Hi :
I´m looking for a way to know if a HP rack blade is On.
Try some of these oids and see... I'm not positive but I think HP Bladecenter can be monitored through the CPQRACK MIB:
http://www.oidview.com/mibs/232/CPQRACK-MIB.html
Adding the management blade nodes should return all objects in the chassis
Can you see any data if you browse to your chassis XML service?
http://your_chassis_ip/xmldata?item=ALL