... -on your power supply ;Plug-in your 24 pin power supply connector to mini tester;Check LED light if ON or OFF (+5V, +12V,+3.3V ... ,-5V,-12V,+5VBS,PG);Plug ... (SB) 12V, power Good (PG)Connectors: Floppy, HDD, CDROM, SATA, 4 pin(p4),8 pin(Dual-CPU). 6 pin (PCI-Express) LED power supply tester