T61 mobo & LCD woes

[bgalakazam]

I am having problems with my T61 mobo in my T60 15" case. I PM'ed some members who had experience with QXGA, but I am starting to believe the problem is elsewhere, so I am opening this thread.

I have trouble with getting the LCD working on my T61. Currently I cannot get a working LCD in OS mode. Some of the LCDs work in POST and BIOS, others not. I am starting to believe something is wrong with the motherboard or my wiring because I NEVER get the 3 leds (power, battery, hdd) on the T61, no matter which inverter or screen I use. Only the wifi led works. Same inverters on my T60 work with all leds. Here is a bare setup of the T61, CPU, RAM, the long black cable (with or without, doesn't matter), LCD, speaker, keyboard.

Info:
- motherboard 42W7649 (14.1" non-wide, NVS 140M)
- only wifi led works on T61, regardless of inverter
- There is no problem in using external monitor, so GPU is working.
- Speaker beeps work, but you hear a crackling sound when logging in Windows and when shutting down (short somewhere?)
- I have tried testing all possibilities with stock BIOS and Middleton's BIOS. Results are the same, so BIOS is OK.
- I have tried all 3 EDIDs in the complete qxga thread, same results (again, QXGA works like a charm on T60)

Combinations (all tests were done with both 15" LCD cable from T60 and a 14" LCD cable from T61 == same results):

T60 + 15" SXGA+/UXGA inverter (42T0079) + QXGA LCD = POST and BIOS and Windows/Linux LiveCD all work
T60 + 15" XGA inverter (42T0077) + 15" XGA LCD = POST and BIOS and Windows/Linux LiveCD all work

T61 + 15" XGA inverter (42T0077) + 15" XGA LCD = POST and BIOS work, Windows/Linux LiveCD no backlight
T61 + 14" SXGA+ inverter (41W1479) + 14" SXGA+ LCD = POST and BIOS and Windows/Linux LiveCD no backlight
T61 + 15" SXGA+/UXGA inverter (42T0079) + QXGA LCD = POST and BIOS and Windows/Linux LiveCD no backlight
T61 + 15" XGA inverter (42T0077) + QXGA LCD = POST and BIOS work, Windows/Linux LiveCD doesn't work

It is strange that T61 + XGA inverter powers on the QXGA up to OS, but the SXGA+/UXGA doesn't do that.

Can you shed some light? I tried looking if there is a short somewhere, but couldn't find. The LCDs are working fine on my T60. The T61 is flawless when booting on external monitor. The BIOS is stock or Middleton's, no change. I have reset CMOS several times, no change.

Any help would be appreciated as I would like to get my computer up to speed again. Cheers.

[bgalakazam]

Update. When I got the T61, the 14.1" LCD wasn't working. I just tried the same LCD on my T60 and it works.

Seems that the problem is with the T61 motherboard. Again, external has no issue, internal, there is no backlight (read above).

Please advise if I can troubleshoot someway, I don't want to spend another $200 on a new T61 motherboard.

[Totoro-kun]

Good day,
It sounds very much like nVidia defect to me. I have seen many such symptoms in other laptops as well. The analog output (external monitor) works, but LVDS (Laptop lcd, which is on digital source) behaves weirdly. So most likely you will need to get your nvs chip reballed, or to find T61 motherboard with Intel GPU, or go back to the original T60 motherboard, whichever way is more acceptable to you.

As for reballing, it is not always easy to find a good service, and if done poorly, your motherboard will not work for long.

Best regards,
Egidijus

[RealBlackStuff]

Although he nVidia chip is a prime suspect, I would start hunting for (and checking) the fuses near the LCD-cable connector on the mobo. It looks like there is no power coming in to feed the CCFL.
From the above posts, it could also be a faulty LCD cable, which you do no seem to have tried yet.

[bgalakazam]

Same cable same inverters work on my T60. The cables and inverter are good as I tried 4 LCDs, 4 inverters and 3 LCD cables. All work on T60.

I will check the fuses, but by now I have given up and am looking into getting a fix for the GPU.

[RealBlackStuff]

There is no fix for that GPU, other than replacing the motherboard.
Anybody trying to tell you differently is a ??????? artist.
The GPU chip needs to be replaced, end of story.

**DELETED BY dorronto for inappropriate decsriptive word**
**don't want to see this again.........................**

[rssb]

RealBlackStuff is correct, faced the exact same situation where LCD would work on a T60 and T61 base would up up external display but nothing on the LCD. Was the bad nvidia chip, replacing the motherboard is the solution. The video chip has to be changed.

[bgalakazam]

Thank you all for the help.

I am wondering if I should go for the WUXGA T61p or just a plain T61/T61p motherboard. Won't be anytime soon, though.

[beeblebrox]

I am having the same problem at the moment, sitting in front of a mint T61p (WUXGA) with a dead nVidia (which brings only mainboard error beeps on start up).

I switched to another T61 mainboard with Intel X3100 graphics, but I don't get a backlight. Everything else is fine. Can see the Thinkpad logo and Windows, just no backlight.
The seller told me the mainboard was fine and only had a broken LCD.
Is there a T61 fuses layout somewhere, just like the one we have for the T40 series?

I assume a blown fuse.

regards,
Beeblebrox