LCD screens- way to test?

[Jesse Kosalka]

When diagnosing a laptop with screen issues, it can sometimes be difficult to discern the cause (apart from obviously cracked screen). It either ends up being the LCD screen, the cable, or the motherboard, and a misdiagnosis is always bad for the customer and our bottom line.
In an attempt to cut down on misdiagnoses, I was hoping there would be a better way to test the components. I have always had bad luck with keeping good screens around to test with- even if a screen has the same connector, it doesn't always mean it will be compatible and can sometimes cause more damage. So spare screens for testing seems to not be an option.

So I came across this on eBay- a device to test LCD screens.
http://www.ebay.com/itm/LCD-Screen-Tester-LST04-How-to-test-Laptop-Screen-/401080352503
Does anyone have any experience with these devices? Are they reliable? Worth the price?

Any better options?

Thanks

 

[NETWizz]

Honestly, I just plug in an external LCD and check if it works. If it works and the screen on the laptop doesn't, I figure it needs replacement. Thus far this has worked well and not been wrong though I guess it is possible the motherboard would deliver output to an external screen and not an internal screen.

 

[Larry Sabo]

@NETWizz, if the fuse near the LVDS connector (or inside the LCD) is blown, you would still get video on an external monitor but not on the laptop screen. Well, you would get video but no light, so that's not definitive. When I get no video on an external or internal screen, I'm never confident that video switching is taking place using F + {something} keys. Swapping in a known good screen is an infallible test, IMHO.

This LCD tester would probably do the job but it's $240 USD and a little complicated, I think.

 

[NETWizz]

@NETWizz, if the fuse near the LVDS connector (or inside the LCD) is blown, you would still get video on an external monitor but not on the laptop screen. Well, you would get video but no light, so that's not definitive. When I get no video on an external or internal screen, I'm never confident that video switching is taking place using F + {something} keys. Swapping in a known good screen is an infallible test, IMHO.

This LCD tester would probably do the job but it's $240 USD and a little complicated, I think.

I have had an inverter board burn out on a previous laptop once, but like you said the screen was simply dark in that the CCFL did not light. Yeah, now I am pretty certain most are probably LED.

 

[Jesse Kosalka]

@NETWizz, if the fuse near the LVDS connector (or inside the LCD) is blown, you would still get video on an external monitor but not on the laptop screen. Well, you would get video but no light, so that's not definitive. When I get no video on an external or internal screen, I'm never confident that video switching is taking place using F + {something} keys. Swapping in a known good screen is an infallible test, IMHO.

This LCD tester would probably do the job but it's $240 USD and a little complicated, I think.

I'm curious about your experiences with swapping in known good screens. Do you just keep a stock of all different types and sizes? There seems to be a such a variety of connector types.
Even if you have a known good screen with the same connector as the broken one, is there something that can still make it incompatible? Do certain sizes of screens need a certain type of cable?
My first experience with swapping in a known good screen happened when I used a screen with the same connector, and after powering on the computer, it started sparking near the connector, so that pretty much scared me off from doing that again.

 

[Larry Sabo]

@jesse, I've only done it a few times but haven't had any unpleasant collateral damage. (I'm a small home-based shop, not a store front.) Usually, I have some defective screens that still show a partial image, or at least light up if the screen shows no image. For CCFL screens, I have a tester that illuminates the screen if it or the inverter is not burned out but as @NEWTWizz says, most screens are LCD now so it rarely gets used any more.

I don't stock commonly used screens because they end up sitting around forever, but there is a thread on TN of which screens are most popular and worth stocking. If I did, I'd probably use one of them. Too bad about your rotten luck with that screen zapping something but I know of no way to know whether that might happen with any give test screen. I'm sure the major screen distributors like laptopscreens.com have a program that could tell you whether the test screen will be compatible with a given make/model laptop but that's no accessible to us, unfortunately.

Sorry, but I don't know what the odds are that if the connectors are compatible, the cable pinout and voltages will be also.

Edit: If the part number on the back of the test screen is the same as on the back of the laptop's screen, they would be compatible, of course.

 

[Krynn72]

Right now there seems to be about 4 different types of common screens. We stock a "standard" 15.6" screen, a "standard" 17" screen, a "slim" 30-pin, and a "slim" 40-pin. I'd say 9/10 laptops will use one of these. Most of the time you can at least test with one of these screens even if its not the same one, or even the same size. You need to make sure its the same connector though, which again there's usually only a few different styles.

These days you also need to check if they're FHD(1080p) or regular HD, etc. But again, you can test to see if a FHD screen is bad with a normal HD one with the same connector.