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Discussion Starter #1
I think I should have an extra set of fuses for my amp (Fender Twin). The owners manual says I should have:

F200: T4A 250V
F201: T5A 250V
F1 & F2 T100mA

I'm not an electrical engineer, so where can I find this stuff? (Montreal area.)

Bogoboy
 

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Go to radio shack/ The Source or even Canadian Tire, You will need to know the casing size which would be something like GMA or another three letter symbol plus the voltage in this case 250 V and the amperage rating as in your post 4A, 5A and 100mA. Take this info to there service person and they should be able to help you out.
 

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Short fuse or long fuse? :)

The prefix with Bussman Fuses (major brand and everybody can recognise and convert their numbers) will be MDL.

So you're gonna ask for an MDL 4 amp and MDL 5 amp.

The "T" in the spec means slow-blow. Most of these glass fuses are AGC series which means fast blowing. The slo-blow series is MDL. My memory was better before the kids came but I believe GMA refers to a 5mm x 20 mm European size of fuse, a bit smaller than you usually find in American made vintage amps.

Many tube amps use slo-blow fuses. When you first turn on the amp there's a big surge to get things started but only for a fraction of a second. The filter caps in the power supply are drained and look like a dead short until they start to charge up. The tubes are cold and they also draw gobs of extra current until they start to warm up and glow.

A normal fast blow fuse will panic and crap out too quickly. Slow-blow fuses are more laid back and allow the initial surge to pass through without getting upset, only blowing when there is a sustained overload.

Any home owner with a sump pump in the basement knows that you need a time-delay fuse to allow the motor to start up. It's the same principle here.

You wouldn't believe how many Marshalls I get in where the player changed his own fuses and bought fast blow 'cuz he didn't know the difference! I usually just charge him for the fuses and quickly send him on his way. I don't make any money on that call but it buys a lot of good will when he really has a problem...
 

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Too much info...

bogoboy said:
Thanks all

I'm still a bit confused.

Bogoboy
Yeah, that was a lot thrown at you all at once. Let's see if I can pare it down to the essentials.

Fuses are chosen by amperage rating. 5A means 5 amps.

Fuses come in many different shapes and sizes. Yours are 1/4" x 1 1/4".

There are 2 overall types - fast blow and slow blow. The "T" in your part number means slow blow.

Ask the store clerk for a glass fuse, 1/4" x 1 1/4", slow blow in 4 amp and in 5 amp. The 100 ma is the exception. It should be fast blow.

Good luck!
 

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Discussion Starter #6
Thx Wild Bill

Thx once again for your help. So let me see if I got this correct... T means slow blow-is there a code for fast blow?

Bogoboy
 

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No news is good news...

bogoboy said:
Thx once again for your help. So let me see if I got this correct... T means slow blow-is there a code for fast blow?

Bogoboy
Fast blow is the "normal" type. If they don't tell you then it's always a fast blow.

Slow blow fuses are for "special" cases, like tube amps! So they have to make a point of indicating it to you.

If you look at the insides you'll quickly see that the fast blow type have a solid and probably thin wire inside. The slow blow kind will have the wire wound into a thin and springy looking spiral.
 
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