Thinkpads Forum

I need to examine some laptops, (t400 or t500), I am looking to get one with 1280x800 LED screen.

How can i know, using software which back light type is used ?

I will be able to run either windows or linux from usb.

Use the serial number and first 4 MTM digits, to check on the partslist ex-factory: https://support.lenovo.com/us/en/partslookup
Then with the help of the HMM you can see what's in there.

If you've got the PCs in front of you, you can also use PC-Wizard to get the LCD model number which you can look up to get specifications on.

Thanks for the replies.

Looking up the parts is great and much easier than anything else, but it doesn't look 100% consistent.
I looked up a few random serial numbers for T400's from ebay, some do not have the part number of either the LED subcard or the inverter, which is not possible, ..

and some parts are listed without FRU and only "Mfg P/N".

but, the few laptops i looked up, i was able to identify which backlight it have, either by the subcard or the screen itself.

but as an extra measure, i think i still need a software solution to verify that it correct..

There is another option but it's not a software solution. You would need to have physical access to the laptop, it must power up to at least the BIOS menu and the backlight must be working (brighten and dims with Fn+Home/End). From your initial post where you say you can boot the system with Windows or Linux, implies to me that all of these conditions can be met. The last piece of this checkout procedure is that you need a small neon lamp (a typical one has a part number of NE-2).

A screen which has a CCFL must also have an inverter board to drive the lamp. That inverter board generates a high voltage that will cause a neon lamp to glow simply by being placed near the output connector of the inverter board. You don't even have to remove the plastic screen bezel. The screen should be set to the maximum brightness and then you should see this effect if the LCD panel uses a CCFL like here:

<-- click for larger image (1024x768; 74KB)

A screen that uses LED backlighting will not have an inverter board and therefore the neon lamp will not light up. You will have to move the neon lamp around the right corner of the LCD bezel (typically where a CCFL backlight would plug into an inverter) to ensure that you don't miss the inverter output. I can say that if the neon lamp does light up, then that screen must be using a CCFL. I've tested this out on an A31p, a T60p and a W500. All lit the neon lamp. An X300, X301, T410 and T420 did not.

AIDA64 or various utils like that.

You get something like this: LTN141BT09001

then google the panel

http://www.laptoplcd.de/samsung-ltn141b ... -4419.html

@TonyJZX,
Thanks.

rkawakami wrote:The last piece of this checkout procedure is that you need a small neon lamp (a typical one has a part number of NE-2).

Great suggestion,
after reading your post, i started searching what could have a small neon lamp, and i did find that i have a couple of "Electric Mains Testing Screwdriver", and those have neon lamps in them.

I will have to read a bit more about this, but do you know whether i have to short circuit the lamp as the image you posted, or can i just use the screw driver as-is ?

No, you do not have to short the leads together on the lamp for this to work. I did that only because it was easier to hold and I wasn't sure if there would be any voltage/current potential across the leads .

What you do have to do is get the lamp as close as possible to the bezel. From what I recall of those mains voltage testers, the lamp is probably about 2 or 3mm from the outside edge of the plastic case (or more). That could be enough to prevent it from working as a inverter detector. If you can get you hands on just a loose neon lamp, that would be best. An electronics surplus store can be a source, along with old appliances that used them as power indicator.

RealBlackStuff wrote:Use the serial number and first 4 MTM digits, to check on the partslist ex-factory: https://support.lenovo.com/us/en/partslookup
Then with the help of the HMM you can see what's in there.

Thanks, that systematically solves a number of riddles I run into with my machines.

Good advice is more valuable than gold.

At this rate we're buying relatively unknown 2nd hand units from IT exlease companies and the like and IMO, T400s have gotten to be pretty much worthless.

I seen a heap of units go for under $50... ie. complete working units with no HDD no charger but with the ram etc.

Just add a cheap 120Gb SSD, install Win7, run a loader and you got a fine machine.

However for T400s, I've seen 50/50 for CCFL vs LED. I dislike CCFL, the colours just look faded.

And Core 2 Duo is pretty much done as far as Windows goes. I find a marked improvement in performance from a fast C2D to a base i5 Arrandale and the T410s I see are around $75 so to me the saving isnt there.

ie. may as well get a T410 w/ 1,440 x 900 LED screen for a little more.

Hell, T420s have gotten into the same price category. Under $100 for a diskless T420, too bad about the 768p screen which I find deplorable.

However I do see T420s and the occasional T420 w/ 900p screen for under $100 so you may grab those if you're lucky.

rkawakami wrote:No, you do not have to short the leads together on the lamp for this to work. I did that only because it was easier to hold and I wasn't sure if there would be any voltage/current potential across the leads .

What you do have to do is get the lamp as close as possible to the bezel. From what I recall of those mains voltage testers, the lamp is probably about 2 or 3mm from the outside edge of the plastic case (or more). That could be enough to prevent it from working as a inverter detector. If you can get you hands on just a loose neon lamp, that would be best. An electronics surplus store can be a source, along with old appliances that used them as power indicator.

I have just tested this,

had to disassemble the screwdriver to extract the lamp, because the screw driver as a whole did not work.

and, .. with the lamp only, it worked like a charm tested on an old HP laptop only though.

I have also noticed that changing the screen brightness while holding the lamp result in the lamp getting equally affected by brightness change, was quite interesting.

Thanks for your help !

In linux 'dispcalGUI' will (usually) tell you the model of the display is being used.
With that you can search the web and quickly figure out details about the display, such as led/ccfl.

This is simpler: See https://libreboot.org/docs/misc/index.h ... _panelname