fuses-fast acting vs slow blow

[Jolly Roger]

My amp blew a fuse and I cant seem to find a slow blow fuse for it. A fast acting one will work right? and how do they differ? Thanks JR

[JohnA]

A fast acting fuse will be fine for a temporary cure. A fast acting fuse blows the second its current rating is reached. A slow acting fuse can tolerate rated curent for a few seconds to get you past a musical peak before it blows.

John

[HDBRbuilder]

It used to be that you could find just about any fuse, fast or slow blow at the discount stores, but, alas, that is now seldom the case...BUT you can try most automotive stores and get your fuse there...just be sure to have to the old one with you or its full alpha/numeric and brand nomenclature so they can get the correct one for you.

I would suggest getting a few of them and taping a spare in some inconspicuous place on the piece of equipment to keep it handy.

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[Malcolm]

Like John says, it is safe to use a fast acting fuse in place of a slow blow. It just might fail where the slow blow would survive when you get close to its limits. Replacing a fast acting fuse with a slow blow usually isn't a good idea, however.

A fast acting fuse doesn't actually blow as soons as its current rating is reached. If you were to look at the ratings of a garden variety fast acting fuse, you might see ratings of a few hours at 100% current, a few seconds at 200% current, and a curve in between. Slow blow fuses just give you a little extra leeway over fast acting fuses to handle starting current, like charging power supply capacitors.