Solved

LapTop Monitor Not working ???

Posted on 2006-06-27
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Last Modified: 2011-08-18
Hello Everyone, This is the same question which i have opened in the hardware TA.
http://www.experts-exchange.com/Hardware/Q_21896519.html

But I couldn't find any solution or even a pointer to my problem that could let me know where I am exactly and if i was able to fix it or not, but the experts were very helpful with their comments. So I decided to close  the question but i still have the problem and I need to know a specific cause in case my monitor was the problem.

The problem is being explained in the link above, Any help is much appreciated.
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Question by:Mohammed Hamada
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Assisted Solution

by:SteveG00000
SteveG00000 earned 100 total points
ID: 16997448
It could be one of two things, firstly you may have dammaged the switch that the lid depresses when it is closed, this switch turns off the backlight on the screen, or the problem could be the backlight inverter, this is a module inside the screen or laptop that controls the backlight.  More than likely it would be the inverter that is causing the problem.

Have tried looking for a service manual but not found one.  Hope this is of help.
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Watzman earned 200 total points
ID: 16997820
I would never have recommended that you disassemble anything.

Some fundamentals:  The LCD display panel is lit from behind by an "optical stack" whose light source is a CCFT (cold cathode fluorescent tube ... a fluorescent light tube, almost like you probably have in your kitchen).  The lamp is inside the LCD panel but is logically separate (and in most cases can, if necessary, be replaced separately).  This lamp requires high voltage (400 to 1,500 volts .... VERY DANGEROUS, by the way) that comes from an "LCD Inverter", a small power supply board located outside the LCD module but still in the lid of the laptop.  Usually it's about 1/2-inch wide by 3 to 4 inches long.  Sometimes it's kind of hidden inside the LCD cabling in a section that is made of shrink tube.

For whatever reason, your backlight is going out.  Could be the lamp, could be the inverter (inverter failure is more common than lamp failure) or it could be that the inverter is being told to shut down by the laptop.  There is a switch that turns off the inverter when the lid is closed, that's the little post .... and yes, those sometimes do cause problems, but that doesn't sound like it was your problem originally (not sure, however, that you didn't damage it).

Inverter failure is the most common single cause of these problems.  Beyond that, without seeing the laptop, it's hard to say what's going on.  BE CAREFUL WORKING AROUND THE INVERTER, THE HIGH VOLTAGE OUTPUT CAN BE VERY DANGEROUS, EVEN LETHAL.
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by:Mohammed Hamada
ID: 16997822
what do you think i can do now ? am i still able to fix this screen or i should go buy a new monitor ?
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by:Watzman
ID: 16998417
When you say "monitor", do you mean the display in the lid of a laptop, or some external monitor?  Your terminology is imprecise and confusing.  I'm not sure that you shouldn't get professional help with the repair, but the next step may be to look for a replacement inverter.
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by:garycase
garycase earned 200 total points
ID: 17006651
I've reviewed your previous question, and there are three possibilities; although the 3rd is almost certainly your issue:

(1)  A bad lid-closed sensor switch (the little switch you referred to) => this is unlikely, as you wouldn't have been able to restore the display by pressing on it, and the problem wouldn't have been transient;

(2)  a bad inverter => this is possible, but not as likely as #3, since the display is still apparently being powered (you can "see" it, but it's just too dim to be useable -- is this still true??);

(3)  a bad backlight =>  this is the most likely problem.

Since you're in the UK, I'd suggest you call these guys and discuss your problem with them.  Backlight replacements shouldn't be too expensive (they aren't cheap, but they're certainly not nearly as expensive as a new laptop, as you indicated in your first question):  
http://www.laptopsupport.co.uk/acer-laptop-repair-uk.html

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Expert Comment

by:Watzman
ID: 17009872
Garycase's comments re: his #2 are not correct.  The Inverter is a more likely cause than the lamp (although either IS possible).  The fact that the display is being powered in no way clears the inverter.  The inverters is a very high-voltage device (400 to 1,600 volts), and it has high voltage swtiching transistors, and these fail, also high voltage pulse transformers, and high voltage capacitors, they all fail.  The issue is not whether the inverter has power, the issue is whether it's working.  You could find out by measuring it's output, but this is DANGEROUS, I don't recommend doing it (and you probably don't have anything capable of measuring over 1,000 volts of high frequency AC anyway).

As to his list, 1 thru 3, the list is ok, but we need to add one more item:

(4) for whatever reason (could be hardware or could be a setting) the motherboard is telling the inverter to turn off

The motherboard has logic control of the inverter ... on-off, and, usually, on most models, brightness.  It's possible (unlikely, I think, but possible) that the motherboard is telling the inverter to turn off (as it does, for example, when you close the lid and the lid closed sensor switch is working normally ... the switch is not an inverter power switch, but is simply a logic sensor used by the motherboard and the software.  It's the software and other hardware that actually do the turning off).
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Expert Comment

by:garycase
ID: 17010071
I did state #2 incorrectly -- the inverter doesn't produce the display;  but what I meant was the fact that you could originally get a display by "hitting" the switch indicates that the inverter is still working (at least intermittently) => and the fact it eventually quit doing that can easily mean a defective backlight.   But I agree it can be EITHER the inverter or the backlight, and it's really difficult to know which without disassembling the laptop to the point you can (carefully) take some voltage measurements.   I'd suggest you contact the folks I provided a link to above.
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by:Mohammed Hamada
ID: 17013113
Thank you Watzman for the brilliant explanation, however I haven't find the inverter at the computer market.
And I can't get it on "ebay" due to country problem, the country i live in is not currently listed on ebay, If i wanted to goto different country to buy this 5 dollars inverter then I guess im a dumba$$.

@ garycase, i'm not in u.k, where did you hear this rumor lol ?

Anywayz you are totally right about your comment, the switch or the pin that switch the laptop to stand by mode is working and i have already tested it, so do you think it's not the inverter relyin on pin is good ?

some questions to make my self clear.

Watzman, changing the backlights of the display is not an easy thing ..!!? do you have any website that would explain doing it?

Garycase, what do you think about buying a new display for the monitor? I'm able now to change it, as i have found the connector between the display and the mobo.

I guess that buying a new one will cost about 300$, I just wanna get rid of this problem..!

Thank you guys alot
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by:garycase
ID: 17013389
"... @ garycase, i'm not in u.k, where did you hear this rumor lol ? ..." ==>  You made this comment in your previous question:  "I will leave the question open for more experts to see and give their opinions about it. In case there was away to fix this i'll take it with me on july as i'm going to Palestine/Isreal and I guess there they can fix it for less price than U.K."

I assumed since you said "I guess there they can fix it for less price than U.K." that you were in the U.K.

I do NOT think you need a new display => either an inverter or a backlight will fix this; and the repair cost in the US (is that where you are now??) should be in the $100 - $150 range.  These guys advertise a range of $120 to $150:  http://www.247laptoprepair.com/laptop-lcd-backlight-repair.htm
... or call these guys for a quote:  http://www.laptop-computer-repairs.com/www.notebook-repair.net/Acer_laptop_repair_LCDrepair.net.html

... or you could just buy a new inverter for $80 and backlight for $10 and replace them both yourself (or just try the backlight first -- and then the inverter, since the cost is so low to confirm whether or not it's the backlight).   You can buy backlights here:  http://www.lcdpart.com/doc/ccfl.html
... and inverters here:  http://www.blisscomputers.net/Acer-laptopinverterrepair.htm

Neither the backlight nor the inverter are "hard" to do -- but they do require that you disassemble the laptop to some degree.   If you're not comfortable doing this, then send it off for repair !!


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Expert Comment

by:Watzman
ID: 17013574
Everything that you have said indicates that you don't need a new display, even if you do need a new backlight lamp (which is located inside the display).  Changing the display to replace the lamp is a very expensive way to do it, although in fact that is probably how it is usually done (either due to mis-diagnosis, or due to service depots that don't change the lamp alone, although they could).

The difficulty of changing the lamp varies enormously.  Some [many] laptops are actually pretty easy to change, no more than 4 screws (sometimes only one) and the lamp is easily removed.  BUT, I won't argue, some are next to impossible, in fact some are literally impossible without total panel disassembly.  And, unfortunately, there are no "general" instructions, because every LCD panel is different.  In fact, if you look in a typical Toshiba laptop service manual, they normally give these instructions, and there are normally 3 to 5 LCD panels used, and 3 to 5 sets of lamp replacement instructions, in the SAME MODEL of laptop.  I will say that for an experexperienced laptop technician, it's usually possible to figure out how to do it by very closely looking at the panel, even with no instructions.  However, for a novice, the first several attempts to do it usually destroy what was a good LCD panel.

I still think that the odds of it being the inverter and not the Lamp are something like between 3:1 and 8:1.

Even if you have to buy an inverter, they are usually under $100.  Lamps are $10 to $25 bought as bare lamps, or $50 to $150 bought as lamp assemblies (with wiring harnesses and end caps).  If you buy a bare lamp (digikey and mouser, among other places, sell them), cut the old wiring harness off the old lamp as close to the glass as possible and reuse it.  The wiring is silver plated and specialized, you can't use "ordinary" copper wire.
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by:Mohammed Hamada
ID: 17026846
Garycase, thanx for this useful links.

however I live in Libya/ North africa, there isn't much computer spare parts here, esp the laptop as they are not very  common and they r expensive, I bought this one from a friend of mine 2 years ago it was new and so cheap about 800$.

Anywayz, the last words you say gives me a hope that I can still fix it, and yes i can disassemble it. but I still have to look for these spare parts, the lamps or the inverter to replace the bad ones.

Watzman...
this is a good information, But do you know if it's easy to remove these lamps on Acer aspire 1400 lcd monitor ?
I guess I can trust your experince. but I wanna know if i'm able before I disassebmle the monitor.

I found an inverter on ebay on my previous thread by one of the experts for 5 or 10 $, I'll try to order it when I'm in Palestine.

Will provide more information when finding the spare parts.

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Expert Comment

by:Watzman
ID: 17027089
No way to know without examining it.  Note that the same laptop (Acer aspire 1400) can be built with different LCD panels, so the laptop model alone is insufficient information.
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Author Comment

by:Mohammed Hamada
ID: 17027116
OHH, Like what LCD panels ? can u list them please ??
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Author Comment

by:Mohammed Hamada
ID: 17079931
Hello Watzman? can anyother one help me with finding a compatible lcd monitor that fits my acer aspire 1400 laptop?
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by:Watzman
ID: 17080521
First of all, please stop calling it an LCD monitor, unless that is what you mean.  An LCD monitor is an external monitor (like you would use with a desktop, although you could also use it with a laptop).  What you are asking about is an LCD panel, not an LCD monitor.

Second, however, I don't think that the panel itself is the problem, I think that the problem is the backlight lamp (inside the LCD panel, but separately replaceable) or the inverter.

Third, the model number of the computer (Acer Aspire 1400) is not sufficient information, because it is very likely that Acer Aspire 1400's were built by Acer using a variety of different LCD panels from different manufacturers.  What we need to know is the manufacturer and model number of the LCD panel, not the computer.  And this can only be determined by opening up the lid and removing the LCD panel.

Even so, finding LCD panels, backlights or inverters (any or all) at reasonable prices is very difficult.  And finding a replacement lamp might require removing the old lamp from the LCD panel, which I can't tell you how to do.  In fact, it's not something for a novice to undertake at all, as it is different for virtually every single panel, and in some cases it is VERY difficult (in other cases it's easy).

The most straightforward way to attack this (although perhaps one of the more expensive ways) is directly through Acer with a service manual (or parts manual).  Unfortunately, these too can be difficult to come by, depending on the mfgr. and model.

My real conclusion here is that you try to find an Acer authorized repair facility to do the repair.  Considering the difficulty of getting both parts and even information, and the potential difficulty of the repair itself, I think that your chances of completing this entirely on your own are not that good.
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LVL 23

Author Comment

by:Mohammed Hamada
ID: 17159735
Thanx everyone for the contribution... I have not done anything yet ... Still wanting to travel to get the spare parts and might take the panel with me..

Thanx watzman for the correction.

Much appreciated.
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