LG 47LS4500-UD No Power

[D_orr4]

Hey folks,

I have an LG tv (47LS4500-UD) that wont turn on. There is no picture, sound or stand by light when plugged in. From reading other posts with similar problems, it sounds like the culprit may be a dead Main Board. I'm new to electronics but after reading these posts I decided to take the back off and due some voltage checks. I'm getting good stand by voltage on the power supply, but hitting the power button on the tv doesn't change anything across the pins on P201. I also read that on this model of tv there is a certain capacitor (C603)and diode (D607) that often fail. Both of these seem to be operating. Am i right to assume I need a new Main, or is there something I'm missing?

thanks
D

[budm]

Re: LG 47LS4500-UD No Power

If you upload good clear pictures of the whole backside of the TV showing all the boards, and then the straight shot pictures of the top and bottom side of the power supply board the you will get a lot more help, right now we have no idea what we are dealing with and without having the set in front of us to look at make difficult to help. The more details you provide the better.

[D_orr4]

Re: LG 47LS4500-UD No Power

Here we go. let me know if any additional pictures will help out. thanks!

[budm]

Re: LG 47LS4500-UD No Power

https://www.badcaps.net/forum/attach...2&d=1522858799

'I'm getting good stand by voltage on the power supply, but hitting the power button on the tv doesn't change anything across the pins on P201.'
So on that connector P201 all the pins show 0 Volt except the 3.5V pins or you are getting Voltages but we do not know what you are getting?

[D_orr4]

Re: LG 47LS4500-UD No Power

All the pins show 0 volts except the 3.5v pins.

[Andrew F. Ali]

Re: LG 47LS4500-UD No Power

Remove the connector P201 from PSU to Main Bd. Plug the TV into the 120Vac and see if the backlights turn ON. If NO then the PSU may not have the 'pull-up' resistors. With the ac OFF and P201 removed, connect a 1k resistor across the 3.5V and PWR-ON pins. Connect the ac and measure wrt GND the 24V and 12V pins to see if you have powered the PSU. If NO then PSU BAD. If YES then disconnect ac and connect another 1k resistor across 3.5V and the DRV-ON pins (leaving the 1st resistor in place). With the LED connector in place, connect the ac and see if the backlights turn ON. If NO then PSU BAD or Backlights bad. If YES then PSU GOOD. Problem is definitely Main Bd.

[D_orr4]

Re: LG 47LS4500-UD No Power

thanks very much for the help. I'll hopefully have some time this weekend to work on it and reports back. much appreciated.

[D_orr4]

Re: LG 47LS4500-UD No Power

Hey guys, so after finally tracking down the only electronics store in my small city I went to pick up some 1k resistors. Long story short, the old curmudgeon store employee would not sell me any resistors as it would be a waste of my money. He insisted my problem was bad capacitors on the power supply. He advised me to change all the capacitors and could almost guarantee this would resolve the problem. I'm not convinced,
based on what I've read regarding these tvs.

Im now looking to order some resistors or perhaps capacitors off of ebay or amazon. My question now is, is there anyway to tell the quality of products that I'm ordering? I don't want to replace inferior parts with equally cheap parts that will fail again in a year or two.

thanks

[ngth82]

Re: LG 47LS4500-UD No Power

Wait. Stop.

See Post #6 again. Andrew is asking you to remove the power cable between the main board and the power board. Disconnect it on the main board side.

Use a 1kohm resistor between the 3.5V pin and the "PWR_ON" or PS_ON pin. This will force the power supply board to turn on. Measure the power board for +12 and +24 being generated at the cable.

This is just a buck or two for a pack of through hole resistors. No need to jump the gun and resort to swapping out caps yet.