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The fuse on one of my commercial printers blew. See picture below. I am planning on replacing it but cannot find an exact fit. The closest I can find is another 400mA / 72v fuse that is labelled as "radial" instead of being the usual ones found in a main board.

This fuse leads directly to the printer's piezoelectric printhead, so it's important. It's a very expensive part to replace (around 1,800 USD for the part + labor).

Here's a link to the closest fuse I can find in terms of mA and voltage: https://www.digikey.com/en/products/detail/bourns-inc/MF-RX040-72-0/2045641

And here's an apples to apples (in terms of looks) fuse I found that doesn't match the requirements exactly. Its indeed 400mA but only at 50 volts DC. https://www.digikey.com/en/products/detail/SF-0603F040-2/SF-0603F040-2CT-ND/8747908?itemSeq=354051583

I'm a beginner at this and I really appreciate any help offered.

Alex

enter image description here

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    \$\begingroup\$ You need to be very careful replacing that fuse if it's part of expensive equipment. There are properties other than voltage and current rating that you must match as well. Have you found a correct datasheet for the recommended part? The other thing is it's a good idea to determine why the fuse blew. Have you? If it was due to damage or deterioration of other parts in the circuit, the replacement will blow too, even assuming you spend the $1800. If that quote isn't from the manufacturer, it would be a good idea to contact them. \$\endgroup\$
    – K H
    Feb 12, 2021 at 1:53
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    \$\begingroup\$ The datasheet of the "matching" fuse you found lists its breaking capacity as 50V, 50A, meaning the circuit may not break adequately if those values are exceeded. There are no graphs or derating factors to indicate performance above those ratings, so you'd be giving up ability to claim due diligence. The through hole fuse you've linked is resettable. It has slightly different resistance, and 8x as much resistance an hour after tripping and "resetting itself". Could cause damage from repeated tripping/"brownout". \$\endgroup\$
    – K H
    Feb 12, 2021 at 2:06
  • \$\begingroup\$ Already contacted manufacturer. They don't want you to fix the motherboard but rather buy a new one. \$\endgroup\$
    – Alex
    Feb 17, 2021 at 20:00
  • \$\begingroup\$ In that case it is quite possible the manufacturer used custom fuses, and or other custom components to prevent user or third party repair. When this happens the only user repair option is to purchase multiple broken devices and use them for spare parts. Electronics components age somewhat predictably, so if they're providing a 3 year warranty for example, MTBF(Mean Time Before Failure) can be aimed at roughly 4 years, resulting at few failures during the warranty period and a lucrative repair/maintenance market. \$\endgroup\$
    – K H
    Feb 18, 2021 at 2:17
  • \$\begingroup\$ Add in "irreplaceable" custom parts (there's nothing special about that fuse other than that you'd need to mass order to get your own batch of custom replacements) and you have a protected market as well. Aside from that, the engineers can save a bit of design time by ordering the part with the specs they need rather than designing the circuit to work with common parts. You hear more about it with proprietary ink and cartridges, but the printer market in general is full of protectionism. \$\endgroup\$
    – K H
    Feb 18, 2021 at 2:21

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It's quite dangerous to rematch a fuse… current curve should be exactly the same, and of course the other parameters should be at least the same (working voltage and interruption rating).

Also, the real problem is: why did that fuse blow? Most probably there's something wrong in the board.

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Update: The original fuse blew for unknown reasons. I think I might have shorted the circuit when replacing the printhead. It blew not during normal operation of the printer, but when untrained hands started performing service repairs.

At this point the motherboard no longer works due to the blown fuse, so I don't mind tinkering with it and trying to fix it. The likelihood of causing more damage is low and worth the risk.

Thanks everyone for your answers. I will update when its all fixed.

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