Screen problem Inspiron 1545

[cherubrock74]

I have a Dell Inspiron 1545 and screen is not working. I can see the icons if I point a flash light to the screen. But without it scren looks almost black.

So far I changed the inverter and the backlight but had no luck!

I have connected an external monitor to it and it works perfectly. I guess my video card is good.

The only thing I haven't changed besides the whole lcd is the cable connector for the lcd. Battery is completely dead, so I am testing it by plugging in the charger. Dont know if this makes any difference. If the lcd was dead I should not be able to see the icons with the flashlight...correct?

Should I change the lcd cable connector too? Or should I just go ahead and order the whole lcd? At this point I just want it to work!...without spending the equivalent of a new computer!

Can you suggest me how to proceed with the troubleshooting?

Anyone? Please help

 

[cherubrock74]

Anderson thank you for your reply
Yes I can see the whole screen using a flashlight
what kind of internal problem you are referring to?
when I connect the laptop to an external monitor I can perfectly see my screen
weird...after I changed the inverter and the backlight I dont want to spend more money into it unless I found the cause...

 

[mavroxur]

More than likely, if you're sure the backlight and inverter are both good and connected properly, the inverter either isn't getting the proper supply voltage from the motherboard, or it isn't getting the turn-on signal from the motherboard. If you're handy with a multimeter (and have one) you can check for a supply voltage. The easiest way (be careful to NEVER touch the intverter output, in case it comes on unexpectedly) to check the supply voltage is to measure from the fuse on the inverter (usually a poly fuse or a picofuse) on the supply side (the side that has traces that connect to the IDC / ribbon cable) to a known ground point. (which is usually a ground plane point around a screw hole on the inverter, or a grounded shielding point around the cable connection. With the laptop on, you should measure a supply voltage (usually 5v or more, but varies depending on the laptop). You might have to do some google-fu to get the voltage for your model, but from experience, you'll either measure nothing, or the correct voltage. It's usually tapped from a regulated circuit that supplies several things in the laptop. If that voltage is present, you're most likely not receiving the power-on signal at the inverter that instructs it to power the backlight. The exact pin that does this varies from model to model, and you'll need to do your homework to check that. But if that *is* the problem, it's either a cable issue, or a motherboard issue. Check that supply voltage and get back to me.

 

[cherubrock74]

More than likely, if you're sure the backlight and inverter are both good and connected properly, the inverter either isn't getting the proper supply voltage from the motherboard, or it isn't getting the turn-on signal from the motherboard. If you're handy with a multimeter (and have one) you can check for a supply voltage. The easiest way (be careful to NEVER touch the intverter output, in case it comes on unexpectedly) to check the supply voltage is to measure from the fuse on the inverter (usually a poly fuse or a picofuse) on the supply side (the side that has traces that connect to the IDC / ribbon cable) to a known ground point. (which is usually a ground plane point around a screw hole on the inverter, or a grounded shielding point around the cable connection. With the laptop on, you should measure a supply voltage (usually 5v or more, but varies depending on the laptop). You might have to do some google-fu to get the voltage for your model, but from experience, you'll either measure nothing, or the correct voltage. It's usually tapped from a regulated circuit that supplies several things in the laptop. If that voltage is present, you're most likely not receiving the power-on signal at the inverter that instructs it to power the backlight. The exact pin that does this varies from model to model, and you'll need to do your homework to check that. But if that *is* the problem, it's either a cable issue, or a motherboard issue. Check that supply voltage and get back to me.

Hi Mavroux

I am not familiar with how the inverters are built and where the fuses are...but I do have a multimeter and I have attached an image of my inveter...is there any way you can point me to where I should check the voltage?

 

[jdenova007]

You changed the backlights? I doubt it, those are integrated into the LCD Screen. You need to literally take the LCD Screen apart in order to replace those... they are very thin, long bulbs..

Your issue is one of two things.... Bad motherboard(not giving the proper signal to the LCD) or Bad LCD Screen. LCD screen is usually the culprit(around 80% of the time). If your External monitor works fine, then it makes your motherboard even less likely of two... but it can still be the problem. You may have to take a shot in the dark....

 

[cherubrock74]

You changed the backlights? I doubt it, those are integrated into the LCD Screen. You need to literally take the LCD Screen apart in order to replace those... they are very thin, long bulbs..

Your issue is one of two things.... Bad motherboard(not giving the proper signal to the LCD) or Bad LCD Screen. LCD screen is usually the culprit(around 80% of the time). If your External monitor works fine, then it makes your motherboard even less likely of two... but it can still be the problem. You may have to take a shot in the dark....

Thank you for replying jdenova007
Yes I did change the backlight...why would you have a doubt about it? LOL
I took the whole lcd apart and replaced the backlight bulb...I know what it looks like because I had to order a new one and replace the existing one
unfortunately I had no luck...so far inverter and backlight were replaced...thats why I decided to post here and see if someone would help me troubleshooting it
it seems not easy to do but I think testing the voltage is a good idea...the only thing is I dont understand how to test it even if Mavroux provided a good description

 

[jdenova007]

My bad, figured you wouldn't take the LCD apart. My apologies for considering you a noob... lol...

I can't help with voltage checks. Sorry. (When I see circuit boards with Fuses... they are usually labeled with a 'F'... like F7 - means 'Fuse 7'. Your inverter may or may not label these little Fuses... they can be REALLY small...

But if you replaced the backlight and inverter... and the LCD does in fact work because you can see the items using a flashlight.... then the likely culprit is the motherboard not giving the proper signal to LCD Screen to "turn on". I'd got with motherboard now. (or you could try a cable because it would be much cheaper, they usually don't go bad though) (you could test the cable with the multi-meter just to make sure you have continuity from one end of the cable to the other, that would pretty much rule out a bad cable)

 

[cherubrock74]

My bad, figured you wouldn't take the LCD apart. My apologies for considering you a noob... lol...

I can't help with voltage checks. Sorry. (When I see circuit boards with Fuses... they are usually labeled with a 'F'... like F7 - means 'Fuse 7'. Your inverter may or may not label these little Fuses... they can be REALLY small...

But if you replaced the backlight and inverter... and the LCD does in fact work because you can see the items using a flashlight.... then the likely culprit is the motherboard not giving the proper signal to LCD Screen to "turn on". I'd got with motherboard now. (or you could try a cable because it would be much cheaper, they usually don't go bad though) (you could test the cable with the multi-meter just to make sure you have continuity from one end of the cable to the other, that would pretty much rule out a bad cable)

Good idea of testing the cable with the multimeter...I will do it this afternoon and post back here the result
I am not familiar with how the interters are built and how to test the fuses...but I am starting to consider the mobo as the source of the problem...if so I will sell the parts and use the money towards a new laptop

 

[mavroxur]

Hi Mavroux

I am not familiar with how the inverters are built and where the fuses are...but I do have a multimeter and I have attached an image of my inveter...is there any way you can point me to where I should check the voltage?

http://www.napcon-communications.com/images/IMAG0065.jpg

There's no way for me to point you exactly to it from that picture, but normally the fuse is located near the ribbon cable / IDC that goes to the motherboard, and it's usually labeled "F", "FUSE" or "F" with a number of some sort (F2, F3.5, F3A, etc). If you took a close up picture of it with the sleeve removed, I could point you to it, but it's not hard to find.