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Replaced motherboard & inverter, LCD still does not work!

Posted: Thu Oct 13, 2011 1:51 pm
by 996gt2
The LCD on my Thinkpad T61 recently died. I started by ordering a new inverter, since that was a possible cheap fix for the problem. When the first replacement inverter did not work, I tried another one, and the LCD still did not work. Because the laptop outputted fine to an external monitor, I was led to believe (from reading many forum posts online) that the issue may either be with my Nvidia 140M graphics card or with a fuse on the motherboard delivering power to the internal LCD. When I held a flashlight to the LCD, I could not see anything at all (not even a faint display, as would be the case with a bad backlight).

In an attempt to rectify both of those problems, I ordered a brand new system board. The replacement motherboard had Intel graphics instead of NVidia graphics. After I swapped everything in and turned on the computer, the LCD screen briefly worked, but none of the status LEDs on the inverter board worked (except for the Wi-Fi light on the far left). After I turned off the computer and turned it back on, the internal LCD stopped working again.

If I hold up a flashlight to the LCD, I can see a faint image when I boot up. However, once the computer boots into Windows, this faint image disappears even if I shine a bright light at the LCD. This leads me to believe that something may be wrong with the backlight. However, would a bad backlight alone also cause most of the lights on the inverter board to not work? Currently, only the LED for Wi-Fi on the far left works. I'm skeptical that the problem is with the inverter board, since I've tried THREE different inverters (the original one that came with my computer and 2 replacements I bought on eBay). I've inspected the LVDS cable and it does not seem to be damaged. I've also double and triple-checked all of the LCD connections to ensure that they are firmly in place.

What else could be possibly causing the problem here? I was very much encouraged when the LCD worked for a few minutes after I swapped the motherboard, but after that it never worked at full brightness again.

Re: Replaced motherboard & inverter, LCD still does not work!

Posted: Thu Oct 13, 2011 2:30 pm
by rumbero
996gt2 wrote:What else could be possibly causing the problem here?
Have you ever considered the possibilty of a broken LCD? According to my humble experience, the screen is usually more likely to die due to an aging backlight than the inverter. Another possibilty could be a broken LCD cable or cable connector. I would try to find a complete replacement LCD in known working condition.

Re: Replaced motherboard & inverter, LCD still does not work!

Posted: Thu Oct 13, 2011 2:42 pm
by 996gt2
rumbero wrote:Have you ever considered the possibilty of a broken LCD? According to my humble experience, the screen is usually more likely to die due to an aging backlight than the inverter. Another possibilty could be a broken LCD cable or cable connector. I would try to find a complete replacement LCD in known working condition.
I did consider that possibility, but would a broken LCD or broken CCFL cause the status LEDs on the inverter (below the screen) to also not work?

Re: Replaced motherboard & inverter, LCD still does not work!

Posted: Thu Oct 13, 2011 2:50 pm
by Brian10161
I can't remember for certain, but I am pretty certain that the inverter board LED's are powered up by the LCD cable. I changed the inverter in my Thinkpad X60 and IIRC there was only the one cable going into the inverter. I would probably start by getting an LCD from a donor T60/T61.

Good luck!

Re: Replaced motherboard & inverter, LCD still does not work!

Posted: Thu Oct 13, 2011 2:55 pm
by 996gt2
Brian10161 wrote:I can't remember for certain, but I am pretty certain that the inverter board LED's are powered up by the LCD cable. I changed the inverter in my Thinkpad X60 and IIRC there was only the one cable going into the inverter. I would probably start by getting an LCD from a donor T60/T61.

Good luck!
On my T61 there is one connector on the inverter board that connects to part of the LVDS cable, and there is another part of the inverter that connects to the actual LCD panel (to provide power to the CCFLs).

Since the screen does show a dim image, do you think it's reasonable to conclude that the LCD itself is fine and that it's something else (e.g. CCFL) that needs replacement?

Re: Replaced motherboard & inverter, LCD still does not work!

Posted: Thu Oct 13, 2011 8:01 pm
by TuuS
At this point, you can't rule out motherboard, inverter, backlight, lcd or cable. You either need to test them circuit by circuit, which would be cost prohibitive, or substitute known good working parts.

Plug in a known good working lid, if it works, then you know the problem is in your lid. If the substitute lid has the same lcd, then you can swap the parts until you find which is bad. Since you've had so much difficulty, you may find something uncommon, like a bad inverter and cable, or cable and lcd both bad. This isn't common, but since you've replaced the inverter a few times, I'd say you have something unusual going on.

I'd also suspect a mismatch of parts, and with what you've spent, you could have replaced this computer at least once or twice, so get yourself a backup unit and start swapping. Hopefully you'll even end up with two working units. Worse case you have one, and a lot of extra parts that can be swapped in forums like this.

Good luck


ps. As I mentioned in my reply to your PM, I just did an Intel conversion and shipped a really nice working lid back to my customer. I'm sure he'd be happy to sell it if I ask him.He intended on keeping it as a spare, but aside from physical damage (that is common), I don't see many display repairs on these units. Most are system board problems, or the usual ram/harddrive errors. sometimes something more exotic, but I don't recall replacing any displays that didn't have some type of physical or electrical abuse.

Actually, if you feel like spending even more time on this, try putting the original inverter back in.