My ATX power supply stopped working. After opening it up and probing around (caps discharged), I discovered the 10A/250V fuse (white tube with leads) had blown. I have a ton of the common glass tube fuses, but the 10A ones I have will be a difficult to fit. They're all 6x30 instead of the 5x20 size of the blown one. The rest of the fuses are 240V/5A or lower.

The closest value I have at that size is 12A/250V, but it seems a bit sketchy at a 20% higher rating. In general what's the safety margin for switched mode power supplies?

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    \$\begingroup\$ You realize that a properly designed and operating ATX power supply will NEVER blow its fuse, no matter what you do with the outputs. The fact that the fuse blew probably means that something else blew/shorted which caused the fuse to blow. I expect that if you replace the fuse, the new one will just blow too. \$\endgroup\$
    – DoxyLover
    Jun 28, 2023 at 5:48
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    \$\begingroup\$ Fuse replacement is not a thing you should focus on at the moment. As DoxyLover stated in their comment, even if you replace the fuse it's going to blow up eventually. There must be something wrong with the circuit you have, so consider servicing. \$\endgroup\$ Jun 28, 2023 at 9:59
  • \$\begingroup\$ Yeah, that definitely crossed my mind. I was planning on conducting a thorough test and check all the usual suspects. \$\endgroup\$
    – user148298
    Jun 28, 2023 at 19:08

1 Answer 1


The official default answer is always that you must replace the fuse with (exactly) the same type and rating to provide equivalent protection.

The white (not transparent glass) is a ceramic type and should be replaced by the same type. Fuses are typically marked with type as well as current rating on the end caps.

That said, I agree with the comment that it is unlikely that replacing the fuse alone will result in anything better than another blown fuse, and if you replace it with something significantly worse such as a higher rated fuse of inferior performance you may even cause additional damage.


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