RE: How to convert an ATX power supply to rc use
Thanks for the pics. Couple points I want to mention though:
1) The two heatsinks doesn't necessarily mean two rails. Actually usually one heatsink is for the AC mains side switching section (FETs, bridge rectifier, etc), the other heatsink (closer to the output wires) is for the output FETs and associated components.
2) To really see how many 12v rails there are, you'd have to pull out the PCB and follow the traces. Even though there are 3 sections, they could simply be tied together via copper traces underneath. However, there are three coils/caps per output wire, but that could just be paralleled/split to help handle the high currents without using larger (and more expensive) components. Again, a peek at the traces (especially before the coils) would tell you more.
3) All the grounds are the same point. Typically, I use the same amount of grounds as the yellow wires. So, if I bundle 6 yellows together, I'd also bundle 6 blacks together. Since all grounds go to the same point, it doesn't matter which ones you use - there are no separate 5v, 3.3v, and 12v grounds.
It is odd that the PCB has three 12v outputs labeled, but specifies only two on the outer case label.
I probably should go look at the ATX spec, but I assume the red/brown connection consists of the 5v line and the 5v sense wire tied together?