Newbie with LG 37LH5000 (PS?) problem.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

They are both voltage regulators and IC801 should have 3.3V output and IC803 should have 1.8V output. You need the set switched on and out of standby.

Is input from the computer through the HDMI cable the best way to achieve this, or do I just need the blue light showing rather than the red?
I'm not sure if the blue light will stay on for long if there's no audio/video input.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

They are both voltage regulators and IC801 should have 3.3V output and IC803 should have 1.8V output. You need the set switched on and out of standby.

Thanks.
Just off to get myself a multimeter and some crocodile clips.

[dskall]

Re: Newbie with LG 37LH5000 (PS?) problem.

I would then move to mainboard and heat it up. Then to t-con board.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

I would then move to mainboard and heat it up. Then to t-con board.

Thanks,
I'm in the process of doing that.
As I understand it, thanks to the help received here, in theory I can warm each board until there's a positive result, then, having located the problem board, selectively warm each part individually to home in on the failing component.
It's good for me to have such a relatively simple test procedure available.

I'm still unclear as to what factors, other than low temp at switch on and higher temp after 90 minutes of running might be responsible for the long delay before a good picture is displayed on the TV.

I understand that heat may cause contact in board circuitry to be remade where there is deterioration in the soldering. But what other than temperature might be causing the long delay?

Regards,

MickyLuv

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

They are both voltage regulators and IC801 should have 3.3V output and IC803 should have 1.8V output. You need the set switched on and out of standby.

Thanks Dick_Barton, for your detailed input.
I've bought a multi-meter and I'm just going to spend a while learning how to use it for the specific purposes you suggest.
I'd like to rush straight in for a bit of trial and error but the potential errors might make that a big mistake.

Regards,

MickyLuv

[dick_barton]

Re: Newbie with LG 37LH5000 (PS?) problem.

You need to set you meter to say 20V DC. With the black lead on the chassis use the red lead to test the legs of the IC's. Don't press too hard when using the red lead so as not to slip and short things out.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

Thanks for all the good advice. It's been a great help.
I'm going to run through all the suggested possibilities again to ensure I didn't miss anything important.

Before I do the testing of various components with the meter I'm going ro make a table-like cover to shield the other boards while I work on the selected board. I'm also going to make a small plastic shield to protect adjacent contacts on components from being shorted.

It's going to take me a little while to get familiar with the multi-meter too.

Because of a possible delay in my continuation of this thread, would it be better if future questions arising were put into a new thread/topic?

Can anyone tell me what the fourth board is, which I added a later photo of?
I cant seem to see an example of it in any of the YouTube tutorials and my search for service manuals or diagrams has had zero results so far.

Kind regards and thanks,

MickyLuv

[dick_barton]

Re: Newbie with LG 37LH5000 (PS?) problem.

Board4.jpg is an inverter board to dive the CCFL tubes (backlights)

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

They are both voltage regulators and IC801 should have 3.3V output and IC803 should have 1.8V output. You need the set switched on and out of standby.

I've only ever done board and card swap outs before, never any component testing, so it took me a bit of time to get this far.

Multi meter test showed:
IC801 = 3.311V output
IC803 = 1.811V output

So they seem to be OK.

==========

Is it possible to validate the overall state of the power supply board by
testing the output voltages from it to the main
board on the one side and the inverter board on the other, or is it more complicated than that?

Regards,

MickyLuv

[dick_barton]

Re: Newbie with LG 37LH5000 (PS?) problem.

Are these checked by testing the continuity?

They should read OL (open circuit) when checked with a multimeter but the way to test them is to check that they have not bulged at the top or show signs of the plastic sleeve splitting. Remove and measure with a capacitance meter and compare read value with written value. Lots of multimeter have this function but the real test is to check them using an ESR meter.
Without the tools the only way to be sure is to replace.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

They should read OL (open circuit) when checked with a multimeter but the way to test them is to check that they have not bulged at the top or show signs of the plastic sleeve splitting. Remove and measure with a capacitance meter and compare read value with written value. Lots of multimeter have this function but the real test is to check them using an ESR meter.
Without the tools the only way to be sure is to replace.

I see that several kits available for replacement seem to have just some of the electrolytic capacitors, rather than the full range of capacitors on the board.
Is this OK? Are the other capacitors on the board considered not to be a potential problem?

Regards,

MickyLuv

[dick_barton]

Re: Newbie with LG 37LH5000 (PS?) problem.

There's no guarantee that replacing the capacitors in the power supply will cure the fault but if the kit is cheap then it wouldn't hurt.

Unfortunately the fault has not been pinned down yet but normally heating and cooling components is the quickest way to find the faulty component(s)

Someone was using a funnel and hair dryer to focus the heat which can be more selective for heating individual components.

Edit
Do any of the voltages on the power supply change between switch on (cold) and when you have a good picture.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

There's no guarantee that replacing the capacitors in the power supply will cure the fault but if the kit is cheap then it wouldn't hurt.

Unfortunately the fault has not been pinned down yet but normally heating and cooling components is the quickest way to find the faulty component(s)

Someone was using a funnel and hair dryer to focus the heat which can be more selective for heating individual components.

Edit
Do any of the voltages on the power supply change between switch on (cold) and when you have a good picture.

I hope I'm not getting this wrong but my limited understanding is that each board would be heated overall with a hair dryer.
Then eventually the board with the fault would function properly after heating, so the TV would then perform correctly for a while.

Having identified the problem board by this method, then individual components on the various faulty board areas would be selectively heated to identify the faulty component more specifically.

If this is how it goes, then I cant get past the first part of the process, because after heating each board generally in turn, at no time has the TV shown any sign of overcoming the original problem.
So the first stage of the identification process is so far not completed.

=====

I haven't managed to do any readings of the voltages from the power supply yet. I have been trying to follow a YouTube tutorial on the process, where the board is left in place and the TV switched on and active. Then the red probe is pushed down the side of each mainboard wire into the connecting plug and the voltage reading of each line from the power supply board to the mainboard is taken. I don't think I can be doing this right because I'm getting no response on the meter. Just all zeros.

There is another tutorial on an alternative method with the board removed from the TV but powered on and the plugs for the lines to the mainboard removed from their sockets, Then the voltage of the pins in the power board sockets are tested. I'm going to try this next, if the first method doesn't come good after a couple more tries.

Regards,

MickyLuv

[dskall]

Re: Newbie with LG 37LH5000 (PS?) problem.

Unfortunately this is not an exact science. Trial and error. Have you also taken cover off t-con and heated and tested voltages on it? Could also be a panel issue. Try flexing panel a little see if it has effect.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

Unfortunately this is not an exact science. Trial and error. Have you also taken cover off t-con and heated and tested voltages on it? Could also be a panel issue. Try flexing panel a little see if it has effect.

All good advice.
Where trial and error is concerned, my main error so far is not being able to conduct specific trials to a conclusive point.
I appreciate your detailed advice and I'll carry out the test you describe in the way you describe them.
I'm still trying to test the power supply board and I'm not keen to move on to other areas until I've tested it effectively..
Is it really possible that the problem is in the panel, even if the display comes good after a long wait?

[vinceroger69]

Re: Newbie with LG 37LH5000 (PS?) problem.

Quote

I haven't managed to do any readings of the voltages from the power supply yet. I have been trying to follow a YouTube tutorial on the process, where the board is left in place and the TV switched on and active. Then the red probe is pushed down the side of each mainboard wire into the connecting plug and the voltage reading of each line from the power supply board to the mainboard is taken. I don't think I can be doing this right because I'm getting no response on the meter. Just all zeros.

So how are you testing the voltages? your multi meter should be on dc volts the black probe in held onto the metal tv chassis and then push the red probe down the side of the wire into the connector so the end of the probe touches the metal part of the wire connector you should then get a voltage reading ok but it depends on how big your probe tips are too, i have a set i have soldered a needle on too the positive tip so i can test the pins etc better.
https://www.youtube.com/watch?v=TELvc0thP34

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

Quote

So how are you testing the voltages? your multi meter should be on dc volts the black probe in held onto the metal tv chassis and then push the red probe down the side of the wire into the connector so the end of the probe touches the metal part of the wire connector you should then get a voltage reading ok but it depends on how big your probe tips are too, i have a set i have soldered a needle on too the positive tip so i can test the pins etc better.
https://www.youtube.com/watch?v=TELvc0thP34

I'm testing it exactly as you describe, except, as you mention, I seem to be having trouble getting the positive tip to reach metal.
I've tried a light touch and a somewhat heaver touch. I'm a bit reluctant to press harder, so I think I'd better try your needle method.

[vinceroger69]

Re: Newbie with LG 37LH5000 (PS?) problem.

can you upload a picture of your tv one showing how all the boards are connected together and one of each of the boards so we can see what type of connectors etc were dealing with.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

can you upload a picture of your tv one showing how all the boards are connected together and one of each of the boards so we can see what type of connectors etc were dealing with.

Yes, thanks, I'll gather them together in one post.

[MickyLuv]

Re: Newbie with LG 37LH5000 (PS?) problem.

Here's part of a flowchart for a similar LG model I found online.