LG Flatron L2010P no picture

[DPyro]

Hi everyone, I'm new here and am hoping you can help me with my problem. I recently acquired an LG Flatron L2010P LCD for free and am looking to repair it. The problem with it is there is no picture and no OSD, however the backlight works and the power indicator light works. I have pulled the monitor apart and looking at the power supply, there is no visual bulging from the capacitors except for the large 400v 150uf which I'm guessing could be the problem.

Attached is a top and bottom view of the board.

[Rtech]

Re: LG Flatron L2010P no picture

What is the DC Voltage across the big cap...I'm presuming you have a Meter, and please note you are probably looking at approx 165volts DC, as the Mains in Canada is 110volts AC ??? dont be confused,the Dc should be about 1.414 of the AC.

[imp]

Re: LG Flatron L2010P no picture

Please press the top of the large capacitor to see if the plastic disc seems "tense" or if it easily goes flat.

[DPyro]

Re: LG Flatron L2010P no picture

The mains in Canada is 120v. Sorry I don't have a multimeter at the moment (which is a good brand?).

EDIT: The large capacitor is hard as a rock.

[imp]

Re: LG Flatron L2010P no picture

The mains in Canada is 120v. Sorry I don't have a multimeter at the moment (which is a good brand?).

EDIT: The large capacitor is hard as a rock.

To measure a simple DC you can use almost any multimeter ... I personally prefer Fluke but for average Joe perhaps they are a bit to expensive. I´m sure someone in this forum can recommend a decent multimeter to you available in your region.

If the plastic disc can´t be suppressed the top of the capacitor is likely bulged. To be 100% sure you can easily cut the plastic film in the capacitor to remove the disc. I you do so, make sure the capacitor is discharged first (even though it may be broken). And post a new picture of it as well

[DPyro]

Re: LG Flatron L2010P no picture

To measure a simple DC you can use almost any multimeter ... I personally prefer Fluke but for average Joe perhaps they are a bit to expensive. I´m sure someone in this forum can recommend a decent multimeter to you available in your region.

If the plastic disc can´t be suppressed the top of the capacitor is likely bulged. To be 100% sure you can easily cut the plastic film in the capacitor to remove the disc. I you do so, make sure the capacitor is discharged first (even though it may be broken). And post a new picture of it as well

What is the proper procedure to discharge a 400v capacitor (without getting zapped)?

[imp]

Re: LG Flatron L2010P no picture

I usually discharge them with my multimeter be simply measuring the voltage and watch it decrease ... You can use almost anything with some resistance in it (for example a light bulb), or if don´t mind seeing a spark, short it with a screwdriver. It´s not nice but it gets the job done.

[DPyro]

Re: LG Flatron L2010P no picture

I usually discharge them with my multimeter be simply measuring the voltage and watch it decrease ... You can use almost anything with some resistance in it (for example a light bulb), or if don´t mind seeing a spark, short it with a screwdriver. It´s not nice but it gets the job done.

By shorting it with a screw driver does that not damage the board if it's still soldered to it?

[imp]

Re: LG Flatron L2010P no picture

No. The spark doesn´t have that energy, besides, the spark is created exactly where you place the screwdriver (i.e. on the top of the capacitor's "legs"). The copper tracing on the circuit board is never involved. IF the capacitor is faulty you won´t even have any energy to discharge, this is just a precaution.

[DPyro]

Re: LG Flatron L2010P no picture

Ok, I tried two old PCB's I made years ago. One is a roulette machine and the other is a circuit tester (red and green led to test + and -) both require a 9v battery. I connected them to the leads of the capacitor and neither had any charge. Tried the screwdriver to confirm the capacitor is fully discharged.

EDIT: Took the plastic off and I can't really tell if the capacitor is bulged.

[imp]

Re: LG Flatron L2010P no picture

Well, when I meant almost any resistance will do, perhaps I should have mentioned that if the capacitor was charged and had a couple och hundred volts on it, you shouldn´t use any sensitive equipment to discharge it with. Something that runs on a 9V battery doesn´t like to be feed with 200V, not even for millsecs... A light bulb is much more rugged.

The only thing more you can do now without a multimeter is to confirm that the large capacitor is broken/bulged and either change that one and try if it works, or change all the capacitors on the board while you´re at it. It will only cost you a few $ more and you don´t have to think about it again.

[imp]

Re: LG Flatron L2010P no picture

EDIT: Took the plastic off and I can't really tell if the capacitor is bulged.

Hmm, no it doesn´t. Too bad, otherwise this might have been an easy fix.

Next step is to measure voltages with the supply connected to mains. You must be really careful when working with live circuits and if you feel any discomfort in doing so, you should consider asking someone for practical help or just leave it. When working on hundreds of volts nasty stuff can happen even to the most experienced.

Buy yourself a decent multimeter if you choose to continue with this monitor

[DPyro]

Re: LG Flatron L2010P no picture

Is it possible this could be an even easier fix than I thought and just be a video cable that needs to be replaced from the main board? Obviously if the backlight lights up the inverter should be good, it's just not sending a video signal to the LCD?

EDIT: Found another thread with a similar problem.

I also think I found the service manual for the mainboard.

[retiredcaps]

Re: LG Flatron L2010P no picture

The problem with it is there is no picture and no OSD, however the backlight works and the power indicator light works.

1) Your big cap is likely working 100% because you get a power LED and the backlights work. If your big cap was bad, you would not get either of the above.

2) If you get no picture, it could be a simple as a blown SMD fuse on the panel board. The panel board runs the length of the monitor and is located at the top of the lcd. You will need a multimeter to measure the fuse as you can't tell if it is good or bad by looking at it.

[DPyro]

Re: LG Flatron L2010P no picture

Ya I read that in the other thread. That would be a pain in the ass to access.

EDIT: Could you clarify what you mean by 'panel board'? I know there is the main board with the vga and dvi interface and there's another long stripe board to control the osd. If its underneath all that it will be a pain to take apart.

[budm]

Re: LG Flatron L2010P no picture

See picture.

[DPyro]

Re: LG Flatron L2010P no picture

I ordered a multimeter online so I'll update this post when I receive it.

[retiredcaps]

Re: LG Flatron L2010P no picture

I ordered a multimeter online so I'll update this post when I receive it.

Which did you get?

[tom66]

Re: LG Flatron L2010P no picture

The symptoms of a big cap failing are one or more of:
- All secondary caps bulging AND primary bulging (even if good brand)
- Flickering/intermittent backlight
- Buzzing/humming sound from PSU around 100-120Hz
- Diagonal or vertical noise on video like hum bars on old TVs (rare, but I suppose possible)
- Dim power LED (could also be other bad caps...)
- If it has speakers, humming or buzzing especially on louder sounds.

Additionally, if the monitor has PFC (voltage boosted to around 390V):
- Low voltage on big cap (around 200-300V instead of 400V)
- Loud clicking or popping from PSU intermittently, on LCD especially on darker scenes
- If no power (completely dead): Shorted MOSFET and/or diode on primary, blown fuse

The big cap filters the peaks between the mains voltage. If it fails, the monitor sort of runs out of power half way on each cycle, so the secondary caps take a lot of stress as they have to provide this. Usually they can't, this can cause the backlight to drop out (typically the first to go), then other stuff can go wrong.

A good power LED doesn't necessarily mean the big cap is OK.

[DPyro]

Re: LG Flatron L2010P no picture

Which did you get?

Range DC Current: 2000uA-10A ±(1.0%+2dgt)
Range Volts DC: 2000uA-10A ±(1.0%+2dgt)
Range Volts AC: 200-750V ±(1.2%+10dgt)
Resistance: 200O-2MO±(0.8%+2dgt)
Power Supply: 6F22 9V Battery
Temperature: -40°C ~ +1000°C ±(.75%+2dgt)
Size: 126 x 70 x 24mm/5.0 x 2.8 x 0.9in(L x W x H)