LG 32LD450 shuts off after 15-25 seconds

[budm]

Re: LG 32LD450 shuts off after 15-25 seconds

to get this straight. Since you have the psu "hardwired" everything is ok?

+1

[MisterD]

Re: LG 32LD450 shuts off after 15-25 seconds

Not sure what I did but whatever it was is the reason the backlight stayed on during the last forced on of the power supply because now the tv has stayed on over 1 hour and 25mins without fail.
1. I removed and inspected the power supply board and re-installed it and tightened down ground/mounting screws. 2. Had my volt meter on the 20v range while hooked up across one of the main caps, I forgot to switch it back to HV range before turning on the tv, fried the meter( a cheap one)

3. Completely removed the wire harness that goes from main board to PS to seat 1k resistor in place in connector to jump 3.5v to Inv on/off for testing. 4.Removed test equip,re-assembled and tested the TV with the back on.
I'm not sure if the PS wasn't grounded good or if was a bad connection at Inv on/off since the backlights would either flicker or flash off/on 3 to 4 times prior to the tv shutting down.

[MisterD]

Re: LG 32LD450 shuts off after 15-25 seconds

Bud, if the Inv on/off lost voltage to that connection only at the connector on the PS rail would that cause the TV to shut down like this one was doing?

Thanks for the help to all, I appreciate it.

[budm]

Re: LG 32LD450 shuts off after 15-25 seconds

Bud, if the Inv on/off lost voltage to that connection only at the connector on the PS rail would that cause the TV to shut down like this one was doing?

Thanks for the help to all, I appreciate it.

The INV_ON signal is sepearated from the PS-ON (PWR-ON) signal, it seems to me that you lost both the PS-ON and INV-ON, isn't that correct.
Since you can force on the power supply and backlights and the TV keeps on working with that setup then that just about eliminates the power supply and backlights inverter problem.

[MisterD]

Re: LG 32LD450 shuts off after 15-25 seconds

Yes I lost both PS-on and Inv-on, but now after removing and reinstalling the PS board the tv is working normally, I have removed the resistor and battery, so I'm not forcing on the PS now but tv works like it should, has been on for 2 1/2 hours now.
Not sure what I did that fixed it. Could loose ground/mounting screws on PS board be possible?

[budm]

Re: LG 32LD450 shuts off after 15-25 seconds

May be loose Ground of the circuit board mounting holes which are also used for Grounding the boards to the chassis, I hope that was it.

[MisterD]

Re: LG 32LD450 shuts off after 15-25 seconds

If you look at post 4 at the PS picture you will see that there are four mounting screws but 3 of them are black and one is chrome, there are 2 flat ground tabs on top of the board as well as the solder type ones on the back of the board.
I put the chrome screw in the bottom right just as it was before I removed the board, the bottom left screw is marked black on the circuit board but both top and bottom right have the flat chrome tabs, I'm wondering if someone else has worked on this tv sometime and used coated black screws where they should be chrome to make good ground connections at the flat tabs.

[MisterD]

Re: LG 32LD450 shuts off after 15-25 seconds

The power supply/inverter board mounting screws were loose and I believe by tightening them down I have resolved the problem, left this tv on for 5 hours yesterday and 3 hours today with no failure.
Since the backlights either flickered or went off and back on a few times right before the tv shut down, I think the inverter circuit having a poor ground (due to the loose screws)was the cause.