T400 Issues

[JHake10]

I got a T400 that came in with what appeared to be a dead back light and a dead inverter card. We replaced the LCD and Inverter card and still had the same problem. We then replaced the LCD ribbon cable and still had the same problem. We then replaced the mother board and all the parts and still same issue. The computer boots up and the DVD drive lights up, you can also hook the laptop up to an external monitor and use the computer fine.

Here is where it get interesting. After we tried a new LCD we decided to just take the whole LCD unit off another T400 and put it on the one we are trying to repair. Now that LCD and inverter card have the same issue on out spare T400 model. We though maybe that LCD was also dead it has been laying around for awhile. We take the LCD assembly of out spare T400 which did not work on the laptop we are trying to repair and hook it up to a working T510 and it did not work. So we though that even our spare T400 LCD assembly was not working. We then put the working, previously tested T510 back together and now the T510 back light is dead and the inverter card does not show lights. The inverter card will only show the wireless light when booted up but no other lights such as power, batter or anything.

So basically anything that touches the first computer we are trying to repair seems to catch the same problem. If anybody has any ideas please help.

We tried replacing every part more than once. We also tried taking the battery and CMOS battery out and holding down the power button.

Thank You