Slo-blo fuse

[Alex Eisenhut]

I'm repairing my Dad's 1959 Grundig cabinet radio. The fuse is still good but I can't figure out what type it is. It must be a slo-blo of some kind to allow the filaments to heat up I guess, but I've never seen a 5mm x 20mm 1 amp fuse built with two tension springs.

I usually see that kind of arrangement in higher current ratings.

Would a modern slo-blo fuse work as well? I'm asking because I recently found out there are no more electronics stores near me or my Dad's place that sell fuses anymore, so I have to use my limited stock of 5x20 fuses.

I can see the fast acting type just has a hair-thin filament, and the slo-blo variant has a blob of solder or something on the filament.

Are there different ratings of slo-blo, like even slower for tubes?

[bob91343]

What are the markings on the end caps of the fuse?  There are variations in slow blow fuses so you have to know the details to get the proper part.

[Vovk_Z]

I'm 95% sure it can be replaced with any actual 1A slow-blow fuse.
The spring there can be for some technological purposes in the 1970s.

[bob91343]

I believe the 'spring' is actually a calibrated heat buffer to control the speed of temperature rise.

[Alex Eisenhut]

It's also possible it's not a 1A fuse, just something someone slapped in there once.

The terminals are corroded and the fuse markings are not legible because of the corrosion, probably from watering the plant that my Mom left on the cabinet..

[ejeffrey]

Just measure the current and the inrush duration with a meter and pick an appropriate fuse?

[bob91343]

Look up the model and Google it to find the diagram, which should give the info you want.

[james_s]

I've seen slow blow fuses that had a spring in them sort of like that, the ones I had used a soldered joint inside and when the element heats up enough to melt the solder the spring would pull it apart. It probably isn't critical though, fuses are not precision devices.