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Nomination: Worst fuse holders ever

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  • Nomination: Worst fuse holders ever

    A couple of days ago, I spent about an hour locked in battle with the Mains and H.T. fuse holders on a Marshall JCM800 head. The amp was working--I was simply checking the fuses to make sure the right values were installed, but when I tried to power the amp back up, there was no power. The fuses were good, but the fuse holder circuits were open.

    These holders are snap-in types with a metal sleeve that fits over the fuse and a spring in the end-cap. I think the idea was that the spring presses the metal sleeve and spring against another contact inside the holder. The problem seems to be that if there's ANY binding between the plastic end-cap and the metal sleeve, no contact is made.

    I finally got them to work by 1) seating the fuse completely in the holder (not the cap) 2) pressing the sleeve into position around the fuse and 3) fastening the end cap with spring inside. I can't imagine that this was how they were designed to work. And, of course, the springs have an annoying tendency to fall out of the end caps.

    My conclusion was that these were an attempt at a clever new fuse holder design, but I've never had this much trouble with one in all the years I've been working on electronics.

  • #2
    Or the particular holder in that amp was defective. Some little something was bent inside, or a little piece fo metal somewhere was broken off, or whatever.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      I hate the practice of not using fuse holders at all but instead soldering the fuse in place.

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      • #4
        Originally posted by teemuk View Post
        I hate the practice of not using fuse holders at all but instead soldering the fuse in place.
        Preferably with an opaque sleeve over it so that you can't tell whether it's good without a meter. I guess the upside is that it's truly an idiot fuse. Most people won't even notice it....
        ST in Phoenix

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        • #5
          Originally posted by Enzo View Post
          Or the particular holder in that amp was defective. Some little something was bent inside, or a little piece fo metal somewhere was broken off, or whatever.
          It was BOTH holders. I think the design would work if the metal sleeve vital for making contact moved freely inside the plastic end-cap, but it's possible that the plastic warped slightly over time or that the sleeve got bent at some point. But my point is that even an imperceptible distortion of the metal sleeve or the end cap makes the holder not work like it's supposed to.

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          • #6
            Originally posted by teemuk View Post
            I hate the practice of not using fuse holders at all but instead soldering the fuse in place.
            How about using no fuses whatsoever--like the Dynaco PAS preamps?

            Do I smell something burning....

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            • #7
              Just as all 1/4" plugs aren't quite the same diameter and length, maybe some fuses are just enough off of the original fuseholder spec to cause problems.

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              • #8
                Why not breakers?

                Weber sells 'em for the same price as a fuseholder.
                You can't put the wrong value in, or defeat them without opening the chassis.
                You can't run out of spares.

                They're marginally larger, but not longer or wider than a traditional fuse holder.

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                • #9
                  Annoyances.org - How many forum members does it takes to change a light bulb?
                  (substitute fuse for light bulb in the above )
                  "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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                  • #10
                    That's great.
                    Education is what you're left with after you have forgotten what you have learned.

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                    • #11
                      Originally posted by teemuk View Post
                      I hate the practice of not using fuse holders at all but instead soldering the fuse in place.

                      My friend who played bass with me in high school never fails to remind me of when I put tinfoil around the fuse in his Bassman when we were 15.

                      Weber sells breakers? great. I need one for a Randall I'm working on.

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                      • #12
                        Originally posted by drewl View Post
                        My friend who played bass with me in high school never fails to remind me of when I put tinfoil around the fuse in his Bassman when we were 15.
                        Every once and a while an amp came across my bench with 1/4" aluminum dowel cut to the length of an AGC fuses in the fuse holders. The PT was always bad of course. BTW, I always like pigtail soldered in fuses. There are no bad connections and it forces you to use a meter and not rely on looks. I guess it's a pain if you have to pull the chassis. If the chassis is out I prefer it. Besides, you can always install a twist type fuse holder like they use on car stereos.

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                        • #13
                          Had a burnt up amp come in once with a section of 1/4" bolt sawn off and clipped in the fuse holder. but it was good audio quality stuff, it was one of those gold plated 1/4" bolts like they do power connections with in car stereos.

                          I don't mind pigtails, but for situations I have a box of twin fuse clips - back to back clip sets. You clip it onto the body of the open pigtail fuse, which is the size of a common fuse. Then in the empty clips on the other side of it, you snap in a common fuse. Takes two seconds, no soldering. yes of course you can abuse it, but it gets you going fast.

                          Mouser 504-3434. A drawing of it is on the Bussmann fuse holder page, item N on mine.
                          Education is what you're left with after you have forgotten what you have learned.

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                          • #14
                            That's basically what I meant with the twist fuse holder and an alligator clip at each end.

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                            • #15
                              re fuse to be mocked!

                              circuit breakers can be great, but often its just the house fire they avoid. The cheap thermal (bi metallic) circuit breakers usually used are designed to trip within one hour at 140% of its rating (?!!)

                              Much better are magnetic circuit breakers that trip in 10 ms or less, or hybrid thermal/magnetic...guess which cost more?

                              A central fuse block (3-4 fuses, internal) is good for most amps but the panel mount units can be convenient (and/or a pain).

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