How to fix black screen on psp

guys, help me pls, is there any step to fix this problem. when im install the CFW 5.50 Gen-D and after the installation hve done, i try to turn on my psp but there is no picture on the screen, just a green light. please. i knw this is because the CFW. but someone please help me, i really need your help. i've search so many website to fix this but its not working. they say i hve to use pandora batt, and where should i buy this stuff? is there any other way?

thank you

 

guyss, pls tell me how

 

thanks, but i've already sent my psp to the shop to repair it, but idkyet they can fix it or not. if not i've to use the pandora batt isn't? btw thanks again.

 

im using psp-2001.