T400 motherboard replacement advice needed? [ Edited ]

[VenkatReddy]

i have a T400 2764cto model thinkpad bought 2 years back with following config

Intel® Core™ 2 Duo Processor P8700 (2.53GHz)
Windows 7 Professional
14.1 WXGA TFT, w/ LED Backlight, Camera
ATI Mobility Radeon 3470 with 256MB
4GB DDR3
UltraNav (TrackPoint and TouchPad) with Fingerprint Reader
Express Card Slot & 7-1 Media Card Reader
250 GB Hard Disk Drive 5400rpm
DVD Recordable 8x Max Dual Layer, Ultrabay Slim (Serial ATA)
Integrated Bluetooth PAN
Intel Wifi Link 5300
9 cell Battery (replaced it in aug 2011)

Suddenly i lost the display (but works with external monitor) when sent to service center they say that motherboard got damaged and need to be replaced and also bluetooth.

NOTE: dont have any other problem other than above ones

SO

is it better to get the motherboard replaced? which they say costs about 500 USD (and 50 USD for bluetooth)

thanks for your thoughts

[VenkatReddy]

updated above...

[vnn1206]

May be there are problem with your hight voltage board or lcd panel.

[Wendel]

If the external monitor works and everything else works, how can they say it's the motherboard? If the external monitor didn't work either, then I can see the problem being the graphics chip and you'd need a new MB. I would look from the LCD connection on the MB to the LCD display itself for the problem.

[richk]

The graphics chip has 2 separate outputs - one for the LCD and one for external.  Also, there is a fuse on the MB that controls the backlight.

[kaplac]

Sorry to revive an old thread, 

Do you know where I can find the fuse for the backlight? 

I have a feeling I might have blown mine and I'd rather not pay several hundred dollars for a replacement.

[richk]

Check the one labled F7 (usually has a "P" on it) near the side of the LCD connector closer to the optical drive. The board uses lead-free solder which melts at a VERY high temperature. You cannot change it without a good rework station.  I just saw your other post which said no lights also.  You should also check another smaller fuse, which usually is not labled.  It is also next to the LCD connector, nearer to the CPU.  It should be blue or green.  They can blow at the same time and can be caused by a bad or the wrong inverter

[jack135]

My T400 just got same problem. LCD is blank, only faint Lenovo logo visible during bootup, then hardly can see anything on LCD screen. No LED indicator is on either, except the wireless LED. Power setting not working either, so the close lid power function is not working as it supposes to.

But when I connect to external monitor, it works. However, I can't see dual monitors display option any more, only external monitor is detected.

There is another thread saying it could be the switch that detects if the lid is closed not working, but it doesn't explain the LED lights not working either.

Anyone has any idea what happen? and how to repair it?

Thanks

[richk]

If the backlight does not come on AND the indicators on the screen (power, battery, etc) don't come on, my guess is that 2 fuses on the motherboard are blown.  Lenovo does not do that sort of repair

[laptopfixer]

Does anyone know the value/specs of these two fuses? I would like to try to repair one of these motherboards.