What fuses can I use in a power supply?

[Dang]

Hi, Merry Christmas and a Happy New Year to you all. I have a power supply from an LG LCD Tv that had a blown/shorted main capacitor taking out the main input fuse, the cap is now replaced but I don't have the right replacement fuse(a leaded 5amp 250v), so in it's place, for testing at the moment, I have used some old brackets from another dead power supply and used a 5amp, 250v mains plug type fuse, Tv now turns on so all is fixed, all I want to know is can this fuse be left in place or is it best to change it, if it needs to be changed back to an original type, what would be the difference between the two to dictate that? thanks again, Andy.

[tw2005]

Re: What fuses can I use in a power supply?

Hi, Merry Christmas and a Happy New Year to you all. I have a power supply from an LG LCD Tv that had a blown/shorted main capacitor taking out the main input fuse, the cap is now replaced but I don't have the right replacement fuse(a leaded 5amp 250v), so in it's place, for testing at the moment, I have used some old brackets from another dead power supply and used a 5amp, 250v mains plug type fuse, Tv now turns on so all is fixed, all I want to know is can this fuse be left in place or is it best to change it, if it needs to be changed back to an original type, what would be the difference between the two to dictate that? thanks again, Andy.

I think so long as it's the same current, voltage and package type it should be ok. Don't use a glass type in place of a ceramic though as the glass can explode when the fuse blows. there's also slow and fast blow fuses too.

[mariushm]

Re: What fuses can I use in a power supply?

If the current rating is too high, the fuse will be useless. Make sure it's as close as possible to the original rating. It should be printed on the PCB as it's quite important information.

Also make sure to get time delay fuse if it says so, the time delay fuses have a T printed on them, like T4A250V for a 4A 250v time delay fuse. Time delay means the fuse can allow much higher current for a bit of time before blowing up, which is useful for switching power supplies that can pull a lot of energy from the mains when plugged in to fill the large mains capacitor and start everything up.

[Dang]

Re: What fuses can I use in a power supply?

If the current rating is too high, the fuse will be useless. Make sure it's as close as possible to the original rating. It should be printed on the PCB as it's quite important information.

Also make sure to get time delay fuse if it says so, the time delay fuses have a T printed on them, like T4A250V for a 4A 250v time delay fuse. Time delay means the fuse can allow much higher current for a bit of time before blowing up, which is useful for switching power supplies that can pull a lot of energy from the mains when plugged in to fill the large mains capacitor and start everything up.

Ahh, as suspected hence asking, it was a T5A250V ceramic that had blown so I guess a normal mains plug fuse won't cut it, thanks for the help guys, Andy.

[Alastair E]

Re: What fuses can I use in a power supply?

Only three words apply to fuses--

The Right One!

[tom66]

Re: What fuses can I use in a power supply?

The fuses used in mains plugs are designed to protect the plug and the wiring only! They are not intended for internal use in appliances, and the correctly rated electronic fuse must be used inside the appliance.

They are designed to tolerate overloads for a considerable amount of time as cables typically can sustain such overloads temporarily. For example, a typical BS1363 fuse ("UK plug fuse") rated at 13A will operate up to 400 seconds at 30A load. Consequently they are also quite "slow" fuses when a high overload event might occur (such as in the case of a semiconductor failure.)

A time delay fuse will blow in typically less than 30 seconds at twice rated load, and in under one second at 10x rated load. Typically, faster than the breaker can trip...and faster than the '1363 fuse.

[Dang]

Re: What fuses can I use in a power supply?

That's interesting, the fuse was only used for about 30 seconds just to see if the Tv worked, which of course it did, I did try Maplin for the right fuse but they don't stock it as with many "usual" things, go figure.