Hi there, I have a toshiba A75 laptop that does not boot when on ac power without a battery beyond bios. It shows the splash screen but then dies on normal boot.

When I have the battery in and the unit is powered off It does charge the battery.
When the battery is fully charged, it will run and boot into windows but does not recognize the ac power at all. It just drains the battery, then when the battery is at 0 it shuts off and this is while connected to AC power and the LED see's the AC power.

When on AC power I can boot into bios and it will sit there for days without a battery, but when I try to get to the OS it just shuts down. I have replaced the mobo twice. I have replaced the hard drive as well. The odd part is that with the hard drive out of the laptop, I can get the laptop to run with out any power failures. It just recycles the media device failure message but does not crash.

I have tested the power supply on other laptops and it seems to work just fine.

Any one have any ideas?

Since you have replaced the system board twice, this probably does not apply to you... but we have seen a number of Toshibas with the same or similar motherboard where the power jack on the board became loose or disconnected. A new jack had to be obtained and soldered back into position.
If you bought used boards or refurbished boards, this difficult jack problem could have been the cause. It requires a special cold solder technique and is awkward to access, but when done properly by an experienced tech, it can save a laptop.
There are several Dell Inspirons and Sony laptops with the similar problem.
We have seen costs in a shop as high as $160 for this repair... but the part is only $6.00 so I don't know how they justify the high cost.

I did the repair and I had the same issue, so I replaced the board and now I am on the second one. What confuses me is that if I stay in bios the laptop stays up on ac power, but the laptop powers off when I try to go into windows right after the splash screen. If I remove the hard drive, it seems to be ok. I am at a loss as to what could be the culprit.

Gazdag6

I have the same problem with a Toshiba A75-S209, it goes to battery mode as soon as it enters windows but it would stay forever in the Bios and the only way to use the laptop is to charge the battery when the laptop is off and use until the battery discharges, checked the power jack and it seems to be fine, upgrade bios to lattest version (1.6) and still the same, it seems to be a problem related to a defective part in the mother board, will keep investigating, this is really strange, have you found anything since your last post?

Thanks:
Saul.