What FT means in an SMD fuse?

Website

would suggest that it is a time delay ("T") 0. 5A type ("F")

Arfa

Yuki asked:

The noise it makes when it blows!!!

Then a slow blowing would be FFT or FFFT

greg

Thanks,

I'd found a spec sheet from Littelfuse that uses TF (instead of FT) for a 500mA slow fuse but not sure if the markings mean the same in all manufacturers.

I rarely come across surface mount fuses, but for a more general query. Has anyone tried cracking open a SM fuse to see if the size of any remnant film can give an indication of amperage. ?

Where you cannot be sure, I would wire off of the pads to a conventional , but lower amperage fuse, than the 0.5A that it maybe in this case. Then see how it blows if it blows. Then replace with a smt device when confident.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

manufacturers.

see

By "see" i mean if you wire in a glass cased 100mA fuse and you see it glow orange before fusing then 500mA rating is probably about right. If it blows very quickly and intensly white or green then still an underlying fault or a fuse rating higher than 500mA

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

This particular one is encapsulated in transparent resin and looks like having a blob of tin in the center, no glow here for this reason and because it's located in the phone line input of and ADSL router for protection.

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query.

remnant

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it's located

Since this fuse is in series with the telephone line the telco line current maximum will be in the order of 100mA. My opinion is that any SMD delay type fuse of 200mA - 500mA will be adequate. I would first be wondering what caused it to blow. Usually, the line interface is current limited so I doubt the current which blew the original would come from the exchange, but I could be wrong there.

The cause is known, it was a nasty electrical storm with several direct hits in phone and power poles. A lot of phone line connected equipment was killed that day.

I have fixed this problem before but with proper labeled fuses in the board.

Now my problem is sourcing it for a reasonable cost as I'm far from decent component stores. I somebody can suggest a supplier I'm located in southern Spain.

You could solder leads on a glass tube fuse and use that to replace it. That should be much easier to find than a SMD fuse. DSL Modems usually have extra room inside so space shouldn't be a problem.

Mike

SNIP

decent

southern

Try

Littelfuse 430 series (SLO_BLO) 250mA

For more supplier options in Spain Google 'smt fuse site:.es'