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Fuse question.

Lil_Guppy

New Member
Recently I purchaced a Powertech MP3090 power supply. As it came with no spare fuse for the 240VAC mains socket, I was going to buy a set of spares for it. The fuse is a T5A L250V. Obviously it is a 5A 250V fuse, but is it a slow or fast blow? I hade a bit of a look on the 'net, but most of the info is pretty vague. Any help would be much appreciated.
 

Klaus

New Member
the "T" would stand for slow blow, IMO.

you can also sometimes see what kind by whats inside the glass tube. If it not a glass tube type disregard the following:
Fastest fuses have just a thin wire link.
med slow have a thicker wire link with a tiny spring at one end.
Slowest fuses have the element spirally wound around a thin former.

Klaus
 

Lil_Guppy

New Member
Hmmmz... According to this manual (for another product) the T5A L250V is a slow blow fuse.

FUSE
If the fuse blows, replace with a fuse of the correct
type only; use of any higher amperage value will
void the warranty. FUSES ARE FOR YOUR
PROTECTION—NEVER SUBSTITUTE A FUSE
OF A HIGHER RATING, OR BYPASS IT.
All fuses are the "Slo-Blo" type, sized at 5mm
diameter x 20mm:
Model, 100-120 volt, 220-240 volt
RA150, T3.15AL250V, T1.6AL250V
RA300, T6.3AL250V, T3.15AL250V
RA500, T10AL250V, T5AL250V
As for what the fuse looks like, it is a thin and about 0.8mm wide, no spring bit. It is much wider than the 5A 250V fast blow fuses I have, but has no spring/spiral look like the slow blow fuses I have. For the time being, I've put a fast blow fuse in there...
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Lil_Guppy said:
Recently I purchaced a Powertech MP3090 power supply. As it came with no spare fuse for the 240VAC mains socket, I was going to buy a set of spares for it. The fuse is a T5A L250V. Obviously it is a 5A 250V fuse, but is it a slow or fast blow? I hade a bit of a look on the 'net, but most of the info is pretty vague. Any help would be much appreciated.
'T' is anti-surge, 'F' is fast blow, and 'M' is a specific microwave spec fuse.

I replace and sell a LOT of fuses at work :lol:

As I understand it the 'T' comes from German?.
 

Lil_Guppy

New Member
So it is in fact a slow blow fuse? I guess I was a little confused by the physical appearance of the origional fuse, and the slow blow ones I have (which are spiral like). Are there any different types of slow blow fuses?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Lil_Guppy said:
So it is in fact a slow blow fuse? I guess I was a little confused by the physical appearance of the origional fuse, and the slow blow ones I have (which are spiral like). Are there any different types of slow blow fuses?
NO! - read my previous post! - it's anti-surge!.

There are various different types of anti-surge and slow blow fuses, some have a spring in them, some have a 'blob' on the wire, and some (particularly recently) have just a plain wire and no visible difference, apart from being clearly labelled 'T'.
 

Lil_Guppy

New Member
Well, now I am thoroughly confused :p So why are the T5AL250V's stated as slow blow in the PDF manual I linked to? At the moment, I have replaced the fuse with a 5A 250V fast blow. Is this going to be safe for the power supply, or is the worst that is going to happen is it blow more than usual. Can a slow blow be used in place? What's could happen if a slow blow IS used? What should I be looking when trying to find a proper replacement? That's basically what I want to know. Thanks.
 

Phasor

Member
Nigel Goodwin said:
As I understand it the 'T' comes from German?.
I believe the 'T' stands for "träge", which means slow or lazy. Not to be confused with "trage", which is to carry something.
 

Someone Electro

New Member
Fast fuses blow faster in a pulse.An 5A slow my not blow at an realy short 10A pulse.

if its going directly in to a transformer they a slow one wod do since trasfosmers wod take it.

so its wvwn safer to put in an fast insted of slow but dont replace an fast whith an slow.So it shod work normaly whith a fast one
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Lil_Guppy said:
Well, now I am thoroughly confused :p So why are the T5AL250V's stated as slow blow in the PDF manual I linked to? At the moment, I have replaced the fuse with a 5A 250V fast blow. Is this going to be safe for the power supply, or is the worst that is going to happen is it blow more than usual. Can a slow blow be used in place? What's could happen if a slow blow IS used? What should I be looking when trying to find a proper replacement? That's basically what I want to know. Thanks.
Fitting a fast blow in place of the anti-surge one will result in the fuse failing for no reason, usually at switch on. If anything it will be 'too safe', and you should make sure you have a number of replacements to hand at all times.

But for the third time! - YOUR OLD FUSE WAS ANTI-SURGE (SLOW BLOW), AND CLEARLY MARKED AS SUCH.
 

Lil_Guppy

New Member
It doesn't blow the fuse (fast blow) if I load the PSU with 6V @ 5A and then turn it on... Sorry about the confusion, there are several people telling me different things (not on here). So it is fine to use a slow blow as a replacement?
 

Exo

Active Member
Yes, it came with a 'T' fuse , so it's safe to replace it with a 'T' fuse of the same Ampérage.

The fact that the fast fuse doesn't blow is because of the load condictions.
If you were to use an inductor as a load (a motor for example) the fast fuse would blow.

If you're never going to put an inductive load, or a load that comes close to the supply's max, on the supply then the fast fuse will do fine to.
 

Lil_Guppy

New Member
Which brings me back to my problem... I can't find 'T' type fuses. The slow blow's I have have an 'S' prefix :? From a PDF on the Jaycar site:

"The two most common types are the standard or ‘fast acting’ (F) type, and the ‘Slow Blow’ (T) type, designed to tolerate a large number of ‘startup surge’ type short-term and modest overloads without blowing."

The 'S' type fuses I have a clearly marked on the box as slow blow. So is 'S' = 'T', or are there different types? Could it just be that the manufacturer of the fuses I have at the moment (Digitor) use an 'S' instead of a 'T'?

I must sound really stupid asking all of these questions. I just don't want to toast my shiny new power supply :oops:
 

Nigel Goodwin

Super Moderator
Most Helpful Member
You don't have your location filled in!, so we've no idea where you might be?, so we can't comment on your local situation.

In Europe I've never seen an anti-surge fuse with anything other than T on it.

There must be some local TV service companies where you live?, pop in and ask to buy a fuse - take your original one with you.
 

Exo

Active Member
Yes, Like Nigel sais, try going to an electronics shop nearby and show them your old fuse.

You can also order it online.

Lil_Guppy said:
I just don't want to toast my shiny new power supply
Fuses are meant to protect against fire and other things that can happen when the supply is shorted, they are NOT meant to protect the supply itself.
When a real short does occur it's very likely the supply will ge gone before the fuse pops.
If you want to protect the supply you'll have to add an electronic current limiter.
 

Lil_Guppy

New Member
Sorry, I thought I had filled out my profile. I'm from Australia.

I took the fuse into the local electronics store, and the guy said it was a slow blow fuse BUT he wasn't 100% sure because the physical appearance of the original was different from the slow blows fuses they had in stock. I recieved an email from Jaycar (they sell the same PSU) today and they say that the 'T' means slow blow fuse, but they did not say whether 'T' was the same as 'S'. I replied asking that question and am waiting for their reply.
 

Lil_Guppy

New Member
Yup, they are M205's. I have a box of slow blow fuses here of the correct rating. I think I was just confused about the physical appearance, and I didn't want to put a wrong type in. Thanks.
 

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