LCD monitor problem

[undee.sun]

Hi guys,

I have problem with my LCD monitor LG 19". I just bought and use it for a month but then suddenly not working when I connect it to my laptop and my TV tuner. It is caused by a lightning, but fortunately it is only damage partially. If I connect it with my old PC desktop, it still works properly. I have tried to connect it with at least 3 another laptop and 2 another new PC desktop and I have tried to change the resolution and the frequency and also replace the cable but it could not work, it just stay on "safe mode". And weird when I connect it to the old PC desktop then it works fine.

I am wondering what is the difference between the output VGA from new PC and the old PC. I am just thinking that probably I can make some simple electronic schematic that could convert the output VGA signal from new laptop or TV tuner to be the same signal of the old PC desktop.
Please need your advice...

Regards,
-Andi.

 

[HiTech]

I'm wondering if your new laptop video signals are DVI type whereas the old PC is VGA? If so, that may be the case here.... the DVI circuitry happened to be affected from the lightning strike while the VGA made it through? Being only a month old, it should be under warranty so I try to get a replacement or repair under warranty before going further in fixing it yourself or bothering to build a circuit.

 

[undee.sun]

The DVI type should have different connector, right? it is the three row 15 pin for both the old and the new PC.
Yes it is under the warranty, but unfortunately I bought it from another country which is not worth it if I send it back to that country , the cost will be higher rather than I buy the new one in here.
And I have ever tried to bring it to the LG service center in my country, but they can not repair it, they told me that they need to replace the main board but the LCD type is different and there is no any replacement board in here.

 

[HiTech]

OK so you are saying your monitor has only the 15-pin sub-D VGA connector as shown at the bottom in the image? The connector shown at top of image is DVI.
**broken link removed**

Rethinking that you are connecting it to your laptop has me wondering if you have your laptop's VGA port enabled? It's either FUNCTION (key) + F4 or F5 or F7 or whatever your brand of laptop has it tied to. One of those function keys at the top of the keypad will toggle the VGA port on or off. Perhaps your laptop has reset itself to factory default which usually is: "internal diaplay only" You would need to toggle the respecting function key to "internal display & external display". Sometimes they are referred to as LCD/CRT on the function rown of keypad.

 

[undee.sun]

yes the monitor has only the VGA connector.
I have already tried and make sure about the thing that you concern. I also tried with an external TV tuner and a PC, and it didn't work. So I can make sure that the problem is on my LCD monitor.
Any other thought? how about the sync on green output signal from VGA, is it different between old VGA card and the new one? maybe the signal output of old VGA is sync on green but the new one is not, just my thought but I don't have much knowledge about this VGA signal.

 

[mdanh2002]

Hi,

Search for "vga monitor identification bits" such as this one VGA Monitor Identification Bits?. I think modern LCD monitor sends specific information via certain pins in the VGA cable to identify itself, such as manufacturer, size, supported resolutions, etc. Modern video cards may also be programmed to look for this information. If it was not found, no signal is sent and the LCD stays in standby mode. I realized this a few years back when I connected the VGA port of a laptop to my oscilloscope, only to find out that no signal was sent since an LCD monitor is not detected. I later managed to view the signal by using a pass through cable.

My guess is that some damages may have prevented the LCD from identifying itself, so it will only work with older VGA cards that do not expect any identification information from the monitor.

 

[undee.sun]

hi mdanh2002, thanks for the information. So because of the monitor could not give the identification bits, then the laptop is not giving the output signal into the monitor. I just found from another thread that we can simulate a monitor connected to the computer just using 75ohm resistor to ground on the RGB line. I am going to try it.

 

[mdanh2002]

hi mdanh2002, thanks for the information. So because of the monitor could not give the identification bits, then the laptop is not giving the output signal into the monitor. I just found from another thread that we can simulate a monitor connected to the computer just using 75ohm resistor to ground on the RGB line. I am going to try it.

Be careful that since the monitor is partially damaged, attempting to ground the RGB line via a resistor or any type of circuit connection may result in unexpected voltage which may "shock" the laptop VGA card and cause further damage. Do it with the monitor alone, then with an old graphics card, measure all voltages and see if they are within limits, before trying it on your laptop VGA port.

 

[undee.sun]

I have just tried it, but the resistor that I have only the 100ohm, and it doesn't work
The response become different : before adding the resistor, when it is not connect to anything, the monitor shown "searching the signal", then after connect it to the laptop, it become power saving mode. But after adding the resistor, it is always on the power saving mode either connect it to laptop or not.
Any thought ?

 

[blueroomelectronics]

Since it's only a month old either return it or get it fixed. It's got to have some sort of warranty.

 

[mdanh2002]

I think damages due to natural disasters (earthquake, lightning, ...) are not covered by warranty. That said, it all depends on the service person, he may just replace the set with no questions asked.

 

[Nigel Goodwin]

I think damages due to natural disasters (earthquake, lightning, ...) are not covered by warranty. That said, it all depends on the service person, he may just replace the set with no questions asked.

Obviously physical damage isn't covered by warranty - and if a lightning strike has left visible burns and destroyed components and copper track, then it would obviously be noticed and rejected. But if there's no visible signs, there's no evidence of a lightning strike, so should pass under warranty no problem.

 

[undee.sun]

Since it's only a month old either return it or get it fixed. It's got to have some sort of warranty.

As like on my earlier reply that I can not get the warranty

 

[mdanh2002]

Obviously physical damage isn't covered by warranty - and if a lightning strike has left visible burns and destroyed components and copper track, then it would obviously be noticed and rejected. But if there's no visible signs, there's no evidence of a lightning strike, so should pass under warranty no problem.

I think it's not possible for a lightning strike to damage an LCD partially (as described by the thread starter) and yet does not leave any trace. Some components on the PCB must have been burnt. But it's up to the service personnel to decide whether to open up the unit and investigate why it fails and whether the failure is under warranty or not, or just simply send a replacement to save time and efforts. The latter is quite come here in Singapore - as long as the unit does not have any damages visible to the naked eye, most companies will just approve the RMA request and send you a replacement. There's no point in spending another few hours to investigate the root cause, conclude that the warranty has been void, only to receive complaint from customer later on.

Once my hard disk was dropped on the flour while copying files, making it unusable. It was still detected by Windows, yet make loud noises when I tried to access it (symptoms of head crash). I sent for RMA and got a replacement 3 days later. I bet the serviceman did not bother to check why my hard disk fails.

 

[undee.sun]

The warranty problem is not because of the lightning that will leave any trace or the part that looks burnt. But the problem I bought it in another country and I can not warranty it in my country.
So if I can not repair the monitor then it become a junk, the only choice is repairing by myself. There is no any burnt on the PCB, all looks visibly good, probably just small damage inside the one of the IC. It works on the old PC, but I don't have the old PC, I just try it on my friend's old PC. And I need this monitor for my laptop and my external TV tuner.

The symptom is when I plug the VGA connector to my laptop then it will suddenly becomes on power saving mode. But if it does not connect to anything, it search for a signal (shown and written on the monitor : "searching cable signal")

How does the monitor become on power saving mode? Does it when there is no signal on RGB pin or probably there is one pin that used for making power saving mode?

 

[mdanh2002]

How does the monitor become on power saving mode? Does it when there is no signal on RGB pin or probably there is one pin that used for making power saving mode?

I think the monitor is sensing that a VGA cable has been connected, and it should look for a VGA signal. Either adding a resistor does not work with this monitor, or the monitor has been partially damaged and your modification confuses it further.

 

[undee.sun]

The power saving mode did happen from the first the monitor partially damage, not because of the modification.

For now I assume that :
1. the power saving mode is because the laptop does not give the signal to the monitor.
2. the laptop does not make any output signal because the laptop / VGA think that there is no any monitor attached.
3. the laptop/VGA think that there is no any monitor even it already connected because the monitor partially damage and could not give the monitor identification bits that the VGA asked.

So for repairing this monitor, I should make some circuit that able to simulate monitor connected to VGA or in other word should make the signal of identification bits that will be received by the VGA / laptop.
If there any other idea please tell me..

 

[undee.sun]

I just realize that actually the laptop has already detect the monitor, I can see it from the configuration for changing the output VGA. When I connect the monitor into the laptop, this configuration will be shown. And also I can use the button Fn+F8 when the monitor is connected to the laptop, but when the monitor is not connected then pressing the Fn+F8 will do nothing. So I don't think I need to simulate it.

I confuse now, what is the really difference between classic VGA card from old PC and the new VGA card from new PC / laptop ?

 

[killivolt]

Powered Splitter or KVM

You could try a KVM or Powered Splitter. Maybe the circuit could act like an Isolation Transformer while boosting the signal or balancing it.

Either one. Meanwhile if it is something to do with a weak analog signal issue. If you could find a VGA booster cheap on EBay or somewhere then see if that alters the signal to allow it to be process.

kv

Edit: I also would think that a leaky Zener or transistor within the circuit damaged by the lightning; so, the required references for certain circuits used by the Laptop to conserve power, are corrupt. So the Battery is dependent let's say on that circuit to provide warning or to shutdown.

Ultimately, the main difference I see in a Tower vs Laptop. it doesn't depend on a charging circuit for the battery. This might explain why it can't process it or refuses on a Laptop.

 

[undee.sun]

Hi killivolt, thanks for your reply,
I also ever thought that probably the manufacturer reduce the power or increase the efficiency or somehow that make the new VGA card has weaker signal than the old one. And my monitor because of the lighting makes the amplifier circuit has partially damaged that need strong signal to operate it, and the old VGA card has this capability, just my thought. I ever find the VGA booster but could not found the cheap one yet. I am just thinking how to build a simple VGA booster, maybe using some transistors.

The problem is not between the tower / PC desktop and the laptop, but it is between the old PC and the new one either tower or laptop. So it looks like there is a difference between classic VGA card and the new one.