My laptop toshiba a105-4004, no power on, but 3.3vpresend at power switch and 3.3vpresend on kbc1122 sio chip but no power on,power switch and cable also ok,is it possible to chenge sio chip? please t

No light on screen at all, but Power ON LED lites?
Try different memory chips. Screen won't liteup with a bad memory chip.

If its not powering on 3 problems could be there the battery/ the power supply or the power management chip or lastly the charge chip around the inside of the laptop inside its self

If you've replaced the battery, AND power cable (I assume you replaced the entire AC Adaptor), then most likely the power board needs to be replaced in the laptop. Most of the time, this is fixed to the motherboad, therefore the motherboard would need to be replaced.
I suggest you having someone who has the experience doing this do it, or take it to a repair shop.... or chuck it and buy a new one =).

Hi,
Does the display show anything before you enter windows? If yes, then press the key to transfer video back to your original screen once you enter windows. It should be the function key "Fn" + F5 - F8. looks for the icon which shows a monitor or says "CRT/LCD".
If it doesn't show anything before you enter windows I'm afraid your screen needs to be replaced. Good luck.

You're describing a well known problem with Toshiba laptops, especially the M30 and A70 series. This is the Maxim 1987 power chip issue, here's an illustrated repair manual for your laptop's motherboard. Basically, you'll need to resolder the Maxim power regulator chip, which is not a very difficult thing to do, and the good thing is that you don't need to buy any new components, or reinstall anything. The repair process takes about an hour (if you have the tools).

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sounds like a Maxim power driver failure. You'll need to do a redistributive resolder. Check out this tutorial for Toshiba m35 laptop main board repair of the Maxim 1987 power chip. This is a fairly common problem with plenty of Toshiba and HP laptop models, and experience the same symptoms that you list. Hope this helps.

If you're lucky, you may only resolder the power plug onto the motherboard and that's it. This is a known problem with this and many other laptop models, like the Toshiba m35. Unfortunately, NC6xxx series suffer from yet another power-related issue: the Maxim chip problem, and the solution is performing a redistributive resolder. For more info take a look at this post for power plug and Maxim 1987/ Max1532 chip resolder instructions http://ebooksandtutorials.com/toshiba-m35-hp-nc6000-laptop-repair-manual

okie thank me a lot first cos i have the solution or atleast the reason... hate me cos i am the bearer of possibly bad news... the problem is at chip level... a processor needs to be supplied with uniform voltage and power for uninterrupted operation whil handling huge calculations it is not capable of withstanding sudden changes in voltages... for this purpose what we have on a mobo is a chip called the core voltage controller this chip makes sure that the voltage sent is uniform... this chip on ur system is blown
2 solutions exists take a deep breathe relax one is to replace the mobo-cost approx400$ take a deeper breathe ask for toshiba assistance instore and get this chip replaced cost 100$(i took the second option costed me 4500 rupees in India)

Sounds like there is a faulty connection between the power switch and the computer. Probably why its making a little noise.
Take in for repair and replace power button.

I've seen this many times. A chip on the mother board didn't get the proper amount of solder during manufacturing. Now when the system heats to a certain point the chip legs actually pop up off the mother board thus stopping the PC. I've repaired these before using a microscope and a tiny heat source.

Good Luck