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Ampeg V3 MTI main fuse rating?

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  • #1

    Ampeg V3 MTI main fuse rating?

    Here is a link to the schematic (thanks again Steve L!)

    http://music-electronics-forum.com/t45946/

    The main fuse and cap to the holder are missing. It's the fuse that is accessed from the back. There is no writing on the amp telling the value.

    I tested the amp for power, for about a second, without tubes (speaker attached) and a 2 amp fast fuse. The lights came on.

    I was thinking a 2 amp slow blow to try?
    Is that safe to start? I've never seen lower for that fuse, only 2 and higher.

    I don't know the power transformer voltages either. ?

    When I get the new fuse holder and fuse in I will test then.

    The transformer has NTK 270922 on it, if that means anything?

    Thanks,
    Kirk
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  • #2
    A 2 amp fuse is fine for testing.

    If you have a setup to test the overall amp current, that would be the final answer.

    Hint: I use the "Kill-A-Watt"
    Kill A Watt Meter - Electricity Usage Monitor | P3

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    • #3
      Is the internal fuse in series still there (inside chassis)? It will be a bit larger value than the outside fuse. It is there in series as a backup in case someone puts a big fuse or tinfoil at the outside fuse.
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


      ​

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      • #4
        I will look into that Kill A Watt meter. It would be handy.

        The bigger, in series, fuse is there. It's soldered in and I can't read it without removing it. It looks beefier than any 2 amp I've seen though. Probably higher. That's why I tried it out with the 2 amp fast. I figured if there was a PT short it would probably go quick.

        It looks nice inside, the only pcb is preamp stuff that the pots connect to. It say V3, V7(100 Watt version) on the pcb. The rest is wired.

        When I get the fuse holder I will report back.

        Thanks

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        • #5
          I picked up a Kill-a-Watt, thanks for that hint!
          When I turn on the power, it goes up to about .75 amps
          Then it levels off around .45

          When I turn standby off it goes up to 1.15 (with the power tubes in and speaker hooked up). It doesn't do the spike in current and level off like the power switch. It just rises up to 1.15 amps.
          Is that normal? I thought it would spike, then level off a bit. When I play it hard, it goes up to about 1.25.

          Thanks,
          KC

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