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10-13-2018, 07:16 PM
Hi Guys
ALL fuses should be internal.
Generally, external fuses make it too easy for the equipment operator to install the wrong size fuse and cause more damage or even a fire, after the fuse has blown for some reason. people will do desperate things in unexpected circumstances, like wrapping the dead fuse in foil and re-inserting it. In older equipment you might find an internal fuse wired in series with the panel fuse as a means to provide protection from the user
TUT3 refers to Keystone 4245 fuse clips, which hold a 1.25" x 0.25" fuse and mounts in four eyelets. Takes up a lot of space, but that is what we started with in the hand-wired amps. This is a unitised piece with a narrow fibre-glass strip with two fuse clips on it - a bit more rigid than using the bulk clips, although you can do that easily since your eyelet boards are likely glass-epoxy; mine were Teflon, so the added rigidity for the fuses was welcome.
To some extent, any PCB-mountable fuse clip can be used in eyelets. Keystone has bulk clips to fit 1/4" fuses and for 5mm:
1/4" dia - 3514, preferred, 3529, 3515, 3516P
5mm dia - 3517, 3518P
The preferred part has 0.25" long tabs to go into the eyelets, where everything else is 0.14".
Depending on how many fuses you intend to install, it might be better to buy unitised fuse holders and solder them to eyelets or to printed traces just for this part of the amp. The latter approach opens up more choices of fuse and fuse holder. There are also fuse blocks, which are rigid material with a number of fuse positions where the clip has a wire solder lug.
I've built amps where there were eleven fuse holders, which makes it very appealing to use 5x20mm fuses and PCBs. The 5x20mm is universal. Even most US builders use this size now instead of the 1.25" x 0.25" types.
ALL fuses should be internal.
Generally, external fuses make it too easy for the equipment operator to install the wrong size fuse and cause more damage or even a fire, after the fuse has blown for some reason. people will do desperate things in unexpected circumstances, like wrapping the dead fuse in foil and re-inserting it. In older equipment you might find an internal fuse wired in series with the panel fuse as a means to provide protection from the user
TUT3 refers to Keystone 4245 fuse clips, which hold a 1.25" x 0.25" fuse and mounts in four eyelets. Takes up a lot of space, but that is what we started with in the hand-wired amps. This is a unitised piece with a narrow fibre-glass strip with two fuse clips on it - a bit more rigid than using the bulk clips, although you can do that easily since your eyelet boards are likely glass-epoxy; mine were Teflon, so the added rigidity for the fuses was welcome.
To some extent, any PCB-mountable fuse clip can be used in eyelets. Keystone has bulk clips to fit 1/4" fuses and for 5mm:
1/4" dia - 3514, preferred, 3529, 3515, 3516P
5mm dia - 3517, 3518P
The preferred part has 0.25" long tabs to go into the eyelets, where everything else is 0.14".
Depending on how many fuses you intend to install, it might be better to buy unitised fuse holders and solder them to eyelets or to printed traces just for this part of the amp. The latter approach opens up more choices of fuse and fuse holder. There are also fuse blocks, which are rigid material with a number of fuse positions where the clip has a wire solder lug.
I've built amps where there were eleven fuse holders, which makes it very appealing to use 5x20mm fuses and PCBs. The 5x20mm is universal. Even most US builders use this size now instead of the 1.25" x 0.25" types.
