What could be wrong? Is it bad power jack or the motherboard is dead?

By the way, the power jack aka DC-IN jack is the power socket on the side or back of your laptop where you plug the AC/DC power adapter.

I’ll explain how to perform basic troubleshooting and find out what is wrong. This is only for experienced people, who know how to disassemble laptops.

First of all, test the AC/DC power adapter with a multimeter. It’s very likely that there is noting wrong with the laptop and your problem is related to the power adapter.

If the adapter tests fine and output correct voltage, disassemble the laptop and remove the top cover.

As you see on the first picture, in my laptop the power adapter plugs into the DC-IN power jack which is connected to the motherboard via a harness.
In some models the DC-IN power jack is soldered directly to the motherboard.

Plug in the power adapter and measure voltage at the point where the DC-IN jack or DC harness (like in my case) connected to the motherboard.

If you are reading the same voltage as on the AC adapter, it means the power jack or harness works properly and the problem is related to the motherboard.

If there is no voltage, most likely there is a problem with the jack or hardness and it has to be replaced.

By the way, in some case the problem could be related to the fuse which is usually located somewhere very close to the power jack/harness connector. You can test the fuse with a multimeter.

If the fuse is bad, the motherboard will appear to be dead even if there is nothing wrong with the power jack and AC/DC adapter. If that’s the case, replacing the bad fuse should fix the problem.

If your Toshiba Satellite M35X laptop is dead (out of warranty) and you would like to fix it yourself, you should take a look at this post. Apparently there could be a problem with the MAXIM chip witch is located on the motherboard, on the right side from the video cable connector.

Official service centers will list buying a new motherboard as the only solution for this problem. However, a new motherboard is not the only solution. Fixing the old motherboard is a better, faster and incomparably cheaper option. The entire process of opening up, repairing and reassembly of the laptop will not take about an hour.

This guide is only for experienced technicians. You have to be able to disassemble the laptop, remove the motherboard and resolder the problematic chip.

Also, Toshiba Satellite M35X is know for the following problems:
1. Overheating – when the cooling module gets clogged with dust.
2. Power jack failure. In this case you’ll have to remove the motherboard and resolder the power jack.

When I try to turn on my notebook the key board lights up, it starts to boot then stops, shuts down and repeats the cycle. The screen does not come up during all of this. The cycle is about tree to four seconds long. It has been suggested that the power supply might be bad. What do you think? Also I am having some trouble getting this thing apart to inspect for loose connections. How do I open this sucker up ? Thank you for any help you can give me! This is a HP Pavilion ze 4400 notebook.

Does this happen if you start the laptop on the battery power, without power supply plugged in? If yes, then most likely it’s not the power supply problem.
First of all I would check the memory. Try reseating the memory module, make sure the contacts on the module are clean. Try moving it from one slot to another. If reseating will not help, find a known good memory stick and test the laptop again. Try starting the laptop without the hard drive. Sometimes a failed hard drive can halt entire system.
Finally, minimize the laptop as much as you can. Check all connections. Remove all devices and leave only three main parts: motherboard, processor and memory. Test the laptop with an external monitor. If you still experience the same problem most likely you have a failed motherboard.
The maintenance and service guide for HP Pavilion ze4400 has step by step disassembly instructions. Take it apart at your own risk.