Toshiba Laptop w/dark screen

[octoolguy]

I have an older laptop so I can't spend much to fix it. It has a dark screen but the image is still viewable with a flashlight. I have replaced the inverter, the light bulb, and the harness from the motherboard to the inverter to no avail. I'm at the end of my technical ability so I am asking for help. I bought the inverter and the bulb new from a parts supplier and the harness is used from Ebay. Can anyone give me some idea of what might be the problem? Does the motherboard send a signal to the screen to light up? Could it be the motherboard? As you can see, I'm not an expert but I like to try to fix things myself. HELP!!!!

P.S. It's a Toshiba A55-S306 running XP with 1 gig of ram and a 160 gig h/d.

Ray

 

[Steltek]

If it has a VGA output, try hooking the laptop up to an external monitor to see if the output is normal. If it is normal on the external monitor, the LCD panel may be dead. If the external monitor output doesn't work properly, it is likely to be a more serious hardware problem with the onboard graphics.

Probably a stupid question, but you did get the correct models of inverter and/or backlight for the laptop? Did you try the new inverter with the old backlight instead of replacing both of them? Sometimes, one or the other will go bad, but not usually both. Most often in my experience it is the inverter.

 

[octoolguy]

Hi Steltek and thanks for taking the time to reply. I compared the parts that I bought and they appeared to be identical. I first bought the inverter and gave it a try but no go. So then I ordered the bulb and gave it a try with both inverters. Still no go. So, I found a used harness on ebay and tried it with all combinations. No go. Going back to the beginning here, when it first started happening, I was able to get it to flicker by touching the screen at the bottom. Then I figured out how to remove the bezel and was able to wiggle the wiring on the inverter and get the screen to come on. I actually got it working pretty well. My intentions were to get it all squared away with a fresh copy of XP and give it to a friend. I waltzed into her home and was all prepared to show her how to use it and the screen was again blank. So, back to square one. I am pulling out my hair trying figure out if I got a defective inverter in the first place. I can't spend anymore money on this thing so I am still trying to figure it out. I just put an offer in on ebay for a parts laptop that has a working screen. If I can get it for a decent price I will have one good laptop and a box of extra parts. I'll try what you suggested with hooking it to a monitor. I'll get back to you as soon as I have an answer. Thanks again,

Ray

 

[mfenn]

Try measuring input voltage to the inverter to see if it's getting any juice from the motherboard.

 

[octoolguy]

Try measuring input voltage to the inverter to see if it's getting any juice from the motherboard.

I'm not too sure how to go about doing that. Can you give me any details on what to touch and what it should be etc.???

Thanks for your help,

Ray

 

[mfenn]

Do you have a multimeter?

 

[octoolguy]

Yes, I have a multimeter. I am just not too sure as to which terminals to touch or what the readout should be. Am I just looking for output or a specific amount?

Ray

 

[mfenn]

Trace the wires leading to the inverter from the board and then probe each pair. Some should be ground and thus have no voltage difference, but there should be some with a voltage. I'm not sure exactly what it should be on your model, but I'm betting somewhere north of 12V.

 

[octoolguy]

Thanks Mfenn, I'll check it out. Probably won't get to it until tomorrow though. I'll let you know what I find.

R

 

[octoolguy]

Did some probing but with my limited knowledge all I found out was that I got some readings on the input side of the inverter but couldn't get anything out of the output side. Very hard to probe the tiny little pins so I'm really not sure of what I found. But the meter did react to the input side. I just don't know what wires were which. I booted the computer and I still have an image on screen but no light. I'm about ready to send for another inverter. I might have gotten a defective one or maybe in the process of installing it I damaged it. Who knows but at this point, I either have to take it somewhere and pay an exorbitant price to have it fixed or try to muddle my way through it. I'm not sure what to do.

Ray

 

[octoolguy]

Hi again, I tried connecting my laptop to a monitor and I got a desktop like the one on the laptop but without any icons. I'm not sure what or how to set the monitor as the default. If someone can tell me that it would be a great help. I tried going into control panel and changing some things under the display but still not icons, mouse pointer or taskbar.

Ray

 

[Steltek]

Hi again, I tried connecting my laptop to a monitor and I got a desktop like the one on the laptop but without any icons. I'm not sure what or how to set the monitor as the default. If someone can tell me that it would be a great help. I tried going into control panel and changing some things under the display but still not icons, mouse pointer or taskbar.

Ray

Windows thinks the laptop LCD is the the primary monitor and is probably using the external as a secondary extended desktop.

Locate the fn key on the keyboard. Then, look across the function keys (F1, F2, etc). One of them probably has a picture of a monitor or TV on it. Hold down the fn key, and press that monitor key to see if this switches the primary display to the external monitor. You may have to cycle through it more than once if it has more than one option.

 

[mfenn]

Windows thinks the laptop LCD is the the primary monitor and is probably using the external as a secondary extended desktop.

Locate the fn key on the keyboard. Then, look across the function keys (F1, F2, etc). One of them probably has a picture of a monitor or TV on it. Hold down the fn key, and press that monitor key to see if this switches the primary display to the external monitor. You may have to cycle through it more than once if it has more than one option.

This or go to the Display Properties page and make the external screen the primary display.

Did some probing but with my limited knowledge all I found out was that I got some readings on the input side of the inverter but couldn't get anything out of the output side. Very hard to probe the tiny little pins so I'm really not sure of what I found. But the meter did react to the input side. I just don't know what wires were which. I booted the computer and I still have an image on screen but no light. I'm about ready to send for another inverter. I might have gotten a defective one or maybe in the process of installing it I damaged it. Who knows but at this point, I either have to take it somewhere and pay an exorbitant price to have it fixed or try to muddle my way through it. I'm not sure what to do.

Ray

The main goal was to see that you had input voltage but no output voltage. That tells me that there is probably something wrong with the inverter.

 

[octoolguy]

Hello to all who have tried to help. I have an update. I did the testing that was suggested but with my multimeter it was a lesson in frustration. So, here is where I am at this point. I did a search on ebay for a parts laptop but I found a working unit exactly like the one I have and it was CHEAP. So I bought it. It works just fine. So, now I have something that I can do some parts swapping with. I had previously purchased an inverter and also a new flourescent bulb. Neither of them did me any good. So, I was at a loss where to go next. I did connect a monitor to the laptop and it worked. So, I was able to see the screen with a flashlight. There is an image and also I could see everything on the monitor. I have a signal to the laptop screen and also on the monitor. So, I did some swapping. I first tried the bulb on the new laptop and it worked. So, I swapped the inverter that I had purchased and it worked. But when I tried swapping the parts from the new laptop to the old laptop, still nothing. So I am at this point. I am not getting a signal from the motherboard/bios to tell the lamp to light. Does that mean that the motherboard is toast or is there something in the bios that has gotten screwed up? I hope this isn't too confusing. If anybody has any ideas besides just junking the old machine and working with the new one. I'm trying to end up with two working laptops so I can give them to a couple of people that need them. Thanks again for all the help so far.

Ray

 

[Steltek]

Usually what you describe is a problem with the inverter. However, that obviously isn't the case here.

The only other thing you could try to do is install the LCD panel from the working laptop into the first one to see if it is a dead panel. You also probably need to trace all the cabling from the panel to the motherboard and make sure no traces are broken or split and that everything is plugged in tightly.

 

[mfenn]

You could always try completely removing all power from the mobo to clear the CMOS (if you haven't already in the course of your troubleshooting).

Failing that, I don't see how you're going to end up with two working computers since you have one critical part that is bad.

 

[octoolguy]

You could always try completely removing all power from the mobo to clear the CMOS (if you haven't already in the course of your troubleshooting).

Failing that, I don't see how you're going to end up with two working computers since you have one critical part that is bad.

My intent is to figure out what is wrong with the first laptop by swapping parts with the second one. If it is cost efficient to buy the defective part and get it working again, I will have two working laptops. But if not, I will at least know what the problem was and still have one good one. I am hoping that it's nothing too expensive to fix. There are a lot of parts machines available on ebay. If it comes down to the screen/display then I will try to find a good one there. Thanks for your help here. I really appreciate it. The whole idea here is to try to keep my 70 year old brain working. A person has to keep learning.

Ray

 

[octoolguy]

Usually what you describe is a problem with the inverter. However, that obviously isn't the case here.

The only other thing you could try to do is install the LCD panel from the working laptop into the first one to see if it is a dead panel. You also probably need to trace all the cabling from the panel to the motherboard and make sure no traces are broken or split and that everything is plugged in tightly.

Thanks Steltek, that is my next task. I was hoping not to have to do that. It's a lot of work and leaves open the possiblility of me screwing up the one good display. I will be very careful and take my time. Thanks again,

Ray

 

[paul878]

Only one thing left, the System board.

 

[octoolguy]

Only one thing left, the System board.

That's what I've been trying to find out. Where does the signal come from that tells the lamp to light? The image is going to the screen but the light just isn't lighting.

R

 

[mfenn]

My intent is to figure out what is wrong with the first laptop by swapping parts with the second one. If it is cost efficient to buy the defective part and get it working again, I will have two working laptops. But if not, I will at least know what the problem was and still have one good one. I am hoping that it's nothing too expensive to fix. There are a lot of parts machines available on ebay. If it comes down to the screen/display then I will try to find a good one there. Thanks for your help here. I really appreciate it. The whole idea here is to try to keep my 70 year old brain working. A person has to keep learning.

Ray

Oh ok, I thought from your previous post that you were done buying new parts.

The signal to the inverter to power on is one of the pins connecting the system board to the inverter input. Since you have two identical machines now, you can probe the contact points and make note of the differences.

That will give you some clue as to where voltage needs to be applied to turn on the inverter. Then you could probably hack something up that keeps the light on by applying voltage to the correct pin on the inverter.

 

[octoolguy]

Sorry Mfenn to have misled you. I don't want to spend a bunch of money on parts unless I know what is the problem. With the second laptop, I now have a way of testing things to see where the problem lies. I am going to try swapping the displays to see if that makes a difference. I have already tried a different cable from the motherboard to the inverter/screen but that didn't help. So, I will get back to you when I have had a chance to tear into both laptops.

Ray

 

[octoolguy]

Ok so here is the update. I placed both laptops side by side and disassembled them. I exchanged all the involved parts including the screens. Everything works on one laptop but the one with the dark screen doesn't work no matter what. There is an image on the screen that can be seen with a flashlight and it works fine with a monitor attached. So, am a dead in the water?

Ray

 

[paul878]

Ok so here is the update. I placed both laptops side by side and disassembled them. I exchanged all the involved parts including the screens. Everything works on one laptop but the one with the dark screen doesn't work no matter what. There is an image on the screen that can be seen with a flashlight and it works fine with a monitor attached. So, am a dead in the water?

Ray

Bad Motherboard?

 

[C1]

What is suspicious is that as stated in the beginning of this post, a lit screen was being attained, but that it was intermittent.

There's an outside chance that there is simply a broken or bad solder joint on the MB. As such, a recommendation is to turn on/energize the defective computer (with LCD screen components connected) and with an insulated tool (such as a wooden dowel) flex the MB, particularly in the area of the display lamp circuit connection to the MB.

You are inspecting/checking for the possibility of bad solder joint that might just make temporary contact to reveal itself when the MB is suitably flexed.

Also by eye, inspect very carefully (under powerful lighting) the MB solder connections looking for anything suspicious - even solder points bridged by a piece of fine trash wire strand.