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I have a device that has a blown Daito BD20 DC400V 2A fuse. Datasheet here: https://www.furutaka-netsel.co.jp/pdf/daito/bd.pdf . These are rather odd looking, solder-in fuses and they are apparently a bit hard to find. The fuse also has an interesting internal construction; the top just snaps on so I originally thought it was a fuse holder and popped the top off. The fuse element itself appears to be contained inside of a rubbery silicone compound, and the cap contains some padding that surrounds the silicone. Is there anything special about this particular type of fuse that I should look for in a replacement?

Fuse in question

Disassembled

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  • \$\begingroup\$ cut it open and see what's inside .......... is the device used in a high vibration environment? \$\endgroup\$ – jsotola Nov 20 '18 at 0:39
  • \$\begingroup\$ It's in a big rack mount lab power supply, specifically a Keysight N5766A. \$\endgroup\$ – alex.forencich Nov 20 '18 at 0:48
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    \$\begingroup\$ The supply appears to be a rebranded unit from TDK Lambda, so perhaps this is just a relatively generic fuse from a local Japanese supplier. \$\endgroup\$ – alex.forencich Nov 20 '18 at 0:52
  • \$\begingroup\$ get a glass 2A fuse, break it and extract the fusible link inside by heating the endcaps with a soldering iron .... solder the fusible ink into the holder that is pictured above \$\endgroup\$ – jsotola Nov 20 '18 at 21:18
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As with many things, the answer is: Depends.

It's impossible to know what the designer's requirements are when they specced the part, so without asking them, we can make some educated guesses.

Within a certain range of products, the key specs that will matter will be current rating, and "slow blow" or "fast blow". These may or may not be written in the datasheets, but they will be shown as a time/current graph.

https://www.digikey.ca/product-detail/en/littelfuse-inc/80712000440/F4219-ND/3130994

This seems to meet most of your key specs.

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  • \$\begingroup\$ So, after doing some searching around in the digikey parts catalog, the fuse you linked seems to be the best replacement part. There are others with similar ratings, but this seems to be the only one that also has a matching footprint. Anyway, the part has been installed and the device is now working again. Thanks! \$\endgroup\$ – alex.forencich Nov 25 '18 at 22:32

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