First post, by songoffall
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So here's a word of advise for beginners - I'm pretty sure the veterans already know this.
I made a few of quite silly mistakes - and the sad part is, it was not for lack of knowledge, but more because of assuming things.
1. After quite a bit of system instability, my system stopped working. I checked the power supply - bridged 18 to 19, the fan would start to spin, then stop, with no readings on rails. I replaced the PSU and my system wouldn't post - both the power and HDD leds were on, but there was no picture and the system was stuck.
While this usually means that the motherboard or some device connected to it is malfunctioning - like a connection to ground that lowers the voltage on one of the rails - I tried to disconnect everything, even assuming that the motherboard was dead - which would be terrible, because it's a very nice nForce 2 socket A motherboard - turns out I had two bad PSUs with two different issues.
This PSU's filter caps had brown flaky residue around them - bulging isn't the only way these electrolytic caps die, they might also just squirt their electrolyte from the bottom. Replacing them fixed the issue. I also removed a bunch of wires I didn't need, like the 4 pin CPU power connector and the 4 detachable pins of the 24 pin ATX 2.0 connector, effectively converting the PSU to an ATX 1.0.
2. So why did the original PSU fail? Because I assumed that an old 500W PSU could power an old Athlon XP 2000+ CPU.
Thing is - Athlon XP CPUs need quite a bit of current on the 5v rail. The PSU I was using had the following current ratings:
+3.3V - 22A
+5V - 16A
+12V - 15A+16A
-12V - 0.8A
+5VSB - 2.5A
These ratings on an old off-brand PSU should be taken with a grain of salt, and I wouldn't expect it to actually work fine with more than 10A on the +5V rail.
Visually examining the failed PSU, the PCB has darkened in certain spots, especially under one of the transformers, so I don't expect it to be repairable, but I salvaged its filter caps and will put it in storage as a donor.
Now the PSU I'm using isn't great either. While it has 28A on the +5V rail, which is enough for Socket A (anything at or above 25A should be fine), +3.3V rail only has 12A. But as the Athlon XP CPU is using the +5V rail for power, I should be fine.
3. If you see transparent plastic capacitors in your PSU, usually branded RIFA, especially if they are cracking, you might want to replace them. Unless you're a fan of the smell. These are power filter caps, and back in the day people didn't realize they didn't perform well in AC circuits and would often fail. And their failure mode was exploding, releasing magic smoke and a wonderful scent that will stay with you for days.
4. Back in the day we would often remove the grilles on old PSUs, because old grilles were crap, created turbulence on exhaust and caused a lot of noise. You should put an aftermarket wire grille on the fan though, because you don't want stuff to go inside your PSU fan, like a stray cable. I also soldered the 3-pin header from a 3-pin fan to MOLEX adapter to the PSU PCB to be able to use modern fans with it - a Noctua 80mm fan, in this case.
Something that makes me more optimistic about this PSU: it runs a lot cooler, the old one exhausted noticeably warm air, while this one is just room temperature. The heatsinks on this one are far worse though. But it is what it is, I guess.
Compaq Deskpro 2000/P2 300MHz/384Mb SDRAM/ESS ES1868F/Aureal Vortex 2
Asus A7N8X-VM400/AMD Athlon XP 2ooo+/512Mb DDR DRAM/GeForce 4 MX440/Creative Audigy 2
Asus P5Q Pro/Core2 Quad Q9400/2Gb DDR2/GeForce 8800GT/Creative X-Fi