They just connect straight to the PC via USB and draw power from that do they not?
Are you sure you're not confusing it with the U360?
There's nothing about USB on happ's site.
I have P360's in my current cabinet w/ jamma sfIII:3s. No USB. Here's what the wiki has to say about the additional +5v wiring:
http://wiki.arcadecontrols.com/wiki/Joysticks#Happ_Perfect_360_.28P360.29Happ Perfect 360 (P360)
The Perfect 360 joystick is an optical joystick, which means that the position of the handle is read by optical switches, instead of conventional leaf switches or microswitches. This gives near-silent operation, as the handle & actuator never touch anything.
These sticks have a very smooth feel, largely due to the "no touch" action. P360 joysticks have a round restrictor, instead of the more common square restriction found on many other modern joysticks. This round restriction adds to the smoothness factor, because there are no corners to feel.
Connection- P360 joys require a little more effort to hook up- in addition to the Up, Down, Left, Right and Ground connections on standard joysticks, the P360 also needs a +5 volts connection. This is easy enough to get, as encoders such as the I-Pac and KeyWiz provide a +5v header. PC power supplies produce +5v on the red wire of the drive connectors. There is also +5v power available on USB & PS2 cables. +5 volt power is easy to find.History- The Perfect 360 started out as an aftermarket add-on kit for Wico leafswitch joysticks. Models were later added to the product line to convert Happ Super, Competition, and Ultimate sticks, and possibly others as well. Happ eventually bought the rights to the P360 technology, and discontinued the kits. Happ began producing a complete stick instead, with the top half of a Wico joystick base (no longer sold by Wico by then) mated to a P360 bottom half.
Interchangability- P360 handles and Wico handles have been found to be interchangable. There are also replacement handles available from SlikStik. Wico Pear-top sticks used the same pivot cones and spacer sleeves.