Laptop LED screen issue

[coralgol]

Hi
I run into a strange problem. A friend of mine asked me to fix his laptop with broken screen. It`s 17" LED. I replaced it with a new one, but when I turn on laptop the screen seems to go in check mode displaying only grey, white, red, green, blue screen. The screen is filled with one color at a time. No other mumbo jumbo. When I connect laptop to external monitor all is fine but internal LED screen shows only those test screens. I think it`s a bad LED display or should I look somewhere else. Thanks for help.

 

[(*steve*)]

Are you certain that it's an exact replacement? Is it possible one of the connectors isn't connected, or is connected incorrectly? Is there a jumper on the display perhaps to select a test mode?

 

[coralgol]

Hi Steve
I got N173O6-L02 Rev.C1 as a direct replacement for broken screen LP173WD1 (TL)(A1). I checked for any jumpers, there is none. There is only one connector (it is LED), I checked connector on motherboard, all is plugged as it should. Could this be a factory problem? Do they test those diplays before they send them out? I bought it from laptopscreen.com. The old screen was LG , a new one - I have never heard of that company before.

 

[MattyMatt]

Just a quick note, I have bought from laptopscreen.com before, a good bunch of people from what I can tell... and LG = Life is Good electronics, a very reputable name in the LCD/LED/PLASMA line.... and lots of other stuff too... as far as the display goes, I would honestly be looking at the cable that connects the display to the computer.

There are a few questions I have for you though:
1. Did you buy just the bare panel... or the whole screen (with plastics and such) if you bought the whole screen, plastics and all, skip the rest, though there may be a problem within that area.

2. Did you get a cable with the screen or is this the one that was with the Laptop originally (if applicable)

3. Can the cable be inserted (WITHOUT FORCE... very VERY important) any other way with ANY of the other connections (if applicable)

My biggest run in with trouble with these is the "data" connection, its generally small, and it can be broken easily. If you bought just the panel, and did not get a new cable, start from one end of the cable and work your way to the other.... carefully making sure all of the connections are firmly in, and that no EXCESSIVE amount of force is used to get them there... you can also try "Jiggling" the connections a little to see if that changes anything while its powered up, just be careful!

Matty-

 

[coralgol]

Hi Matty

I was thinking about cable too. I have tried to check continuity but the pins on the side that plugs to LED screen are very tiny. I do not have a special probes with fine tips though.
Regarding the panel, Yes , I bought a bare panel (glass with metal frame ). The cable is the one that came with laptop. The cable inserts very nice, just the way it should, No force needed.

I tried to jiggle connections, tap a little the back of the screen where electronic components are but no difference at all.

I will probably send this back to them and wait for replacement of the replacement. If that will not help I will order the cable (China of course , 3 times cheaper than here) but it will take like 3 weeks to get it.

The cable seems to be fine, at least 5 wires that are there and connect webcam. The picture (on external monitor) is great and no distortion of any kind. So I assume the rest should be also OK. There are no spots on the cable that look unusuall. Especially the part where goes underneath the hinge looks good. I am leaning more toward faulty screen, even though it`s brand new from manufacturer.This screen was CHIMEI (did anyone hear about that company) not LG

Cheers

 

[rob_croxford]

Tape some straitend paper clips or something to the end of your probes - this will be fine for checking continuity. Just an idea

 

[MattyMatt]

Never heard of that brand before no... However it seems like you have a pretty good idea what's goin on. I would say you are probably correct with the fault being the actual screen. (at least at this stage)

I would go with what rob was saying, tape something small to the end of your probes (continuity should not be affected). I used to tape staples to the end of my probes before i got some REALLY pointy ones.... which I can no longer find... :-(

Good luck!

 

[coralgol]

Hi

I wanted to make an update and ask more experienced forum users a couple of questions.
I got my replacement screen(second one) at Friday. I installed it and again the same story. But now they sent a screen with a red dot in the center ( it will be sent back again). I started digging internet more with different frazes and I have found this thread
http://forum.notebookreview.com/del...-inspiron-1545-led-screen-no-backlight-2.html

It was for dell inspiron 1545 LED display. Almost the same as mine but 15.6”. Same resolution capability though. In my case the screen lights(back-light OK, no picture at all). So I started checking the motherboard for continuity breaks. And I found 6 similar looking “fuses”. Pardon my expression but they look like resistors too. They also show different resistance reading 277, 256, 72, 9 kOhms.
2 of them are located in the area of battery and HDD slots (continuity OK) and other 4 are located in the area of MB video connector, also close to VGA output. One of those”fuses” PD7 shows NO continuity which leads me to believe this is my problem with display. PD1 up to PD6 pass continuity test. I can not find electric diagram for this motherboard. I uploaded a couple of pictures showing MB with described areas.
Please advise, if from your experience this could be a problem. If yes could this be a beginning to something bigger? My plan is to short it temporary to see if this will help. If I am wrong it will fry my mobo. Any help very much appreciated.



I am still thinking about video cable but after I found this I lean more towards “fuse-resistor” problem.

Cheers

 

[(*steve*)]

OK, a gazzilion things:

1) there is a single file on the board as far as I can see, It is labelled PF1.

2) those other "resistor fuse things" are resistors, capacitors, and other assorted surface mount components. Start shorting them out willy nilly and your laptop may stop working in a permanent way. If it hasn't already... (see next point)

3) You have the board on bubblewrap. The board contains numerous static sensitive parts and you may very well have damaged something due to mishandling.

4) It is pretty clear that the displays you were sent were not the problem per se. It is beyond the realm of probability that 2 units would be suffering the same fault. It is not beyond the realms of probability that you have damaged both of them due to poor handling, or that they are the wrong part, or that your laptop is damaged (see above point).

I would recommend that you reconnect the old screen just to check that the problem that was originally present (and which you haven't detailed) has not changed (i.e. that you have not made things worse).

It would also be useful to see the connectors on the old and new LCD panels, and the locations where they connect to the motherboard.

You are clearly out of your depth.

edit: And furthermore, there is no point trying to diagnose and fix a backlight fault when you tell us that the backlight is working.

Oh, and also, anyone who suggests replacing a fuse with a wire link is not helping you. That entire thread is devoid of anyone remarking on how replacing the fuse with a wire or a ball of solder or a link could send the laptop to the repair house in the sky.

 

[coralgol]

2) those other "resistor fuse things" are resistors, capacitors, and other assorted surface mount components. Start shorting them out willy nilly and your laptop may stop working in a permanent way. If it hasn't already... (see next point)

I put laptop together and it works perfect except internal display. I have disassembled and assembled back laptops and computers countless times and have never ever damaged anything. I have built computers for friends and family. I DO NOT know everything, that is why I am here looking for professional help. If I would go to the specialist I would have to pay 200$ to know what is wrong plus cost of repair. For that money I would have a brand new top model of laptop. So before I go to the ground I do not feel confident I would rather to ask.

3) You have the board on bubblewrap. The board contains numerous static sensitive parts and you may very well have damaged something due to mishandling.

I expected that bubblewrap will make somebody irritated. Yet please do not say I damaged it, as the laptop had this problem before I took it apart.

4) It is pretty clear that the displays you were sent were not the problem per se. It is beyond the realm of probability that 2 units would be suffering the same fault. It is not beyond the realms of probability that you have damaged both of them due to poor handling, or that they are the wrong part, or that your laptop is damaged (see above point).

Another misjudgment, no damage because of handling. I have changed numerous laptop screens (LCD and LED) so you made a wrong assumption. Something is definitely wrong with laptop that is again why I am here.

I would recommend that you reconnect the old screen just to check that the problem that was originally present (and which you haven't detailed) has not changed (i.e. that you have not made things worse).

Nothing new, everything is the way it was before I disassembled laptop. Details: My friend dropped a book on a closed laptop. The screen is smashed badly.Keyboard had a dent in the middle. It is far from where the video connector is. I will upload pictures later.

You are clearly out of your depth.

Because I am asking the questions? Because I used "fuse-resistor" expression? Etc.

Oh, and also, anyone who suggests replacing a fuse with a wire link is not helping you. That entire thread is devoid of anyone remarking on how replacing the fuse with a wire or a ball of solder or a link could send the laptop to the repair house in the sky.

They were not helping me. I came here for help. I consider this forum PROFESSIONAL. Please keep it that way for others. So before I do things I am not sure I seek for professional advice.

Cheers

 

[Resqueline]

I don't know about you but trying to fix a computer MB has me into the deep end, apart from the obvious blown capacitors & fuses one might find.
I see some part designations have a P in front of them, just disregard the P (I don't know why they put it there, perhaps to indicate it's in the power supply section).
You'll find that jumpers = J, fuses = F, resistors = R, capacitors = C, inductors = L, diodes = D, transistors = Q, IC's = U.
I found 3 fuses only, one on each side by the battery connector and one by the VGA connector. There might be more of course.
If you get something like 10 ohms across diodes that's very "suspicious". They may be faulty or there's something they're connected to "shorting" them out.
Likewise, a completely open-circuit diode is faulty, but be sure to check it both ways with the diode range on the DMM.
Inductors are easy to check, they should have a (very) low resistance, but they rarely break.

 

[SeasonedTech]

I don't know about you but trying to fix a computer MB has me into the deep end, apart from the obvious blown capacitors & fuses one might find.
I see some part designations have a P in front of them, just disregard the P (I don't know why they put it there, perhaps to indicate it's in the power supply section).
You'll find that jumpers = J, fuses = F, resistors = R, capacitors = C, inductors = L, diodes = D, transistors = Q, IC's = U.
I found 3 fuses only, one on each side by the battery connector and one by the VGA connector. There might be more of course.
If you get something like 10 ohms across diodes that's very "suspicious". They may be faulty or there's something they're connected to "shorting" them out.
Likewise, a completely open-circuit diode is faulty, but be sure to check it both ways with the diode range on the DMM.
Inductors are easy to check, they should have a (very) low resistance, but they rarely break.

Fact:
If you use an analog meter on its ohms scale to test a good common diode, most will read about 10 ohms in one direction and open in the other.
High speed switching diodes read even less.... about 2-3 ohms.

 

[(*steve*)]

Observation: Using the lowest Vf diodes I have (19A 15V - measures 0.022V at low current), the forward resistance as measured on my multimeters are as follows:

Multimeter A (digital)
200R range = 21.5 ohms
2K range = 40 ohms
20k range = 50 ohms
200k range = 100 ohms

Multimeter B (digital)
200R range = 32.1 ohms
2K range = 34 ohms
20k range = 40 ohms

Multimeter C (analog)
x10 range = 10 ohms
x1000 range = 0

With a slightly more conventional (8A 35V, Vf = 0.15V at low current) schottky diode

Multimeter A (digital)
200R range = 89.6 ohms
2K range = 533 ohms
20k range = 1.23k ohms
200k range = 3k ohms
2000k range = 4k ohms

Multimeter B (digital)
200R range = no reading
2K range = 234 ohms
20k range = 1.9k ohms

Multimeter C (analog)
x10 range = 40 ohms
x1000 range = 1k ohm

And with an extremely bog-standard 1N4001 (50V 1A, vf = 0.561 at low current)

Multimeter A (digital)
200R range = no reading
2K range = no reading
20k range = 19.4k ohms
200k range = 100k ohms
2000k range = 560k ohms

Multimeter B (digital)
200R range = no reading
2K range = 1.434k ohms
20k range = 3.58k ohms
200k range = 20.8k ohms
20M range = 1.03M ohms

Multimeter C (analog)
x10 range = 260 ohms
x1000 range = 13k ohm

So with my multimeters, only a very bizarre diode shows a reading as low as 10 ohms on an analog meter.

This does not mean that SeasonedTech is wrong. However SeasonedTech may have omitted (for simplicity) that because diodes are non-linear devices, and because different meters use different voltages and currents to measure resistances, they will give wildly different readings for the forward resistance of diodes.

If you're going to use resistance ranges to test diodes, then you really need to get a handle on the types of readings you're going to get. A better option may be to use the diode test function (if you have one) as it measures the voltage at some low current. Whilst this current is far lower than would be used for most rectifier diodes (and hence the Vf will appear quite low) it will give far more consistent results between meters (although you might still see significant variation).

So when Resqueline says that a reading of 10 ohms is suspicious for a diode, then I concur. None of my digital meters will give a reading that low on a working diode. My analog meter shows a reading as low as 10 ohms only on a very weird diode.