Thinkpads Forum

I'm troubleshooting a dead T-400 and was wondering if a good board will normally boot with only an external monitor connected? Assuming I have some memory installed, keyboard connected and a good source of power. I wanted to eliminate the LCD and cable as a possible source of trouble that's why I'm asking. I'm hoping/expecting to find a blown fuselink on the mainboard (anybody have a pic for fuse locations?) Thanks
Mark in Mt. View, Ca

Yes, it will boot normally with no (or external only) displays attached.

Fuses are normally marked with "F", "FU" and etc. There are different kinds of fuses. You also need a multimeter with function continuity test/diode test - this is how you can check the status of the fuse. This is as much as I can help you, because I don't have the schematic for the fuses in T400.

Welcome to thinkpads.com (Howdy neighbor; I grew up in Mtn. View)!

I would try powering up the system with all of the main hardware removed; all memory, hard drive, Ultrabay drive, PCIe cards, modem daughter card. Leave the CPU, heatsink, keyboard and speakers connected. If the system does attempt to boot, you should hear the 1-3-3-1 beep code. That would at least give you some indication that the motherboard is somewhat okay. If the system does power up and beep, then whatever you removed may be keeping the system from powering on. Power off, replace one item and try powering up again. I would start with one memory module so you can at least see any system activity on the external monitor. You might have to press the Fn+F7 key combination to get the VGA port to output a signal.

If there is still no indication of the board receiving power when all of the hardware was removed, then a close examination of the motherboard is in order. As wisdomkeeper says, the fuses are generally marked on the board with F1, F2, etc. Generally, if you look around the area where the DC jack is connected to the board, you may see something like the fuse on the left in this photo:

http://www.kawakami-ca.com/images/t22_main_fuses.jpg

Here F2 is the main fuse protecting the DC input jack. It's a Littelfuse 429007 (7 amps) which has been used in many Thinkpads. I'm not sure if this is the case with your T400. I have T410 and T420 but have not yet stripped the system down to the motherboard. If this fuse tests okay with an ohmmeter, then start looking at the other components on the motherboard for any obvious damage.