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Ampeg V4 internal fuse blown still working

Discussion in 'Amps and Cabs [BG]' started by DudeLeap, May 27, 2016.

  1. DudeLeap


    Feb 11, 2013
    Hey everyone, I have a Magnavox era V4 that has a blown internal fuse but still turns on and functions fine. I was wondering if anyone has dealt with this before or if anyone with a v4 could post up pictures of the inside of their amp so I could check the fuse wiring. The external fuse is good and the standby light doesn't turn on.
  2. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    The power and standby lights can be problematic, if the amp is running fine the light probably isn't related.

    I've read differing opinions on the internal/external fuses, some people say the internal is a backup for the external but I've also seen that it was added for the courtesy outlet. Either way, are you sure the fuse is blown? If it was shorted or bypassed that could explain things?

    I don't have a picture of the fuse in my V4 handy but here's the wiring for my B25B with a similar internal/external setup. I soldered in the internal fuse as it was missing from the amp when I got it (you can see the tag noting that it should be a 6A fuse in there).

  3. DudeLeap


    Feb 11, 2013
    I'm positive the fuse is blown and I'm not sure if it's been bypassed or not but that would make total sense. I'll check the courtesy outlet later to see if it's getting power and put a new fuse in. Thanks for the info and picture I'm still new to these amps so any info is helpful!
    Last edited: May 27, 2016
  4. I had a '73 Magnavox V4-B and it was for the convenience outlet.

  5. blubass


    Aug 3, 2007
    Modesto Ca
    Current: Blackstar, DR strings, Nady. Previous endorsements with: GK, Rotosound, Ernie Ball, Cleartone, EMG, Dean, Dava Picks, Rebel Straps, Dickies
    By definition a blown fuse is an open in the circuit, and any open in a circuit means no current flow. If the fuse is blown, and the amp works, it's absolutely being bypassed.
  6. That fuse does not feed the amp circuits, it is protection for the convenience outlet only.
  7. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    To give a definitive answer I checked our powder room. The conveinience had no fuse whatsoever!! :D
  8. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Makes sense as to why it would work without that fuse. From the schematic it looks like the two fuses are in series but from how they're wired in the operation seems a bit more clear
  9. DudeLeap


    Feb 11, 2013
    Just put a outlet tester on the convenience outlet and it showed power going to it. I'm going to have to open up the head again to see what's going on with the wiring. I'm certain the fuse is blown because I can see the break, starting to think it might be bypassed.

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