View Single Post
  #13   Report Post  
Posted to
[email protected] is offline
external usenet poster
Posts: 1,625
Default A guide to fuse replacement

Coming very late into this....

Fuses are very simple beasts made complicated by a fundamental lack of understanding.

a) The nature of the load. A purely resistance load is entirely different from a motor load. Both of which are different from a filament load.
b) How inrush current works. A purely resistance load has a massive inrush until the resistance element heats up - whereupon the load drops in proportion to the temperature. An AA5, for instance, is essentially a dead-short at turn-on. As are most tube loads.
c) The differences between motor loads, filament loads and electronic loads..
d) Rated Operating Voltage. Fuses rated below 240V are to be taken with much salt.
e) The differences between a standard fuse, a fast fuse, a slow-blow fused and a dual-element fuse. READ THE OPERATION TABLES!

And, unless you have no investment in the connected load or its fate whatsoever, eliminate all slow-blow AGC fuses from consideration - full stop (the one with the wire element wound around a ceramic rod)!!

From here, do your own research. For the power-supply in question, I would suggest starting with a 20A DE Fuse rated at 250V. NOTE: Many AGC fuses are rated at only 32V. Avoid them. If this blows consistently, only then would I suggest moving to a 25A DE Fuse.

Peter Wieck
Melrose Park, PA