Laptops

This answer may sound terse and rude.

Basically, if you have the skills to trouble shoot a motherboard, you would not need to ask this question.

For a well trained electronics technician, most of the trouble shooting and debug tasks on even a dead motherboard are very straightforward. You check the power supply, clock and reset circuits.

Repair work on the other hand requires some specialized and expensive tools. To remove and replace most of the components you need some very specialized desoldering and soldering equipment. Even for just a simple bad capacitor or voltage regulator you need the correct tools and skills or you will damage the board when you remove the part.

One reason that there is so little component level repair performed on computer boards is that the cost for a skilled technician and rework operator can quickly exceed the cost to build a new board.

Chas