and still no PFC Boosted Voltage? If that is the case then your new power supply board is bad, you need to have that boosted Voltage when PS-ON is present.

[Andrew F. Ali]

Re: LG 42LV 4400 Will not come on

Disconnect the connector going from the PSU to the Main Bd. I couldn't make out the pin Nos. from the poor quality pics you posted. Anyway, you would need two (2) 1k Ohm resistors. Connect one end of a 1k Ohm resistor on the pin labeled Std-By and the other end to the pin labeled PS-ON. Plug the PSU into the ac. Measure the other pin and see if the voltages labeled on the connector appear. If they don't then the PSU is no good. If they do, leaving the 1st resistor in place, connect the other 1k Ohm resistor on the Std-By pin and BL-ON pin. Connect the backlights and apply the ac. The backlights should come ON and stay ON. If it does that then the PSU is perfect if it doesn't then the PSU/Inv Driver has a problem.

[davg]

Re: LG 42LV 4400 Will not come on

So the new power supply board with PS-ON forced on and still no PFC Boosted Voltage? If that is the case then your new power supply board is bad, you need to have that boosted Voltage when PS-ON is present.

That is quite possible since it is a used board?

[davg]

Re: LG 42LV 4400 Will not come on

Thank you Andrew sorry for the poor quality photo maybe this one will be better it shows the connector from the power supply to the main board. The pins are 1,2,3,- 5.1vsb (Remote_ on/off), 4,5,6,7 are ground, 8 & 9 - 12.6v, 10 - pwm1, 11 - pwm2, & 12 - pwm3 (BL_ on/off.
Not sure which pins are Std-By and PS-ON

[davg]

Re: LG 42LV 4400 Will not come on

Sorry I am not sure if I am reading the markings on this connector correctly?? I think the pins should be as follows; 1,2 Remote_ on/off, 3- 5.1VSB, 4,5,6,7 SGND, 8 & 9 - 12.6v, 10,11 BL_ON/OFF, 12 PWM1, 13 PWM2, 14 PWM3

[budm]

Re: LG 42LV 4400 Will not come on

DELTA DPS-131BP
LG COV31149501 (0500-0607-0240) Power Supply for 42LV4400-UA
Pictures provided by shopjimmy.

Pin 10 is the REMOTE ON/OFF (PS-ON) as printed on the board '(CN201 - 10) REMOTE_ON/OFF.
So the report on post #5 is not correct.

[davg]

Re: LG 42LV 4400 Will not come on

DELTA DPS-131BP
LG COV31149501 (0500-0607-0240) Power Supply for 42LV4400-UA
Pictures provided by shopjimmy.

Pin 10 is the REMOTE ON/OFF (PS-ON) as printed on the board '(CN201 - 10) REMOTE_ON/OFF.
So the report on post #5 is not correct.

Thanks for clearing that up Budm so pins 1,2,3 are common 5.1 VSB. That means I do not have the 5 VSB on pin 10 ps-on? And there is still no voltage when the switch is activated

[davg]

Re: LG 42LV 4400 Will not come on

Disconnect the connector going from the PSU to the Main Bd. I couldn't make out the pin Nos. from the poor quality pics you posted. Anyway, you would need two (2) 1k Ohm resistors. Connect one end of a 1k Ohm resistor on the pin labeled Std-By and the other end to the pin labeled PS-ON. Plug the PSU into the ac. Measure the other pin and see if the voltages labeled on the connector appear. If they don't then the PSU is no good. If they do, leaving the 1st resistor in place, connect the other 1k Ohm resistor on the Std-By pin and BL-ON pin. Connect the backlights and apply the ac. The backlights should come ON and stay ON. If it does that then the PSU is perfect if it doesn't then the PSU/Inv Driver has a problem.

Following your instructions I do get 12v and the backlights will come on and stay on? so the PSU/Inver Driver test ok??

[davg]

Re: LG 42LV 4400 Will not come on

So the main logic board is not switching the 5vdc to the ps-on pin. Reading the troubleshooting guide would seem to indicate a bad switching transistor? What are the probable causes

[davg]

Re: LG 42LV 4400 Will not come on

DELTA DPS-131BP
LG COV31149501 (0500-0607-0240) Power Supply for 42LV4400-UA
Pictures provided by shopjimmy.

Pin 10 is the REMOTE ON/OFF (PS-ON) as printed on the board '(CN201 - 10) REMOTE_ON/OFF.
So the report on post #5 is not correct.

Maybe I should start a new tread since some of the info I gave is incorrect? However the symptoms are the same the unite will not power on. I have the red indicator light on the front, I have 5vdc standby power but I do not have the 5 vdc at the PS-ON #10 pin when the power button is activated (or should I have it always)? The power supply board tested ok with the 1K resister from standby pin to PS-ON pin and the backlights came on and stays on with the extra 1k Resister from standby to BL-ON pin. What would happen if I placed the 1K resister form SBP to PS-ON Pin with both boards connected? What should I look for that would cause the logic board not to switch the 5 vdc? or is the 5 vdc switched by activating the power on switch or the remote on switch. Where can I read to get more understanding of this process? I apologize if these are stupid questions but I am a learner with lots to learn and would take a lot of satisfaction from this to make it work.

[budm]

Re: LG 42LV 4400 Will not come on

Right now the problem is on the main board, what the exact cause for it not to send PS-ON (<1Vdc = OFF, >2Vdc = ON) I do not know. You may try heating and cooling the main board to see if the PS-ON will be present or not.