ThinkPad T42 - XGA LCD upgrade to SXGA+ problem

[need4speed]

Hi!

I have a ThinkPad T42 which is born of 1024x768 XGA 14.1" LCD Panel. Recently I decided to upgrade the screen to SXGA+ so I purchased a refurbished SXGA+ LCD Panel Samsung LTN141P4-L02 (aka FRU 11P8348) off E-Bay. I wanted to buy an original IBM LCD Cable Assembly (FRU 91P6787) but could not find one locally where I am staying, so instead bought a third party compatible SXGA+ LCD cable (as claimed by the seller) from a local store. I retained my existing inverter board (FRU 26P8464) as the T42 HMM stated that this part is the same for both XGA and SXGA+ models. When I connected up the Samsung SXGA+ LCD Panel using the third party compatible LCD cable and my existing inverter board, the display did not show any image when the laptop was powered up.

Strangely I also noticed that the backlight of the SXGA+ Panel did not seem to turn on when I powered up. I am very sure that the 2-wire connection to the inverter board is properly made and can confirm that the LCD Cable is correctly connected from the mainboard to the data socket behind the LCD Panel as well as to the chip on one end of the inverter board. The ThinkLight can also turn on/off when I toggle Fn+PgUp.

As the new display did not work, I connected back my old XGA LCD Panel and everything worked like it used to!

I am speculating the following:

1) The SXGA+ LCD Panel that I bought off E-Bay was outright faulty.

2) Assuming the SXGA+ LCD Panel is good, then the non-original SXGA+ LCD Cable may be the culprit. However as my inverter board is definitely proven working and its sole purpose is to light up the CCFL in the LCD Panel, I should at least see the backlight turn on in the SXGA+ LCD Panel when it was connected, shouldn't I? Unless of course the SXGA+ LCD Panel was also screwed in the first place as it was bought off E-Bay.

3) Interestingly I connected the non-original SXGA+ LCD Cable to my old XGA Panel and it worked too! In fact I am now typing away on the T42 with the supposedly SXGA+ LCD Cable connecting my old XGA screen. So this led me to wonder if the LCD Cable is actually an XGA Cable but wrongly sold to me by the store as a SXGA+ Cable? Or is the SXGA+ Cable actually capable of driving both XGA and SXGA+ screens (even though technically the HMM stated different FRU# for the LCD Cable of both models)?

While there is a chance that the SXGA+ LCD Panel that I bought is faulty, I am more inclined to buy an original LCD Cable to confirm. What do you guys think the problem may be? Any opinion and advice will be greatly appreciated.

Also I stay in Singapore (Asia) and as I said earlier that I could not find the original LCD Cable locally. Can someone advise a reliable online source to buy the LCD Cable who provides international shipping to Singapore?

Many thanks in advance!

[Harryc]

I'd try another LCD signal cable. International shipping with 91P6787 in stock -

http://www.notebookpartsforless.com/servlet/StoreFront
http://cgi.ebay.com/For-IBM-T41-T42-T40 ... 0403498432
http://cgi.ebay.com/New-14-1-LCD-Video- ... 0095230698

[need4speed]

Thanks for your reply mate.

Would you think that I should change to a new inverter board (FRU 26P8464) as well since I noticed that my existing inverter didn't seem to fire up the CCFL in the SXGA+ LCD when connected, even though everything worked perfectly when I hook back my old XGA screen? Could it be a case of insufficient juice?

[need4speed]

Also has anyone bought stuff from www.thinkpad-parts.com before?

Anyone knows if they carry original IBM / Lenovo 91P6787 and 26P8464? How's the buying experience with them?

I read that they ship internationally via FedEx, UPS and DHL, so wondering if I will be able to receive the items within 3 business days upon order. I guess I can email them to find out but if anyone has any experience to share I'd be glad to know.

Thanks.

[Harryc]

My opinion is that if the inverter works with the XGA setup then it is not the issue with the SXGA+ setup not lighting up. Could still be a faulty new SXGA+ LCD panel though, or the cable.

[need4speed]

I could be wrong, but my guess is that if the non-original SXGA+ cable can supply enough juice thru the inverter circuit to light up my old XGA panel, it should therefore be able to at least light up the CCFL in the new SXGA+ panel. Unless the input voltage to drive the XGA panel is different from the SXGA+ panel.

I am just applying my engineering knowledge to some good use here, but well as I said, I could be wrong......

In any case my next step will be to get an original LCD cable and test again. I'd welcome any further insight.

[Harryc]

Well, use your skills to good advantage. The bottom line is that there are only (3) parts at play here. The LCD assembly, the cable, and the inverter. Feel free to swap all three There are no 'tests' for these parts if they are defective, unless you have another donor machine to swap things into.

[richk]

The 14" T4x machines use a non-standard connection. You really need to use a panel with the right FRU.

[91011]

I think #3 is the most likely reason.

3) Interestingly I connected the non-original SXGA+ LCD Cable to my old XGA Panel and it worked too! In fact I am now typing away on the T42 with the supposedly SXGA+ LCD Cable connecting my old XGA screen. So this led me to wonder if the LCD Cable is actually an XGA Cable but wrongly sold to me by the store as a SXGA+ Cable?

From personal experience with T30 machines, an XGA cable would not drive an SXGA+ LCD and an SXGA+ cable would not drive a XGA LCD. Totally black screen with the wrong cable.
No reason to doubt the would T4x would not be similar. They do have different FRU numbers, as did the T30 cables.

T4x cables:
XGA: 91P6786
SXGA+: 91P6787

John

[systemBuilder]

Are you certain that a SXGA+ panel can work with a limited ATI 7500 chipset? I studied all the graphics chips in the T4x series before making a purchase, and the SXGA+ models all seem to use an ATI 9000, 9600, FireGL, or X300 chipsets. I replaced our hydis SXGA+ display (broken) with a samsung display, and it worked fine, but I am not certain my laptop could recognize even an XGA panel, as the ATI 9600 drivers might be specific to a particular size of panel.

[sktn77a]

Yes, the sxga+ screen works fine with the ATI7500 GPU.

[need4speed]

Yes I am quite positive that the ATI 7500 GPU can drive an SXGA+ panel as I can confirm from a mate who uses a T42 on the same GPU but on SXGA+.

At this moment, I tend to agree that the LCD Cable integrity is the biggest suspect and is placing my bet on this (at least for now). I have already placed on order at http://www.thinkpad-parts.com and looking forward to receiving the cable. I have requested International Overnight shipping and is awaiting their confirmation on shipping cost (they resume business on Monday morning). Does anyone have some sort of experience as to how much international overnight shipping may cost me?

I am still trying to understand if the different LCD Cables (XGA vs SXGA+) actually drive the CCFL in both screens differently. I am thinking that the output thru the inverter into the CCFL should be quite standard.

[91011]

Yes, a 7500 will work with an SXGA+ LCD. I did the swap last week.

IBM even shipped a few with that combo:
2378-R5U
2379-R5U

John

[need4speed]

I came across an interesting article on http://therning.org/niklas/2009/05/fixi ... nkpad-r32/. Specifically I am referring to the section that talked about updating the inverter EEPROM whenever an LCD replacement occurs, but that is for the ThinkPad R32.

Having gone thru lots of information on the T42, I am quite convinced that this procedure does not apply to the T42. Can someone confirm?