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Old 11-03-2019, 06:05 AM   #1
caspian
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Default Laptop Screen Compatibility

Dear Forum Members,

Sometimes, I get a number of defective laptops with healthy screens. I have a generic question on finding a compatible laptop screen with LED-backlight.
I know the following items must match to be a compatible screen:
- The same resolution
- The same screen size
- The same connector location
- Pin compatibility on the screen connector
- Screen Type

But I guess some other things may be important too that I do not know. For example, the LVDS version?
Could anyone please clarify what other things must match to be a compatible screen?

Even if a replacement screen is compatible with a different model number, how long is it expected to work on the laptop?
Is it possible that this new screen that has a different model number, fail after a short period due to some hidden incompatibility? (For example, due to weakness of ICs on the screen board)

Thanks

Last edited by caspian; 11-03-2019 at 06:26 AM..
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Old 11-03-2019, 07:23 AM   #2
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Default Re: Laptop Screen Compatibility

The most important thing to look out for is the pinout of the connector. Especially power rails. I've blown up a board by plugging in a wrong panel which shorted out the backlight rail.
Another important thing is the protocol. Either LVDS or eDP.

LCD panels usually live longer than the hardware driving it. They rarely fail if you don't damage or abuse them mechanically.
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Old 11-03-2019, 07:36 AM   #3
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Default Re: Laptop Screen Compatibility

Is it possible that this new screen works fine at first for a while and then it will fail after a month due to some hidden incompatibility between the new and the old screen?
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Old 11-03-2019, 07:50 AM   #4
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Default Re: Laptop Screen Compatibility

I don't think, there may be problems if some signals coming from the motherboard are outside specifications. These problems, in my experience, are very rare. On some types of screens it is possible that the firmware for identification becomes corrupted.
Normally, even on the same notebook model, the manufacturer uses different brands of LCD.

Last edited by jasko_jacker; 11-03-2019 at 07:54 AM..
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Old 11-03-2019, 07:52 AM   #5
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Default Re: Laptop Screen Compatibility

Not really. As long as all voltages are the same. Especially for the backlight. Some screens have the led/ccfl driver in the panel itself with a pwm control line and some have direct connections to the leds like in MacBooks which are driven by a high voltage.

If there is a backlight on & pwm signal on the lvds connector then the panel itself includes the led/ccfl driver. Newer panels only have two connections (anode & cathode) for the led backlight strip. The whole led driver/backlight control is on the mainboard. Those led strips are driven up to 50V which would kill any older panel with an integrated driver. Those usually expect 19V for the backlight and 3.3v for the LCD/logic itself.

Just pay close attention to the pinout and if it's the same you should be fine. But always double check everything.
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Old 11-03-2019, 07:55 AM   #6
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Default Re: Laptop Screen Compatibility

Quote:
Originally Posted by jasko_jacker View Post
I don't think, there may be problems if some signals coming from the motherboard are outside specifications. These problems, in my experience, are very rare. On some types of screens it is possible that the firmware for identification becomes corrupted.
Normal windows laptop usually don't b*tch about the EDID/firmware.
Only apple makes it impossible to replace the screen and remain brightness/color control. Same panel but wrong EDID? Well no backlight control and True Tone for you

Quote:
Originally Posted by jasko_jacker View Post
Normally, even on the same notebook model, the manufacturer uses different brands of LCD.
There are even threads on the internet where people replace the screens to get matte, full hd or even 4k displays in "older" laptops.

Last edited by KvnTM; 11-03-2019 at 07:57 AM..
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Old 11-03-2019, 08:33 AM   #7
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Default Re: Laptop Screen Compatibility

It is possible to replace a LCD with another model and it shouldn't cause long-term issue. I've been replacing panels by random eBay or "local Craigslist" ones, or swapping from other laptops for a long time, and if it works then there's no reason for it to fail because it's not the original one.

Now about compatibility, there are a lot of parameters to look for:
— Dimensions: obviously if you want it to fit correctly you have to chose the same diagonal size, this is often given directly in the model number (eg. LTN156AT32 is a 15.6" LCD). But you also have to look at the actual outer height and width for it to fit perfectly (it's rare but sometimes you have a few mm difference and it won't fit). Also, in some rare cases the thickness can matter too.

— Mountings: if it's a "slim" panel (no metal case all around the panel, circuit board on the bottom protected by black tape), you can have a variety of mounting tabs (none at all, on the side, top/bottom…). If it's a "standard" panel (with metal case all around), you either screw the hinges directly or there are screwable tabs, the screw position should be the same on all panels.

— Protocol: LVDS or eDP (even older panels used TMDS or a custom protocol).

— Channels: 1, 2, 4 channels… linked to the definition, the higher the definition the higher the number of channels required. A 1-channel panel on a 2-channel motherboard should work, but not the opposite. With LVDS, if you use 2-channels panel on 1-channel board, typically the odd columns will be gray. Sometimes you can swap a 1-channel panel to a 2-channel panel (to get higher definition) because the laptop is actually designed to take the 2 definition. The 2nd channel needs to be enabled and routed to the LVDS connector, and the cable has to have the required wires (some rare laptops have 2 different cables for the 2 different definitions available).
Higher number of channels may also mean connector with more pins.

— Bit depth: 6-bit (262k colors) or 8-bit (16.7M colors), rarely matters, on laptops you can typically exchange between the 2. It's relevant on desktop monitors where the panel configuration is programmed statically in the scaler, if you use the wrong type you'll have scrambled image.

— Connector type: there are 2 kinds of connector for LVDS, one with large pitch and one with small pitch with a large latch going all over the connector, typically large pitch is found on CCFL backlight and small pitch on LED backlight. eDP only has one kind as far as I know, similar to the small pitch for LVDS. There are 30 and 40 pins connector (some 20 and 50 pins exist too).

— Connector pinout: pinout is standard, if you match the protocol and the connector type you should have the same pinout. One exception though, the large pitch LVDS on desktop panels has the pinout reversed compared to laptop panels, if you pick the wrong one (desktop panels usually don't fit in laptop but you never know) you can indeed fry the board.

— Connector placement: typically CCFL panels have the connector on top and LED panels have the connector on the bottom. Horizontal positioning can vary so always compare with a picture. Some laptops that are sold with different panel have different cables depending on the connector position.

— Backlight:
CCFL: not used anymore on 2009+ laptops, some desktop monitors used it for a bit longer. Typically the connector is always the same on laptop, on desktop monitors you have a 2 pins (same as on laptop) and a 3 pins (middle pin is not connected). You can also have more than one tube on larger panels.
LED: with integrated backlight driver or external backlight driver. Most laptops use panel with integrated backlight driver, they send the 19V directly to the display. Most desktops have the backlight driver on the mainboard or the power supply board.
None: sometimes you can have panel without the backlight assembly, very rare though. Or OLED, haven't seen one yet so cannot tell you the difference.

— Panel orientation: this is a bit of an odd one and never seen it on laptop, but I had the case of a desktop panel that was addressed "upside-down". No way to know it beforehand, and the original panel was not available, so I rotated the display in Windows, not very good as BIOS was still showing upside-down…

— EDID whitelist: some rare laptops may have a whitelist for panels. Seen that only on a couple of older ones with LVDS, in that case you have to use a panel with very close characteristics (definition, bit depth, refresh rate) and swap (or flash) the EDID ROM chip; it's a 24-series I2C ROM.
While it's not a whitelist, some machines may have the EDID panel configuration statically defined in the BIOS, in that case you also have to use a panel with very close characteristics. It's very rare on laptops, I think some Chromebooks with Coreboot did it… On desktop monitors it's commonly the case as I said earlier, the panel configuration is in the scaler firmware on the mainboard.



There are certain combination of parameters that are extremely common, the 15.6" LVDS panel with LED backlight (integrated backlight driver), 1366x768 definition, "standard" shape (non-slim), connector on bottom left… This is typically used on your low to mid-range 15" consumer laptop from Acer, Toshiba, HP… 2008 to 2014 or something like that. So yeah, those are easy to find and won't cause much trouble, there are loads of different models that are compatible.



And now, Apple: as expected, most of this doesn't apply with Apple panels. You have to use the original panel on Macbooks. Connector and pinout can be proprietary, they use a backlight driver on the mainboard rather than on the panel, panel shape and dimensions aren't like other laptops, they have an EDID whitelist, and you can't even use a 2013/2014 Retina panel on a 2015 Retina even though they have the same characteristics because they decided that backlight should be controlled a bit differently… Same for newer iMac. On old iMac like 2006 models you could swap the panel but it was a bit involving: there is an EDID whitelist so you have to swap the ROM, they used a desktop panel for the 17" iMac so pinout is reversed, it's thicker and has special mountings, and it has 2 CCFL tubes (laptops 17" panels have only one) so you have to connect a dummy tube behind the panel.

Touch panels are another beast, and I haven't had to replace a fused panel yet but if you do, you have to use the original panel as well (since the digitizer is pretty much designed for a specific model). For non-fused panel (where you can separate LCD from digitizer) then you can use another model if it fits properly.
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Last edited by piernov; 11-03-2019 at 08:47 AM..
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Old 11-03-2019, 08:43 AM   #8
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Default Re: Laptop Screen Compatibility

Well that's a comprehensive explanation. Thank you very much for this. That should cover all questions.
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Old 11-03-2019, 08:56 AM   #9
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Default Re: Laptop Screen Compatibility

thanks @piernov and @KvnTM for spending much time on this question. I am reading your posts. I hope I will help you back some day.
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Old 11-03-2019, 09:43 AM   #10
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Default Re: Laptop Screen Compatibility

Quote:
Originally Posted by caspian View Post
thanks @piernov and @KvnTM for spending much time on this question. I am reading your posts. I hope I will help you back some day.
No worries my friend. You already helped me once or twice
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Old 11-03-2019, 12:07 PM   #11
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Default Re: Laptop Screen Compatibility

Quote:
Originally Posted by KvnTM View Post
Well that's a comprehensive explanation. Thank you very much for this. That should cover all questions.
+1 .Thread stickied .
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Old 11-04-2019, 04:21 AM   #12
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Default Re: Laptop Screen Compatibility

Some Acers will boot (at least 6530G did) with different size screens. My 6530G had a broken Samsung 16" CCFL panel, but plugging in a 15.4" screen worked and I had a clear picture. (main NB died on it after a few hours, now I'm going to order a 6930G board + cooler so I can finally steer clear of AMD chipsets)
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Old 11-04-2019, 04:39 AM   #13
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Default Re: Laptop Screen Compatibility

thanks, this is a useful topic too:
Connecting a laptop to a pin-compatible screen with a different screen size

this is useful when we want to test a laptop using a different-size screen where we do not have a same-size screen.
It would be great if members share their experiences in such situations.
Does connecting a laptop to a pin-compatible screen with a different screen size cause any damage after a while?
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Old 11-04-2019, 05:12 AM   #14
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Default Re: Laptop Screen Compatibility

Quote:
Originally Posted by caspian View Post
thanks, this is a useful topic too:
Connecting a laptop to a pin-compatible screen with a different screen size

this is useful when we want to test a laptop using a different-size screen where we do not have a same-size screen.
It would be great if members share their experiences in such situations.
Does connecting a laptop to a pin-compatible screen with a different screen size cause any damage after a while?
Not really. At least my 6530G (soon to be 6930) worked fine with a 15.4 LCD but wouldn't fit into the case. Thing is you will need to match the manufacturer. In my case the shattered screen was a Samsung, and the good 15.4 LCD was a Samsung too. Interestingly, a 15.6 AU Optronics did work as well, but the backlight would shut off as soon as the BIOS splash screen would appear.
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Old 11-23-2019, 07:01 AM   #15
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Default Re: Laptop Screen Compatibility

good/bad experiences on the following topic are welcome:
"Connecting a laptop to a pin-compatible screen with a different screen size"
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Old 11-25-2019, 12:05 AM   #16
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Default Re: Laptop Screen Compatibility

Quote:
Originally Posted by piernov View Post
It is possible to replace a LCD with another model and it shouldn't cause long-term issue. I've been replacing panels by random eBay or "local Craigslist" ones, or swapping from other laptops for a long time, and if it works then there's no reason for it to fail because it's not the original one.

Now about compatibility, there are a lot of parameters to look for:
— Dimensions: obviously if you want it to fit correctly you have to chose the same diagonal size, this is often given directly in the model number (eg. LTN156AT32 is a 15.6" LCD). But you also have to look at the actual outer height and width for it to fit perfectly (it's rare but sometimes you have a few mm difference and it won't fit). Also, in some rare cases the thickness can matter too.

— Mountings: if it's a "slim" panel (no metal case all around the panel, circuit board on the bottom protected by black tape), you can have a variety of mounting tabs (none at all, on the side, top/bottom…). If it's a "standard" panel (with metal case all around), you either screw the hinges directly or there are screwable tabs, the screw position should be the same on all panels.

— Protocol: LVDS or eDP (even older panels used TMDS or a custom protocol).

— Channels: 1, 2, 4 channels… linked to the definition, the higher the definition the higher the number of channels required. A 1-channel panel on a 2-channel motherboard should work, but not the opposite. With LVDS, if you use 2-channels panel on 1-channel board, typically the odd columns will be gray. Sometimes you can swap a 1-channel panel to a 2-channel panel (to get higher definition) because the laptop is actually designed to take the 2 definition. The 2nd channel needs to be enabled and routed to the LVDS connector, and the cable has to have the required wires (some rare laptops have 2 different cables for the 2 different definitions available).
Higher number of channels may also mean connector with more pins.

— Bit depth: 6-bit (262k colors) or 8-bit (16.7M colors), rarely matters, on laptops you can typically exchange between the 2. It's relevant on desktop monitors where the panel configuration is programmed statically in the scaler, if you use the wrong type you'll have scrambled image.

— Connector type: there are 2 kinds of connector for LVDS, one with large pitch and one with small pitch with a large latch going all over the connector, typically large pitch is found on CCFL backlight and small pitch on LED backlight. eDP only has one kind as far as I know, similar to the small pitch for LVDS. There are 30 and 40 pins connector (some 20 and 50 pins exist too).

— Connector pinout: pinout is standard, if you match the protocol and the connector type you should have the same pinout. One exception though, the large pitch LVDS on desktop panels has the pinout reversed compared to laptop panels, if you pick the wrong one (desktop panels usually don't fit in laptop but you never know) you can indeed fry the board.

— Connector placement: typically CCFL panels have the connector on top and LED panels have the connector on the bottom. Horizontal positioning can vary so always compare with a picture. Some laptops that are sold with different panel have different cables depending on the connector position.

— Backlight:
CCFL: not used anymore on 2009+ laptops, some desktop monitors used it for a bit longer. Typically the connector is always the same on laptop, on desktop monitors you have a 2 pins (same as on laptop) and a 3 pins (middle pin is not connected). You can also have more than one tube on larger panels.
LED: with integrated backlight driver or external backlight driver. Most laptops use panel with integrated backlight driver, they send the 19V directly to the display. Most desktops have the backlight driver on the mainboard or the power supply board.
None: sometimes you can have panel without the backlight assembly, very rare though. Or OLED, haven't seen one yet so cannot tell you the difference.

— Panel orientation: this is a bit of an odd one and never seen it on laptop, but I had the case of a desktop panel that was addressed "upside-down". No way to know it beforehand, and the original panel was not available, so I rotated the display in Windows, not very good as BIOS was still showing upside-down…

— EDID whitelist: some rare laptops may have a whitelist for panels. Seen that only on a couple of older ones with LVDS, in that case you have to use a panel with very close characteristics (definition, bit depth, refresh rate) and swap (or flash) the EDID ROM chip; it's a 24-series I2C ROM.
While it's not a whitelist, some machines may have the EDID panel configuration statically defined in the BIOS, in that case you also have to use a panel with very close characteristics. It's very rare on laptops, I think some Chromebooks with Coreboot did it… On desktop monitors it's commonly the case as I said earlier, the panel configuration is in the scaler firmware on the mainboard.



There are certain combination of parameters that are extremely common, the 15.6" LVDS panel with LED backlight (integrated backlight driver), 1366x768 definition, "standard" shape (non-slim), connector on bottom left… This is typically used on your low to mid-range 15" consumer laptop from Acer, Toshiba, HP… 2008 to 2014 or something like that. So yeah, those are easy to find and won't cause much trouble, there are loads of different models that are compatible.



And now, Apple: as expected, most of this doesn't apply with Apple panels. You have to use the original panel on Macbooks. Connector and pinout can be proprietary, they use a backlight driver on the mainboard rather than on the panel, panel shape and dimensions aren't like other laptops, they have an EDID whitelist, and you can't even use a 2013/2014 Retina panel on a 2015 Retina even though they have the same characteristics because they decided that backlight should be controlled a bit differently… Same for newer iMac. On old iMac like 2006 models you could swap the panel but it was a bit involving: there is an EDID whitelist so you have to swap the ROM, they used a desktop panel for the 17" iMac so pinout is reversed, it's thicker and has special mountings, and it has 2 CCFL tubes (laptops 17" panels have only one) so you have to connect a dummy tube behind the panel.

Touch panels are another beast, and I haven't had to replace a fused panel yet but if you do, you have to use the original panel as well (since the digitizer is pretty much designed for a specific model). For non-fused panel (where you can separate LCD from digitizer) then you can use another model if it fits properly.
great explanation!
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