I ran few tests on the modified ATX PSU and I found reliability issue. I’m planning to modify another ATX PSU soon. This time I’ll follow the modification procedure on Reprap Wiki.
10W 10 ohm resistor resulted 11.58V @ 1.17A.
55W 12V headlight bulb resulted 10.09V @ 3.75A.
Connecting two 55W 12V headlight bulbs in parallel made freeze the PSU. I expected to read around 10V but when the power switch was on, it simply stalled. The fan gave a jerk then stopped spinning.
According to Reprap Wiki, RAMPS 1.4 controller requires maxium 12V at 16A. I converted a used 450W ATX power supply for RAMPS 1.4 controller that I bought few months ago for 12,000 KRW.
I installed a power switch and one fuse holder that takes automotive blade fuse.
I merged all positive 12V wires to make two 12V wires whose size is AWG 16 and did the same thing on ground wires.
Installing the fuse holder and power switch
Testing the modified 12V power supply.
Checking voltage of the two 12V wires. Initial test went fine. I was afraid to measure the current using my multimeter whose maximum current is 20A. I’m uncertain how much current this power supply produces without load because I merged the two positive 12V rails – one produces 14A, the other produces 16A. I’ll connect a 12V device that consumes few amperes.