In this case the fuse is sensitive to curent-flow, and not actual Watts, as your calculations (which are correct, just mis-applied) would suggest.

So you should be fine with a 250V unit rated for the nameplate current.

Fuses are based on current, not power (voltage times current); you need to use the recommended current rated fuse :). Put in a 2A fuse, and things should be fine. Since the fuse does have some resistance, and power relates to heat generated, I suspect that higher voltage rated fuses have less resistance than lower voltage rated fuses so less heat would be generated. If so, then the higher voltage rated fuse would be safe to use on lower voltages, but not the other way around. Anyone have any comments on this? Chad Fernandez wrote: > Hi all, > > I went to Radio Shack last night to buy a fuse for my laserdisc player. > I needed a 125v 2amp fuse. Most of the fuses I saw were rated at > 250v. I bought a 250v .75amp fuse, thinking that if I up the voltage I > have to lower the amperage. The new fuse blows instantly. Am I > thinking about this incorrectly? Now, I'm thinking I was wrong since > the fuse still only has 110 voots running through it..... so do I still > need a 2 amp fuse even if it's rated for 250 volts? Can I use a 250volt > 2 amp fuse safely? > > I mentioned that the .75 amp 250volt fuse blows instantly..... does this > indicate that another problem exists, or would the laserdisc player pull > more than .75 amps? The player has been sitting in my living room, > hooked up, but unused for months. I have had electrical storms here of > course, but all my equipment is on a surge protector, and nothing else > has gone bad.... (amps, dvd player, tv). > > Chad Fernandez > Michigan, USA

As I recall from the UL presentation I once attended, fuse voltage is pretty much irrelevant, within certain windows. Most of the reason fuses have voltages ratings has to do with the carriers and the arc-over voltage.

The current rating of a fuse is the current it will blow at. A 2A fuse will blow when more than 2A passes through it, irrespective of whether the voltage supplied to that circuit is 110V, 240V, or 12V. And the current flowing in a circuit does not depend on the maximum voltage a fuse will stand.

Yes, you need a 2A fuse. A 2A 250V fuse would be fine. Also, do you need a Quick-blow ('fast') or anti-surge ('slow blow') fuse?

How violently does it blow? Is the glass shattered or blackened? If not, then I would guess a 2A fuse would hold. If it does, then it's blowing at a lot more than 2A, indicating a short circuit somewhere in the player.

What do the markings (on the unit near the holder, and on the original fuse) say? 'F' means a fast-blow fuse, 'T' means a slow-blow (and FF is very fast, but that's not the one you're looking for here). So if the original fuse says '2AT' on it, then you need a slow-blow fuse.

If the "SA" is inside a three-quarters circle, it almost certainly is "CSA", which is, loosely speaking, the Canadian analog to the circled-UL that indicates Underwriters' Laboratories approval.

I found a device (an electric-blanket type thing) with the CSA approval logo on it, scanned it, and extracted the CSA logo from it so you can see what it looks like. A jpeg of the result is up for pseudo-web fetch at http://216.46.5.7:27110/ - at least until next reboot, but that machine doesn't normally reboot often.