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...
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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