I have a toshiba satellite a305-s6909 and just replaced the motherboard and when i went to power it on nothing comes up on the display the screen stays black?????

most likely it is the power supply section has a fault.
Most common fault is the capacitors.

Check if d flex if broken or d ram is bad

My Toshiba A305-S6872 laptop is OVER HEAT UPTO 45degree centigrade so what can i do the fan is working.

Assuming there's a good input from the battery or the charger. If there's no activity,bios screen or boot screen. Then you motherboard has probably failed.

Problem description: The laptop shuts off when AC power adapter is plugged in. The laptop works fine on battery power but as soon as you connect it to AC adapter, the laptop turns off.
Possible cause: 1. Power adapter failure.
2. Motherboard failure.
Possible troubleshooting steps and repair solution: First of all, test the power adapter. Make sure the adapter outputs correct voltage. It's possible that the output voltage is not correct and the laptop shuts down to prevent the damage. Test your laptop with another known good power adapter.
Toshiba Satellite A305 AC Adapter
If the problem still exists, even after replacing the adapter, most likely it's the motherboard failure. Replace the motherboard.

This sounds like a display issue. Have you tried hooking the laptop up to an external monitor?

Hi,
you probably have a loss connection between the motherboard and screen or try to update your video driver.

Have you tried running it without the battery?

• If this works, then the battery has died. Replace it or run on p/s alone.
  
• If not, and the power supply is definitely working, then the laptop itself needs repair.

so it is your display resolution issue.
When you power up press continue F8 key then enter in enable vga mode.
Then go to control panel and dispaly proeprty then change screen resolution to 1024*768.

but if you not see safe mode and other menu then you have to check your ram and motherbord.
Also check your Lcd screen.
Let me know if you need more assistanse.
Thanks.

i think the driver is not properly installed so you may try to install the driver by finding the appropriate driver for your sd card and you can find it in toshiba site