Laptop monitor is black

LUFINI · 11-28-2009, 01:20 PM

I had posted this on someone else's thread, so wanted to start my own thread. I have a Toshiba Satellite A35 laptop which has worked beautifully for a number of years. Then one day the monitor just went black. It flashes on briefly when I start it up, and I can hook the laptop up to another monitor and then have no problem working with the laptop. If I toggle back and forth between the laptop and the external monitor, I get a brief flash of the screen on my laptop before it goes black again. I have taken the battery out and held the power switch down (didn't work). I have replaced the inverter (didn't work) and the last suggestion was to replace the backlight, which I've now ordered. However, is it possible there are some drivers missing or that were deleted with OS updates (XP)? And if that's a possibility, how would I check?

**TriggerFinger** · 11-28-2009, 03:19 PM

If you get a screen on an external monitor then it may not be the video drivers causing this. This might be caused by the LCD itself (possibly backlight or inverter or the cable or the LCD). When using the LCD, can you see however faint the Desktop?

LUFINI · 11-29-2009, 04:36 AM

I can see that something is there but it is so faint I can't make anything out.

**TriggerFinger** · 11-29-2009, 07:50 AM

Try putting a flashlight near the screen. If you see your Desktop then it could be a backlight or inverter problem.

LUFINI · 11-30-2009, 06:52 AM

With a flashlight I can definitely see the desktop. I've ordered a backlight and will let you know if that solves the problem. Thanks, all, for your help.

LUFINI · 01-08-2010, 11:43 AM

I have not had much success. I bought a new backlight and hired a computer repair person to replace it, but the light needed to be soldered on and in the process, the little light tube broke. So, I bought a refurbished Satellite A35 screen which was supposedly in good working condition. I hooked that up, but no success. The screen is still black. I can use an external monitor with no problem. If I toggle back and forth between the two screens, my laptop screen flashes in color real quickly and I can see that the screen is the same as the external monitor screen, but then it goes black again. If I shine a flashlight on my black screen, I can see the very faint print on the screen. I've replaced the inverter with a new inverter but that doesn't work either. Any suggestions? I'd like to be able to use my laptop screen.

**TriggerFinger** · 01-08-2010, 04:41 PM

Very strange. Does it do that even when you just boot into BIOS? When you press the power ON button (while laptop is still OFF), do you see anything on the laptop screen like the logo splash or POST?

LUFINI · 01-09-2010, 12:28 PM

When I first press the on button, I get a really quick Toshiba flash across the screen in color. It lasts less than a second and then the screen goes black. If I try and get into the BIOS at startup, once the Toshiba flash disappears, I can't seen anything else without using an external monitor. The screen seems to be working, but it just won't stay lit.

night_shift · 01-09-2010, 04:57 PM

Hello LUFINI

As TriggerFinger has said "Very strange" there are only a couple of faults that can cause this. So we will eliminate the LCD screen as you can faintly see your desktop on it. So....

1. You need to check the voltage to the inverter (you need a multimeter with AC and DC voltage ranges up to 1000 Volts), should be about your laptop dc supply around 12 to 20 volts if you aint getting this, the supply cable could be open circuit from mobo to inverter. The other side (output to backlight) is high voltage AC from 500 to 900 volts "BIG CAUTION"!!! DO NOT TOUCH WITH FINGERS!!!!
2. If you have the dc voltage and you know the inverter is giving an output (aprox 500 to 1000V) and lcd backlight is good then could be a bad cable from inverter to lcd backlight tube.

We will assume inverter and backlight are ok and voltages for inverter input and output are ok. Using a multimeter on ohms check the continuity of the wires from inverter to backlight.

If you are not confident to do the above, take it to your "computer repair person" and get them to check the voltages and cable continuity.

LUFINI · 01-10-2010, 09:28 AM

Thanks. I'll need to get someone to help me on this. I'm not getting much in the way of readings off my multimeter and getting to the backlight is problematic because it means taking the screen entirely apart. I'll let you know what happens.

night_shift · 01-10-2010, 11:15 AM

Cool. Good luck.

LUFINI · 01-11-2010, 06:07 AM

I had someone else help me on this. We tested the voltage from the end of the inverter that goes to the light and were not able to get any reading, although it is difficult getting contact from the tiny openings we were dealing with here. We tried this on both the original inverter and the brand new inverter and had the same result. We then tested the voltage going into the inverter and saw a reading of 8 DC before it generated a spark that turned off the machine. I have to assume that meant there was power going into the inverter but the inverter might be bad - which is strange since this inverter was bought brand new (supposedly). We also tested the continuity of all the wires and had readings for everything, including at the end of the inverter going to the light. Because the light is buried in the screen, we didn't test the light. So, I've concluded that this may be an inverter problem (although I'm not convinced) and I'm resigning myself to no longer having a portable but staying hooked into an external monitor. I'm not a smiley face person, but I couldn't resist this one.

11-28-2009, 01:20 PM	#1 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Laptop monitor is black I had posted this on someone else's thread, so wanted to start my own thread. I have a Toshiba Satellite A35 laptop which has worked beautifully for a number of years. Then one day the monitor just went black. It flashes on briefly when I start it up, and I can hook the laptop up to another monitor and then have no problem working with the laptop. If I toggle back and forth between the laptop and the external monitor, I get a brief flash of the screen on my laptop before it goes black again. I have taken the battery out and held the power switch down (didn't work). I have replaced the inverter (didn't work) and the last suggestion was to replace the backlight, which I've now ordered. However, is it possible there are some drivers missing or that were deleted with OS updates (XP)? And if that's a possibility, how would I check?

11-28-2009, 03:19 PM	#2 (permalink)
TriggerFinger Moderator Hardware Team Join Date: Jan 2008 Location: USA Posts: 11,945 OS: Vista SP1, XP SP3, PCLinuxOS2007	Re: Laptop monitor is black If you get a screen on an external monitor then it may not be the video drivers causing this. This might be caused by the LCD itself (possibly backlight or inverter or the cable or the LCD). When using the LCD, can you see however faint the Desktop? __________________ DBAN - Memtest86+ - BartPE - Linux LiveCD - ImgBurn - HDD Diags - Disk Copy HOW TO BURN AN ISO FILE

11-29-2009, 04:36 AM	#3 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Re: Laptop monitor is black I can see that something is there but it is so faint I can't make anything out.

11-29-2009, 07:50 AM	#4 (permalink)
TriggerFinger Moderator Hardware Team Join Date: Jan 2008 Location: USA Posts: 11,945 OS: Vista SP1, XP SP3, PCLinuxOS2007	Re: Laptop monitor is black Try putting a flashlight near the screen. If you see your Desktop then it could be a backlight or inverter problem. __________________ DBAN - Memtest86+ - BartPE - Linux LiveCD - ImgBurn - HDD Diags - Disk Copy HOW TO BURN AN ISO FILE

11-30-2009, 06:52 AM	#5 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Re: Laptop monitor is black With a flashlight I can definitely see the desktop. I've ordered a backlight and will let you know if that solves the problem. Thanks, all, for your help.

01-08-2010, 11:43 AM	#6 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Re: Laptop monitor is black I have not had much success. I bought a new backlight and hired a computer repair person to replace it, but the light needed to be soldered on and in the process, the little light tube broke. So, I bought a refurbished Satellite A35 screen which was supposedly in good working condition. I hooked that up, but no success. The screen is still black. I can use an external monitor with no problem. If I toggle back and forth between the two screens, my laptop screen flashes in color real quickly and I can see that the screen is the same as the external monitor screen, but then it goes black again. If I shine a flashlight on my black screen, I can see the very faint print on the screen. I've replaced the inverter with a new inverter but that doesn't work either. Any suggestions? I'd like to be able to use my laptop screen.

01-08-2010, 04:41 PM	#7 (permalink)
TriggerFinger Moderator Hardware Team Join Date: Jan 2008 Location: USA Posts: 11,945 OS: Vista SP1, XP SP3, PCLinuxOS2007	Re: Laptop monitor is black Very strange. Does it do that even when you just boot into BIOS? When you press the power ON button (while laptop is still OFF), do you see anything on the laptop screen like the logo splash or POST? __________________ DBAN - Memtest86+ - BartPE - Linux LiveCD - ImgBurn - HDD Diags - Disk Copy HOW TO BURN AN ISO FILE

01-09-2010, 12:28 PM	#8 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Re: Laptop monitor is black When I first press the on button, I get a really quick Toshiba flash across the screen in color. It lasts less than a second and then the screen goes black. If I try and get into the BIOS at startup, once the Toshiba flash disappears, I can't seen anything else without using an external monitor. The screen seems to be working, but it just won't stay lit.

01-09-2010, 04:57 PM	#9 (permalink)
night_shift Hardware Tech Team Join Date: Sep 2009 Location: UK Posts: 503 OS: Vista, XP Pro, Ubuntu	Re: Laptop monitor is black Hello LUFINI As TriggerFinger has said "Very strange" there are only a couple of faults that can cause this. So we will eliminate the LCD screen as you can faintly see your desktop on it. So.... 1. You need to check the voltage to the inverter (you need a multimeter with AC and DC voltage ranges up to 1000 Volts), should be about your laptop dc supply around 12 to 20 volts if you aint getting this, the supply cable could be open circuit from mobo to inverter. The other side (output to backlight) is high voltage AC from 500 to 900 volts "BIG CAUTION"!!! DO NOT TOUCH WITH FINGERS!!!! 2. If you have the dc voltage and you know the inverter is giving an output (aprox 500 to 1000V) and lcd backlight is good then could be a bad cable from inverter to lcd backlight tube. We will assume inverter and backlight are ok and voltages for inverter input and output are ok. Using a multimeter on ohms check the continuity of the wires from inverter to backlight. If you are not confident to do the above, take it to your "computer repair person" and get them to check the voltages and cable continuity. __________________ Please Post Back It’s nice to know if the Forum has helped or not Last edited by night_shift; 01-09-2010 at 04:59 PM.

01-10-2010, 09:28 AM	#10 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Re: Laptop monitor is black Thanks. I'll need to get someone to help me on this. I'm not getting much in the way of readings off my multimeter and getting to the backlight is problematic because it means taking the screen entirely apart. I'll let you know what happens.

01-10-2010, 11:15 AM	#11 (permalink)
night_shift Hardware Tech Team Join Date: Sep 2009 Location: UK Posts: 503 OS: Vista, XP Pro, Ubuntu	Re: Laptop monitor is black Cool. Good luck. __________________ Please Post Back It’s nice to know if the Forum has helped or not

01-11-2010, 06:07 AM	#12 (permalink)
LUFINI Registered User Join Date: Apr 2009 Posts: 20 OS: win xp	Re: Laptop monitor is black I had someone else help me on this. We tested the voltage from the end of the inverter that goes to the light and were not able to get any reading, although it is difficult getting contact from the tiny openings we were dealing with here. We tried this on both the original inverter and the brand new inverter and had the same result. We then tested the voltage going into the inverter and saw a reading of 8 DC before it generated a spark that turned off the machine. I have to assume that meant there was power going into the inverter but the inverter might be bad - which is strange since this inverter was bought brand new (supposedly). We also tested the continuity of all the wires and had readings for everything, including at the end of the inverter going to the light. Because the light is buried in the screen, we didn't test the light. So, I've concluded that this may be an inverter problem (although I'm not convinced) and I'm resigning myself to no longer having a portable but staying hooked into an external monitor. I'm not a smiley face person, but I couldn't resist this one.