In a computer of a friend, an EAGLE 400W power supply was used.
Claims:
- Maximum continuous output 400W
- 12V: up to 17A
- 5V: up to 40A
- 3.3V: up to 28A
- Total on positive rails 380W
- Total on negative rails 11.1W
- Total on standby 10W
- 401.1W (400W max)
Okay, so the numbers add up but can it actually manage 400W?
No way. Said friend was using it in a gaming rig, where a minimum 350W is advised by the graphics card manufacturer. They reported their games would often freeze and the computer often rebooted itself. So he tried everything, reinstalled the OS, changed the hard disk, even replaced the RAM, and it still gave problems. Then, one day he was showing me a game, it froze (like normal) and then suddenly BOOOOM the power supply exploded in a shower of sparks and smoke and the computer turned off. It scared the @#*! out of me! The computer was okay after a new PSU was fitted, thankfully.
So he gives this piece of now fried PSU to me and I find that this power supply was just waiting to fail. On the main board of the power supply it says (for the fuse): 5A for 180W-235W, 6.3A 250W-350W. A 5A fuse was fitted. So this PSU would barely manage 235W, let alone 400W. Luckily the fuse did its job, it blew. (Plug fuse did *not* go.)
What actually went wrong? It seems to be a case of catastrophic failure. I know what caused the complete failure of the PSU. It was the power MOSFETs going pop. They basically became 20 ohm shorts (as tested with my multimeter.) Dumping ~400V from charged caps into 20 ohms is bound to incinerate anything. Both of them simultaneously went bang (or possibly the failure of the first caused the failure of the second) and this is probably what caused the sparks and explosion. But the MOSFETs were not alone in the parts that failed. Several resistors and a capacitor were also popped, but these were all on the secondary side, well away from the fireball from the MOSFETs which charred other parts. It seems to me like something in the feedback loop went crazy and caused the transistors to pop whilst also causing damage to the secondary side components. Also, the output filter caps are bulging; possibly the reason it was often crashing the computer.
It's very much apparent that this power supply ran hot, because the PCB is discoloured in many places around high power components. Also, the Schottky diodes on the output are underrated. 40A for the 5V (just in spec), 20A for the 3.3V (out of spec, requires a minimum of 28A), and 16A for the 12V rail (which is rated to 17A.) And being "5V heavy" (more current on the 5V rail than 12V) means modern graphics cards won't work too well on it...
So does anyone know what would cause this? Seems that these cheap power supplies are very dangerous. This could have easily started a fire.
Tom
Claims:
- Maximum continuous output 400W
- 12V: up to 17A
- 5V: up to 40A
- 3.3V: up to 28A
- Total on positive rails 380W
- Total on negative rails 11.1W
- Total on standby 10W
- 401.1W (400W max)
Okay, so the numbers add up but can it actually manage 400W?
No way. Said friend was using it in a gaming rig, where a minimum 350W is advised by the graphics card manufacturer. They reported their games would often freeze and the computer often rebooted itself. So he tried everything, reinstalled the OS, changed the hard disk, even replaced the RAM, and it still gave problems. Then, one day he was showing me a game, it froze (like normal) and then suddenly BOOOOM the power supply exploded in a shower of sparks and smoke and the computer turned off. It scared the @#*! out of me! The computer was okay after a new PSU was fitted, thankfully.
So he gives this piece of now fried PSU to me and I find that this power supply was just waiting to fail. On the main board of the power supply it says (for the fuse): 5A for 180W-235W, 6.3A 250W-350W. A 5A fuse was fitted. So this PSU would barely manage 235W, let alone 400W. Luckily the fuse did its job, it blew. (Plug fuse did *not* go.)
What actually went wrong? It seems to be a case of catastrophic failure. I know what caused the complete failure of the PSU. It was the power MOSFETs going pop. They basically became 20 ohm shorts (as tested with my multimeter.) Dumping ~400V from charged caps into 20 ohms is bound to incinerate anything. Both of them simultaneously went bang (or possibly the failure of the first caused the failure of the second) and this is probably what caused the sparks and explosion. But the MOSFETs were not alone in the parts that failed. Several resistors and a capacitor were also popped, but these were all on the secondary side, well away from the fireball from the MOSFETs which charred other parts. It seems to me like something in the feedback loop went crazy and caused the transistors to pop whilst also causing damage to the secondary side components. Also, the output filter caps are bulging; possibly the reason it was often crashing the computer.
It's very much apparent that this power supply ran hot, because the PCB is discoloured in many places around high power components. Also, the Schottky diodes on the output are underrated. 40A for the 5V (just in spec), 20A for the 3.3V (out of spec, requires a minimum of 28A), and 16A for the 12V rail (which is rated to 17A.) And being "5V heavy" (more current on the 5V rail than 12V) means modern graphics cards won't work too well on it...
So does anyone know what would cause this? Seems that these cheap power supplies are very dangerous. This could have easily started a fire.
Tom
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