I'm not so sure they are fused internally. I have owned a number of similar models and recapped all of them. I have not seen a fuse in one ever. I bought some fuse holders from Amazon and I add them to the power line. They are made from 10 gauge wire. My Palomar 225 draws just under 15 amps on SSB and will occasionally blow a 15 amp fuse. I put a 20 amp fuse in mine. Interestingly enough, I have been unable to find the fuse spec for any of these amps so I use my amp meter for "normal" current draw and just use the fuse that is the next highest one. There is a good amps vs cable size vs feet here https://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html . It shows that a 10 gauge wire is good for 20 amps as long as the wire is under 15 feet.Thanks! I have a this one and a Palomar that I inherited years ago, along with a President HR2510 and Ranger 2950. They have been stored in the attic of my shop for at least 10 years. I decided to see if they still worked, and after changing a couple of leaky caps and a speaker, the Ranger and Palomar came alive Saturday and I astonished my wife to be able to throw a little skip right of the bat, sitting in my truck in the front yard. Now she wants the Pres. in her car, so I plan to add this amp to it. There is no fuse holder, so I was curious as to what protection it needed. It is fed with 12 gauge wire, so there's that...