Repairing a LG W2343T Monitor.

[MadJackTheFirst]

Hello everyone, first time here and first post.

I have an old monitor that I repaired in the past, replaced several capacitors, but now I'm facing a problem I do not know how to diagnose, much less fix. Although, truth be told, I have tried. Unsuccessfully.

The monitor, after being turned on (and connected to the video card), will, after about a second, emit a high pitch noise and then will turn black. If I turned it off and on, the same thing happens; it does not stay off for X time.

At first, when the behavior started, simply toggling on/off would fix it, but now that, obviously, does not work anymore.

What I have done so far:

I thought the INVERTER TRANSFORMER had died and replaced it (the noise seemed to come from it), but to no avail. The result remained the exact same.
I then bought a new replacement POWER BOARD for the monitor. Unfortunately, there was no change.

At this point I would like to be able to diagnose where the problem comes from and try to come up with a working solution. I am not sure if I will repair it in the end because I am starting to see that it might be more sensible to buy a new monitor as they are fairly inexpensive.

So, what would be the culprit? What could emit a high-pitched noise after it had warmed up a bit?

I can provide pictures or more information as needed.

Thank you.

 

[NsrMagazin]

The problem is only getting bigger. With every next turn you risk burning it completely.

There might be a short, check if the connectors have bend pins. These monitors should have only 1 or 2 PCBs at the back.

The problem does not seem to be from the power supply. Maybe in the video chip. It would be good to measure the chip pins voltage with and without the problem.

The sound certainly comes from the buzzer inside, what overloads the buzzer I don't know. You have a problem with both the video and audio channel for some reason they seem to receive more voltage or current then they should. Can you connect them to a different notebook and check if the result is the same. Start by tracing the buzzer on the PCB to the source(laptop).

Can be a settings problem.

They look expensive to me.

 

[Nigel Goodwin]

Probably the LCD panel faulty, and most probably a backlight problem inside it (either CCFL or LED failure depending on type).

 

[MadJackTheFirst]

The problem is only getting bigger. With every next turn you risk burning it completely.

Bigger how? I changed 4 capacitors and 2 years after this. Honestly I don't care if it burns out completely. I'd rather repair it if I can; at low cost, but it has served me well for almost 10 years.

There might be a short, check if the connectors have bend pins. These monitors should have only 1 or 2 PCBs at the back.

Extremely unlikely as this started suddenly. Pins don't usually bend on their own.

The sound certainly comes from the buzzer inside, what overloads the buzzer I don't know. You have a problem with both the video and audio channel for some reason they seem to receive more voltage or current then they should.

Buzzer? There's no buzzer or speakers on this monitor.

 

[MadJackTheFirst]

Probably the LCD panel faulty, and most probably a backlight problem inside it (either CCFL or LED failure depending on type).

Okay. What would be the steps to diagnose this? I have been thinking it might be the LCD display itself or one of the light. I have no idea how I could determine what is faulty.

 

[Nigel Goodwin]

Do you have a service manual for the monitor?, that might give you some ideas - apart from that the best way is to replace the LCD panel with a known working one.

Is it LCD or CCFL, certainly with CCFL most LCD's will shut the inverter down if any of the CCFL tubes aren't working properly, you could check the protection line going to the inverter - if you have the manual to show where it is.

 

[MadJackTheFirst]

While I looked for an answer I found a place that had the technical (repair) manual for the monitor. But the damn thing was so shrunk down that I could barely read anything. You could buy it though *roll eyes*...

Thanks for your answer. I'll give some thought to this.

 

[NsrMagazin]

I don't do this to receive negative attitude replies! If you don't want my help so be it!

 

[MadJackTheFirst]

I don't do this to receive negative attitude replies! If you don't want my help so be it!

Wow... Oooooooookay.

 

[LandonRobinson]

Hello everyone, first time here and first post.

I have an old monitor that I repaired in the past, replaced several capacitors, but now I'm facing a problem I do not know how to diagnose, much less fix. Although, truth be told, I have tried. Unsuccessfully.

The monitor, after being turned on (and connected to the video card), will, after about a second, emit a high pitch noise and then will turn black. If I turned it off and on, the same thing happens; it does not stay off for X time.

At first, when the behavior started, simply toggling on/off would fix it, but now that, obviously, does not work anymore.

What I have done so far:

I thought the INVERTER TRANSFORMER had died and replaced it (the noise seemed to come from it), but to no avail. The result remained the exact same.
I then bought a new replacement POWER BOARD for the monitor. Unfortunately, there was no change.

At this point I would like to be able to diagnose where the problem comes from and try to come up with a working solution. I am not sure if I will repair it in the end because I am starting to see that it might be more sensible to buy a new monitor as they are fairly inexpensive.

So, what would be the culprit? What could emit a high-pitched noise after it had warmed up a bit?

I can provide pictures or more information as needed.

Thank you.

High pitched buzzing/whistling usually means that an amplifier of some kind is no longer amplifying and as gone into "Oscillator Mode" and is literally making something vibrate to the point that it is producing noise, its hard to say what might be causing it, a short in a transformer's windings, a shorted resistor, a bad capacitor would do it.

A bad capacitor (due to their given life span) is where I would start, its the usual suspect in most amplification circuits.