This sucker is also the destroyer of worlds if you anger it.
The PS1 fuse is there for the power and eject buttons. If you've never opened a PS2, these are a nightmare. They're attached by a ~8 inch ribbon cable to the motherboard. The actual power and eject buttons are connected to the top of the case, meaning you have to walk on eggshells every time you open the PS2.
This fuse blows at the slightest disturbance. I blew mine out just doing some routine maintenance. I found that I had a V4 PS2 and not a V3 as I thought, so I bought a KHS-400C laser since they're reputed to be more reliable (it does seem to be). Anyways, while I was closing up the system I didn't have this ribbon cable seated well. It was slightly off, which shorted the cable and blew the PS1 fuse.
Shitty. Without the PS1 fuse functioning, there is no way to turn on the PS2 and use it. I don't like how easily this fuse blows, so I wanted to negate any future issues. I considered bridging the fuse, but if it blows that easily, this seemed like a bad idea. Enter resettable fuses. They don't blow like traditional fuses, and they're widely used in modern electronics. Opening any recent game console, you'll see resettable fuses everywhere. As always, Wikipedia has the rundown.
The PS1 fuse for a V4 PlayStation 2 is a 400 miliamp (or .4 amps) fuse rated at 12 volts. I couldn't find a 400mA 12v resettable fuse, so I bought a 400mA 60v fuse. The voltage really doesn't matter here, the amps do.
There's not enough clearance on the board for the resettable fuse to stand, so I trimmed the legs quite a bit and laid it down. Since the fuse is blown, you don't need to remove it; the current isn't moving through the fuse, so soldering either end of the fuse to the other will bypass the blown fuse. I left the original PS1 fuse in and soldered the resettable fuse to the sides of the fuse. This made life considerably easier since the original fuses are surface mount components.
There it is all installed. I trimmed the legs down to where they bend inwards. It was the perfect size to fit right against the edges of the original fuse. I had concerns about this working even though it was completely sound in theory. I reassembled everything and...
Now I can get back to Final Fantasy XII. I did have a working PS2 slim, but I really hate that thing. Plus I'm very attached to my HDD mod now. I'll do a post on setting all of that up soon.