T43 screen replacement trouble

[cbarnaby]

Problem: T43 with cracked SVGA+ LCD display. Worked OK w/ external monitor.

Bought and installed allegedly direct replacement LCD.

After replacment, system will not power up. Starts for a few seconds, then shuts down.

Re-installed original LCD. Same symptom.

Works OK with external monitor.

Details --

ThinkPad: 2668W12

Original LCD: IBM P/N 92P6736; FRU P/N 92P6737

Replacement LCD: Quanta QD14FL07

What did I blow out?? Any suggestions appreciated.

[Troels]

The QD14FL07 is not an original part for the T4x series, Quanta actually never was a part supplier as far as i know.

Before you uninstalled the cracked LCD, did it boot up correctly - although with a screwed up image?

Make sure that the LCD cable is intact - it is easy to break it just slightly at the 90 degree joint between the flex cable that goes to the lcd and the flex cable going to the inverter.

There's no beeps of any sort when booting up?

And welcome by the way!

[sjthinkpader]

The 5V and GND pin assignment on the T43 SXGA+ panel is different from others. A fuse may be blown by connecting a different LCD.

Some manufacturers have different pinouts even with same part number. You have to match the panels to the dash numbers.

[cbarnaby]

Yes, the machine started OK with the cracked panel before I installed the replacement.

There are no beeps. The shutdown occurs in perhaps 3 - 5 seconds (very quick). With the external monitor plugged in, startup is normal.

Do speaker settings suppress startup beeps? Perhaps I should start with the external monitor and make sure sound is working OK, then retry.

I will check cables and pinouts, but probably not until next weekend.

Thanks.

[cbarnaby]

I have checked things over, no obvious problems.

Connectors on the Quanta LCD seem compatible with the cables.

If something, such as a fuse, was blown by installing the Quanta screen ... where would that be? It is clearly not in any fundamental place, since the system runs OK with an external monitor.

How does does one determine if the Quanta screen is electrically compatible with the T43? It was sold to me as an acceptable replacement for the 92P6736, but there is obviously some question about that. The resolution specs match (SXGA+, 1400 x 1050). On the Quanta label it says "Rating 3.3V 1200 mA; Inverter rating 9-21V, 590 mA". Does that mean anything to anyone?

[oddb@ll]

did you change the inverter?

[cbarnaby]

I did not replace the inverter.

I talked to the vendor (LapZone) that sold me the Quanta LCD screen.

They insist that the Quanta screen is a direct replacement for the IBM original. So in theory, no reason to replace the inverter. Before I started, the cracked LCD screen still lit up, so that would indicate the inverter was OK, right?

Assuming that the LCD is compatible, the conclusion is that the non-startup symptom was caused by an installation error on my part.

What can cause the non-start symptom? If the LCD is in fact an OK replacement part, it should work if I figure out how to fix the non-start problem. As I said, the system starts OK with an external monitor, so the problem is somewhat localized.

[NathanA]

I talked to the vendor (LapZone) that sold me the Quanta LCD screen. They insist that the Quanta screen is a direct replacement for the IBM original.

They are WRONG, and their mistake has cost you the LCD controller chip on your T43's motherboard.

See these posts, and the links to other posts off of them (esp. the second one...pics of the chip in question):

http://forum.thinkpads.com/viewtopic.php?t=49648
http://forum.thinkpads.com/viewtopic.php?t=48776
http://forum.thinkpads.com/viewtopic.php?t=57332
http://forum.thinkpads.com/viewtopic.php?t=19825

Some LCDs have subtle differences in pinout between closely-related models (for example, Samsung LTN141P4-L02 [IBM] vs. LTN141P4-L01 [Non-IBM], or IDTech IASX16S [IBM] vs. IASX16C [Non-IBM]), and based on other peoples' experiences using the non-IBM versions of these displays, even though the connector on the end of the ribbon cable will physically mate to the screen does NOT mean that it will work.

In fact, as you can see from reading some of the above posts, plugging in a non-IBM LCD into a ThinkPad actually causes irreversible damage to a component on the mainboard (LCD controller chip). This is why your computer will not boot unless it has an external display it can default to. It won't matter whether you get the correct LCD replacement now because the motherboard is toast and will need to be replaced (unless you have a place that you can source the controller chip from and are REALLY handy with a soldering iron!).

In your case, it wasn't even a matter of whether you got sent the correct "version" of a supported display; Quanta was NEVER an LCD vendor for IBM/Lenovo. You can verify this yourself by downloading the Hardware Maintenance Manual for the T43 and looking at the FRU list. Looking up your model number (2668-W12) tells me that you have a 14" T43; you can see the parts list information for 14" LCDs here:

http://www-307.ibm.com/pc/support/site. ... 58431.html

Note that for the 14" SXGA+ screen on the T43, the only vendors mentioned are BoE-Hydis and Samsung. Quanta is nowhere to be found, and I've never heard of a single T4x or T6x model ever shipping with a Quanta screen.

The guys at the place you bought your screen from are incompetent morons, I'm afraid. I would take this problem back to them and make it their problem. Hopefully they will do the responsible/honorable thing and make it right.

For future do-it-yourself LCD replacement projects, unless the computer is one you are willing to sacrifice for the sake of science , I would make a point of only purchasing LCDs with an IBM FRU sticker on them (although it is possible to get lucky sometimes).

Good luck,

-- Nathan