faulty power supply inside Toshiba laptop?

Got a Toshiba sp6100 model: ps610e-03skv-en the problem is there some sort of power supply fault with the main board, ive check the power cable adaptor working fine, checked the main laptop battery thats fine i think!! it holds charge when laptop work for a bit, (also laptop will switch on without main battery in and will charge battery as battery light in on and charging when all is off and main power charge is pluged in) laptop will just switch on sometimes and not back on for a while need to unplug power supply connect again and try switching on sometimes will work sometimes not at all, when it does it will start in boot mode and display says BAD RTC BATTERY BAD CHECK SUM (CMOS) CHECK SYSTEM.THEN PRESS F1 KEY , then i press F1 key exit without saving as you cant change any on the battery setting in the cmos!!! computer will start work for a while may be 2min or 10 mins or even 1 hour if am luck and just switch off when working, all help thanks in advance my email address is rs4_boy@hotmail.com once again thank you if you can help me I would like to repair this to board level