Toshiba satellite a205 will not turn on is it the power supply regulator on top rear panel?

charge battery and test with no AC adapter power.If it boots OK a chip that regulates power is faulty on the motherboard

check ram and power button

use old battery first try to boot
if your system is boot run bios update from intel.com
then change new battery
else run bios flash from chip level service provider

http://www.irisvista.com/tech/laptops/toshiba-satellite-a205/laptop-disassembly-1.htm

1) ALL power removed. Remove the AC adapter (Charger), and Battery.

2) Turn the laptop over bottom side up, Battery Compartment facing AWAY from you, down on a table.
You may wish to lay a soft Static free cloth on the table, to prevent scratching the table, or laptop.

3) Take this cover off,

http://www.irisvista.com/tech/laptops/toshiba-satellite-a205/big/toshiba-satellite-a200-a205-02.jpg

Remove the Ram Memory module/s. ('Stick')
Lay them/it carefully aside. Handle by the BODY. The Body is everywhere on the Ram Memory module, EXCEPT the gold plated contact pins at the bottom.

The Body is coated with a see-through protective plastic.

4) Remove this Philips head screw, and push the optical drive out,

http://www.irisvista.com/tech/laptops/toshiba-satellite-a205/big/toshiba-satellite-a200-a205-03.jpg

The top of the optical drive will have small Philips head screws, or Torx screws. They sell Torx screwdrivers real cheap,

http://en.wikipedia.org/wiki/Torx

Remove the screws, remove the cover, remove the disk.

Regards,
joecoolvette

[Sounds like you may need a replacement optical drive ]

If it does the same thing w/ the battery removed and just on AC, it's a power regulator problem on the motherboard. If it works with the battery out, the battery is dead and you need a new one.

- possible problem with the AC power supply
- try using a different AC adapter. if issue persist try flashing the BIOS. if issue still persist then have the motherboard checked out.

there may be a problem with ur power adaptor or ur battery charging section

clear the bios by removing the small battery on the mainboard for 10 hours.the power on

here is the link :
http://www.csd.toshiba.com/cgi-bin/tais/support/jsp/modelContent.jsp?ct=SB&os=&category=&moid=2211892&rpn=PSMC4U&modelFilter=M205-SP3018&selCategory=3&selFamily=1073768667&selModel=2211892|PSMC4U

Satellite A200-ST2041, A200-ST2043, A200-ST2042, A205-S4617, A205-S4618, A205-S4639, A205-S4638, A205-S4537, A205-S4557, A205-S5816, A205-S5814, A205-S5813, A205-S5812, A205-S5811, A205-S5810, A205-S5809, A205-S5806, A205-S5805, A205-S5851, A205-S5847, A205-S5843, A205-S5841, A205-S5835, A205-S5831, A205-S5825, A205-S6810, A205-S5823, A205-S5804, A205-S5803, A205-S5801, A205-S5800, A205-S7468, A205-S7466, A205-S7464, A205-S7459, A205-S7458, A205-S7456, A205-S7443, A205-S7442, A205-S4797, A205-S4787, A205-S4777, A205-S4707, A205-S5863, A205-S5859, A205-S5855, A205-S5853, A205-S5852, A205-S6812, A205-S6808, A205-S5821, A205-S5819, A205-SP5822, A205-SP5821, A205-SP5820, A205-SP5818, A205-SP5817, A205-SP5816, A205-S5000, A205-S5866, A205-S5879, A205-S5878, A205-S5872, A205-S5871, A205-S5867, A205-S5880, A205-S5861, A205-S5833, A205-S5864, A205-S4629, A205-S4607, A205-S4597, A205-S4578, A205-S4587, A205-S4577, A205-S4567, A215-S4697, A215-SP5811, A215-SP5810, A215-S48171, A215-S4817, A215-S4807, A215-S4767, A215-S4757, A215-S4747, A215-S4717, A215-S4737, A215-S5839, A215-S5848, A215-S5837, A215-S5829, A215-S5828, A215-S5827, A215-S6820, A215-S6816, A215-S7472, M110-ST1161, M115-S3094, M115-S3104, M115-S3154, M115-S3144, M200-ST2001, M200-ST2002, M205-S3207, M205-S4804, M205-S4805, M205-S4806, M205-S7453, M205-S3217,

Check your power settings. You might have it set to shut off after a certain time of non-use.