How can I safely downgrade my Sony PSP firmware? - Ask Dave Taylor
DOWNGRADE ALL PSP MODELS FROM 6.60 6.38 6.39 6.35 6.20 TO 5.03 6.20 6.35 6.39 *NO PANDORA* - YouTube
4 Ways to Downgrade a PSP - wikiHow Fun
After having problems getting the system to power on consistently, I finally got it to downgrade back to OFW and now it turns fine. Gonna try a fresh install of infinity tonight