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Fuses for SVT

Discussion in 'Amps and Cabs [BG]' started by drd07, Apr 2, 2004.

  1. drd07


    Jan 19, 2003
    I have a late 70's Ampeg SVT. What kind of replacement fuse does it take and where can I get one? Does anybody know?
  2. The external fuse is a 10A normal fuse.
    The internal fuse is a 1.5A Slow-Blow fuse.
    You should be able to find these at most hardware stores.

  3. I think the 70's SVT did not have the internal slow-blow fuse.
    After looking at a schematic it looks like it just has the 10A normal fuse in the external holder.
  4. JRB

    JRB Supporting Member

    Oct 21, 2003
    Oakland, CA
    If you can't find then at a hardware store you can order them online. On site that has almost everything is digikey. Have a great day.
  5. drd07


    Jan 19, 2003
    Thanks for the info. I will head on out to the hardware store to pick up a 10a fuse. Thanks!
  6. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    All of my 70's SVT have internal fuses. I believe they are 15A normal fuses, not slo-blo. The external fuse is a 10A.
  7. drd07


    Jan 19, 2003
    Are the internal fuses easy to replace? Are they hard to find in the amp?
  8. The internal fuse should just be clipped into a fuse holder, you just gotta open the amp up to get to it.

    As for the internal fuse value, it doesn't make any sense for there to be a higher rated internal fuse (15A) placed after the external fuse (10A) in the circuit.

    The schematics I have that show an internal fuse (Current SVT CL) show it as a 1.5A Slo-Blo.

    You might want to check that internal fuse value again, it should be right on the end cap of the fuse.
  9. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    It makes total sense that the internal fuse is of a higher rating - it's a backup for the external fuse... Suppose the amp is blowing fuses, so some brainiac sticks a 30A in the external holder. The 15A is there as a backup and will protect the amp.

    And I seriously doubt the internal fuse in any SVT is 1.5A, slo blo or not. An SVT pulls 8 amps at full tilt!

    All of my early 70's heads have the internal fuses soldered in between the external fuse jack and the accessory power outlet on the back of the amp, which is also where the power cord is connected.
  10. Hey, I'm just posting what the schematic says.
    I don't pretend to be an expert.

    I attached a snapshot of the schematic where you can clearly see that the internal fuse is a 1.5A Slo-Blo
  11. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    Can you show me the rest of the schematic?
  12. You have a PM
  13. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    Aha, I see it now - that 1.5A fuse in your amp feeds the filament transformer. I knew there was no way it could feed the power supply like a 70's head does, the fuse would blow the instant you flipped the standby switch!
    So you are correct, the internal fuse in an SVT classic is a 1.5A slo-blo, and I was correct, the fuse in a 70's SVT is a 15A non slo-blo.

    You learn something new every day.
  14. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Just for the record, "fuses ain't all fuses".

    The fuse you use should be a standard power type rated at least 125V.

    Old cars used the same style fuse, which is visually almost the same, except it was rated only 32V and was marked that way. Lots of hardware stores carry both, and they don't always know which is what.

    DO NOT use the "car style" low voltage fuses for AC power. There is no guarantee that they will actually work correctly. If not, they might fail to open the circuit when they need to and might cause additional damage or injury.

    The correct type will be marked on the box and on the fuse with the current rating, a UL mark, and a rating of either 125 or 250 volts.

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