I have Toshiba satellite L450, when I press POWER button to start, for the FIRST time the processor fun is run for 30 second .but after that on SCREEN there is no signal. The power light only gives light. So what is the problem is there any one help me?

Tanks
Check first if you can boot to safemode to see if the problem is persistent. Or connect and external monitor to RULE out also the problem. You could also reseat the RAM module/s or if you have 2, try using one alternately on 2 slots. Make sure the fan is also in good working condition as you boot the laptop. Check for any loose, damaged wire/cable. Any previous issue that might have come to this case?What happened leading up to this ? ?

More details...I Disassemble everything all component and check all parts .I didn’t see damage part ,may be is it have  reset jumper on board ? some laptops have reset jumper around ram or processor ,but when I search the same place a couldn’t get the reset jumper .if u know  tell me .

Tanks
1. Quote

Check first if you can boot to safemode

Or connect and external monitor to rule out also the problem

You could also reseat the RAM module/s or if you have 2, try using one alternately on 2 slots.

Make sure the fan is also in good working condition as you boot the laptop