How often do fuses blow?

Discussion in 'Amps and Cabs [BG]' started by nightcityburn, Aug 5, 2009.

  1. The title says it all.

    How often should I expect a fuse to blow on an amp?

    I had my first one blow last night, and am now really curious as to how often to expect it, if at all.

    Mine blew immediately after a guitar player plugged his head into the same power strip I was plugged into, and I didn't realize it until this morning that it was the problem

    Just want to get a feel how often it happens. I am currently gigging 4 to 5 times a week, but generally at least twice.

    Thanks for the input.
  2. Selta


    Feb 6, 2002
    Pacific Northwet
    Never, unless there's a problem.
  3. toomanybasses


    Feb 20, 2009

    Is this a new amp (to you)?
  4. flea claypool

    flea claypool

    Jun 27, 2004
    ideally they dont have a time line,

    fuses blow under fault conditions to save the gutts of your amp..
    i always pplug into a surge protector.. what kinda conditions where you playin in??
  5. Selta


    Feb 6, 2002
    Pacific Northwet
    For what it's worth, it sounds like you may have just had some surge when he plugged in his amp to the same circuit. Kind of wonky as it shouldn't happen, but, it could.
    Personally, I'd still be going over the amp to make sure nothing else is going on inside. Then put in a new fuse and see what blows the magic smoke :).
  6. I've been gigging for over twenty years and haven't blown one yet.
    What happened in your case is that the voltage in the building was low. Your amp was on already and drawing current even just sitting there.
    When the guitar amp was switched on, it momentarily drew enough power to lower the voltage even more, maybe below 80 or 90 volts. Seen it happen.
    When this happens, your amp's circuits increase current draw, to compensate for the low voltage, and this blows the fuse.
    So check voltage, and turn your amp on last.
  7. Sneakypete


    Jul 22, 2009
    Make sure the new fuse is the correct current rating and type - usually slow-blow or time-lag (T). The wire in the fuse cartridge warms up and expands a little every time you switch on - but as both ends are trapped by the caps this means it has to bend a little - after a long time you may get a little metal fatigue and lose a fuse but it should be very rare. Usually, but not always, the type of fault that blows fuses occur at switch-on-from-cold as the inrush current finds the weak spot. Is the blown fuse black on the inside of the glass or is it just like a broken wire?
  8. The fuse blew black and also had a broken lead.

    The amp is new to me, but I have played about 5 amps and never had a single fuse blow in 5 years.

    I picked up a pack of fuses from the local auto parts store to get me by until I get to a music store.

    I am not too worried yet, but as I start gigging it a bit more, I will see if the problem is recurring.

    Other than that, the guy I traded from gave a me a back up to go on tour for the next 10 days with. Super nice guy from TB. I love this place.
  9. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Fuses............ Simplest darn thing on earth.... but the number of details is actually huge.

    Long story short.....

    Ideal: the fuse never blows unless there is a problem.

    Reality: Fuses differ, and the very same type fuse by a different manufacturer may actually act different. Some will blow about the 100th time the amp is turned on, others will last the life of the unit, despite being the same type and rating (but from different makers).

    Your fuse probably blew due to a surge, possibly caused by the extra amp drawing down the voltage when it was turned on... the surge as the voltage came back up after that might have done the deed. Possible your amp would have blown that fuse when turned on in another few days anyway.

    Choosing the fuse when designing a product seems like a no-brainer, but it may need some consideration to avoid having it blow some time later when the amp is turned on.

    We had trouble with that for a while, before we established a definite way to choose the fuse rating, and stopped the purchasing folks from considering all brands as totally equal and interchangeable.

    I'd give ANY amp that blows a fuse ONE more chance...... put in the same rating, type, (and brand if possible) of fuse, and try again. if it blows a second fuse immediately, or pretty soon, it needs repairs. If the new fuse holds, just use it.

    Lots of people are convinced that if it blows, there is automatically a problem, and any more tries will just do more damage. Can be the case, but why take in the amp and find out for $25 or more that it was just a fuse? ONE more try won't do much if any more damage in 99% of cases..... and if the amp has a problem, it already needs repair.
  10. toobalicious


    May 6, 2008
    triad, nc
    and be very mindful of using a "not right" fuse in a pinch simply because it fits. glass auto type fuses are likely to be rated from perhaps 10-30 amps (or more, maybe), whereas the spec for the fuse in your amp probably calls for more like 3-4 amps (or less, but obviously will depend on which amp we are talking about). for example, my mesa 400+ takes an 8 amp slo-blo, while my fender bandmaster only requires a 2 amp slo-blo. in either case, though, a 30 amp auto fuse is not likely to do diddly squat in either of them were there to be a fault--- at least not until things get *really* out of hand, which might very well be too late to protect anything. the old multi-hundred-dollar part sacrificing itself to save the $0.50 fuse scenario.
  11. Pilgrim

    Pilgrim Supporting Member

    Yes, the difference between a conventional fuse and a "slo-blo" is important!

    Make sure to replace with:

    - The same amperage (not higher!)
    - The same type, conventional or slo-blo
    - The same length

    If you have any doubts as to the correct fuse, look for labeling on the amp next to the fuse holder; if no info, check your owner's manual; if no manual, go online to see an owner's manual or specs. This really does matter if you don't want to keep popping fuses.
  12. They only blow when you need them to be there for you :ninja:

    This is a major reason i've stuck with solid state (Sunn, Acoustic, Kustom and Peavey).
  13. Selta


    Feb 6, 2002
    Pacific Northwet
    What does solid state have to do with *anything* here?

    OP doesn't even state what his amp is... looking in his profile, I'm guessing it's his Shuttle 6.0, which, is solid state. Still doesn't matter one way or the other though...
  14. No this is my 750x I just traded my shuttle for.

    Jerrold definitely helped a ton.

    That being said I did replace it with the correct fuse as far as amp ratings go. 10 amp fuses for both fuse slots.

    Thanks for all the help. Keep the discussion open as I think this will really help other peoples.
  15. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    "Auto-type" fuses in the physical sizes that fit in your amp, besides being usually larger amperage than you need, have another very serious problem. Its a good thing they are disappearing in favor of the color-coded "blade" type that won't fit in your amp....

    The problem is the voltage rating...... A fuse is ONLY guaranteed to blow "all the way open" within its voltage range, which is 32V for an auto fuse, and generally 125V or 250V AC for the fuses you would need.

    If you are going to have a fuse, it needs to actually "open" the circuit if there is a problem. So using an "auto" type fuse may lead to the fuse "blowing" but not actually completely disconnecting the circuit.... That could cause added un-necessary damage if the fuse blows in case of a real problem.

    Use the right type.
  16. Expect the fuse to blow every time you exceed the power output, short the power cable etc. !!! Is your amp digital?you could amp have a ground fault detector you said the guitarist plugged into your strip then it blew?