From: not.here@invalid.invalid   
      
   On Mon, 30 May 2011 22:46:12 -0700, Paul D. Spiegel wrote:   
      
   > What do RATS use as a "rule of thumb" to select a fuse for a power amp?   
   > In the past I've doubled the idle current, but honestly, that was just a   
   > guess.  How do you choose?   
      
   You need to look at what the fuse is going to protect, and remember that   
   the fuse rating is, nominally, the maximum that the fuse will carry   
   continuously without blowing. Fuses blow because of heat, they have a   
   reverse time characteristic. As the current increases they blow faster.   
   That affects how you use them. It's no use putting a quick blow fuse in   
   part of the circuit that is going to see large surge currents, likewise a   
   slow blow fuse in the cathode of an output valve would never protect it.   
      
   To find out the actual blowing point of the fuse you need to get it's   
   fusing characteristics graph. That plots current against time, with a   
   tolerance included. From that, and knowing the load that you want to   
   protect, you can pick the correct fuse.   
      
   Or you can measure the load and make an intelligent guess ...   :-)   
      
   --   
   Mick                      (Working in a M$-free zone!)   
   Web: http://www.nascom.info   
   Filtering everything posted from googlegroups to kill spam.   
      
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