Simple Laptop Screen Replacement, Not So Simple?

[nXtGenPC]

Ok so I got this laptop that needed a screen replacement ok so no problem we replace 20-30 screens a month.

I plugged the laptop into an external monitor to make sure all was well and it was

Went ahead and ordered a new screen installed it and no luck

Ok so it's the inverter, so I went and ordered one of those

Inverter still didn't do the trick

So what's up? I laid out the money for the screen and the inverter, any advise

It's a Dell 1420

 

[iptech]

A new mainboard. The Dell 1420 suffers from the same Nvidia chipset issues as many HP/Compaq machines.

 

[schwags]

I agree - Most likely a new mainboard. I have run into this a few times. the mainboard does not put out a signal to the inverter to light up the screen.

The only other thing I have found to cause this is a bad lid switch. if your computer has one of those, try unplugging it and seeing if that helps.

 

[Martyn]

I had a laptop recently(not this model) where it was the cable that runs from the main board to the inverter/screen. It looked fine and was tiny so couldn't meter it(didn't have the pinouts anyway. I ordered it as a last resort before going for the mb, it only cost a few £s on Ebay

 

[14049752]

Ok so I got this laptop that needed a screen replacement ok so no problem we replace 20-30 screens a month.

I plugged the laptop into an external monitor to make sure all was well and it was

Went ahead and ordered a new screen installed it and no luck

Ok so it's the inverter, so I went and ordered one of those

Inverter still didn't do the trick

So what's up? I laid out the money for the screen and the inverter, any advise

It's a Dell 1420

Advice: Figure out a better way to diagnose things than just ordering parts.

What were the original symptoms? No video? Cracked screen? No backlight? Other than a cracked screen (which is obvious), there are ways you can test to be more sure about the parts your ordering.

 

[nXtGenPC]

Advice: Figure out a better way to diagnose things than just ordering parts.

What were the original symptoms? No video? Cracked screen? No backlight? Other than a cracked screen (which is obvious), there are ways you can test to be more sure about the parts your ordering.

I did say that I hooked the laptop up to an external monitor and all was fine and dandy. The laptop seems to be running fine when connected to an external monitor, just when I use the monitor the display doesn't come up

 

[14049752]

I did say that I hooked the laptop up to an external monitor and all was fine and dandy. The laptop seems to be running fine when connected to an external monitor, just when I use the monitor the display doesn't come up

Yes, but that's not enough.
Before ordering parts, I would have checked to see if there was an image on the screen or if it was a bad backlight. No image = bad cable or bad video circuitry most of the time. For that, an inverter wouldn't even come into play. If there's an image, but it's completely dark, you can shine a flashlight behind the lcd to see the image...then the inverter is an option.

As for the LCD, usually you'll have some kind of picture even if the display is bad. Again, maybe the backlight is broken and you can use the flashlight...or it might have lines in the display or cuts out at certain angles, whatever. You can sometimes determine if it's the LCD or the cable by applying slight pressure to the LCD panel and the picture will get better or worse for a split second.

The LCD cable can be checked over for signs of damage, or again, you can sometimes move the screen at the right angle and it will come on.

But, then...knowing that it's a 1420, it's probably the gpu issue.


My only point was that clearly now you're sitting on two parts that cost money, and to me it sounds like a little logical diagnostic testing would have pointed you somewhere eles. (Also, I'm not trying to insult, I'm genuinely trying to give advice for next time so that you don't have to buy parts to find out that you don't need them.)

 

[xxsilk109xx]

I would say its the lcd cable as well. I had a similar issue, there was no visible damage to the cable that I could tell, but I ordered one and it worked.

 

[shamrin]

Yes, but that's not enough.
Before ordering parts, I would have checked to see if there was an image on the screen or if it was a bad backlight. No image = bad cable or bad video circuitry most of the time. For that, an inverter wouldn't even come into play. If there's an image, but it's completely dark, you can shine a flashlight behind the lcd to see the image...then the inverter is an option.

As for the LCD, usually you'll have some kind of picture even if the display is bad. Again, maybe the backlight is broken and you can use the flashlight...or it might have lines in the display or cuts out at certain angles, whatever. You can sometimes determine if it's the LCD or the cable by applying slight pressure to the LCD panel and the picture will get better or worse for a split second.

The LCD cable can be checked over for signs of damage, or again, you can sometimes move the screen at the right angle and it will come on.

But, then...knowing that it's a 1420, it's probably the gpu issue.


My only point was that clearly now you're sitting on two parts that cost money, and to me it sounds like a little logical diagnostic testing would have pointed you somewhere eles. (Also, I'm not trying to insult, I'm genuinely trying to give advice for next time so that you don't have to buy parts to find out that you don't need them.)

Practically speaking, it's hard to see how the OP would have ended up in a different position had he followed your methodology here (this is not to say it's bad advice). He actually eliminated the GPU issue by testing with an external monitor.

If the screen was blank or dark it would have been quite reasonable to diagnose the display or the inverter respectively and then switched to the other when that didn't work. Testing the inverter with a known good screen might have saved him ordering the inverter though.

If the problem does turn out to be the cable, that one comes back to bite everyone in the a** now and then because it's so hard to identify and so seldom the problem.

 

[14049752]

He actually eliminated the GPU issue by testing with an external monitor.

No he didn't. The GPU issue can still be the factor when you get external display but nothing on the LCD.

If the screen was blank or dark it would have been quite reasonable to diagnose the display or the inverter respectively and then switched to the other when that didn't work. Testing the inverter with a known good screen might have saved him ordering the inverter though.

Again, no. If the screen is blank, entirely, the inverter has NOTHING to do with it. The inverter lights the screen, it has nothing to do with what's displayed. That's why I said use a flashlight to see if it's displaying anything but it's dark.
Additionally, searching my memory, I can't remember a single instance where there was no image at all and the LCD was at fault (which isn't to say it's not possible, I just don't think it's likely from my experience). There's a huge distinction between no image and no backlight.

 

[gazza]

No he didn't. The GPU issue can still be the factor when you get external display but nothing on the LCD.


The inverter lights the screen, it has nothing to do with what's displayed. That's why I said use a flashlight to see if it's displaying anything but it's dark.
Additionally, searching my memory, I can't remember a single instance where there was no image at all and the LCD was at fault (which isn't to say it's not possible, I just don't think it's likely from my experience). There's a huge distinction between no image and no backlight.

The inverter provides power to the CCFL bulb it's the bulb that lights the screen. Maybe the bulb is gone? These bulbs are pasta like thin and are generally not replaced but they can break internally from laptops taking knocks. I agree shine a torch light to see if there is images on the screen. If the bulb is gone then replace the entire screen.

Can you explain how the GPU can still be a factor if it works with a external monitor? Thanks.

 

[14049752]

Can you explain how the GPU can still be a factor if it works with a external monitor? Thanks.

Not exactly, to be honest. I assume what happens is that in those cases, the solder breaks connection just enough so that traces leading to the LCD output are damaged when the ones leading to the external video are not. That's only an educated guess.
But, basically, that is one of the possible symptoms given by HP, Apple, Dell, etc. I've run across it numerous times, although typically the external display will have distortion or artifacts in the video.

 

[nXtGenPC]

Used my game console repair skills to reflow the Nvidia chip, works fine with new screen/inverter combo won't work with old screen/ inverter

Killed to birds with one stone

 

[AdamsAPlus]

I can't say for the Dell 1420, but for the HP when the GPU was bad it wouldn't work on the external monitor. The GPU powers the internal and external Monitor. So anytime I have a problem and the external monitor work then I always rule out the GPU. If both do not work then I point to the GPU.

 

[14049752]

So anytime I have a problem and the external monitor work then I always rule out the GPU.

As I mentioned above, you can't really do that. I wish that I could find a source other than me that's saying that, but I've had several HPs that did this exact thing; the external would work but the internal LCD did not.

It almost sounds as if the OP can back me up.

 

[ATTech]

As I mentioned above, you can't really do that. I wish that I could find a source other than me that's saying that, but I've had several HPs that did this exact thing; the external would work but the internal LCD did.

It almost sounds as if the OP can back me up.

That's good to know, perhaps some machines have seperate GPUs.

On an off note, whenever I see the OP's name, I'm always reminded of this guy and how hilarious his videos are.

NextGenHacker

 

[Martyn]

As I mentioned above, you can't really do that. I wish that I could find a source other than me that's saying that, but I've had several HPs that did this exact thing; the external would work but the internal LCD did.

It almost sounds as if the OP can back me up.

I'd be interested to know if this is the case from other techs on here. I haven't done that many screen/inverter repairs and I certainly have not seen the problem whereby the external screen works and the gpu is faulty.

Anyone else have any input here?

 

[14049752]

I'd be interested to know if this is the case from other techs on here. I haven't done that many screen/inverter repairs and I certainly have not seen the problem whereby the external screen works and the gpu is faulty.

Anyone else have any input here?

I just did another one of these today....no video to LCD, external works fine. When I was done, I was REALLY wishing I had started a video of the system. It was a Dell M1530.

I had another one of my tech buddies in the shop while I was troubleshooting it. I checked all of the typical things like the cable, the LCD panel, etc. When I pulled out the reflow equipment, he gave me a look... and I just said "I'll explain...." and then showed him how I do the reflows. When I was done, I popped the board back in and as he put it "I fixed it by cooking it." The LCD panel had video again.

Of course, I explained how it's not necessarily a reliable repair or anything, but still... Like I said, I really wish I had thought to record the process but I was busy and was more concerned with getting work done.

 

[hyfidel]

Sometimes I get nothing on LCD and nothing on external (especially older laptops), just depends on the model. I have this printed out by check-in for easy reference: http://www.nvidiasettlement.com/affectedmodels.html

 

[andcorptech]

I'd be interested to know if this is the case from other techs on here. I haven't done that many screen/inverter repairs and I certainly have not seen the problem whereby the external screen works and the gpu is faulty.

Anyone else have any input here?

I actually had this exact scenario last year with a Toshiba with a Nvidia GPU. worked on an external but not internal LCD, but still did the same when LCD and inverter were replaced. As it was for a 3rd party warranty company who had set a hard limit on costings, I sent it to Toshiba service center where they could test the motherboard without me having to purchase one. They discovered that it was the motherboard problem, but when I spoke to the tech fixing it , he explained that whilst the GPU controlled internal and external video, that only the circuitry for the internal one was faulty, thus the all ok with an external monitor. I assumed from this ( though he never clarified it) that somewhere between the pinouts on the GPU for the internal LCD and the connector socket for the cable was faulty, though it may have just been the GPU partly faulty , not too sure. But anyhow, hope that sheds light on some questions here.