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Getting shocked: Peavey Century grounding help

Discussion in 'Amps and Cabs [BG]' started by russpurdy, Oct 19, 2013.

  1. russpurdy


    Apr 16, 2013
    Hey guys. I posted awhile ago about buying a peavey century head and decided to pull the trigger for 100 bucks. Came with a scorpion equipped 1x15 cab so I was happy with the deal.

    Anyways, there is a two position power switch with on-off-on modes. Manual says to just pick the one that doesn't cause hum. I'm assuming one is a ground lift mode? The ground prong on the power cable has also been pulled off. I'm going to get a new plug installed but does anyone know which position the switch should be in for proper grounding without the lift? I didn't get any shocks when I tried it out at the sellers place but I'm getting some small zaps at home. I won't be using it until the tech checks it but I'd like to know which option is which on the power switch. Thanks!
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Words of wisdom.

    Based on details that I linked below, the two positions of the switch swap the two power wires, and one wire has a capacitor to ground. In one position of the switch, the "hot" side of the mains will be coupled through that capacitor to the chassis of the amp, hence your shock. Any electrical leakage in the amp could also make it dangerous.

    A tech can fix this, probably by installing a correct 3-prong power cord and making sure that those capacitors are functioning properly.

    Power amp schematic


    Thread showing guts of Peavey Century. You can see that it's not a thing of beauty, but typical of amps made during that time period. The mains wiring right next to the output jack gives me the heebie jeebies.

  3. russpurdy


    Apr 16, 2013
    Thanks man, mine is actually a later model with a slightly different layout and I believe the mains are on the opposite side as the instrument input (hopefully :s) but I'm guessing the 2 position power switch does the same thing. Good thing a buddy of mine finally found a decent tech in town or else I'd be hooped.
  4. In the OLD days :rolleyes: that hurt. We used to lightly touch the strings and listen for a tick, if we heard one we would reverse the switch. The least hum and ticking sound would tell us the neutral was switched to chassis and we were "safe".
  5. russpurdy


    Apr 16, 2013
    Still hurts nowadays haha. Tech is gonna put a proper grounded plug back on and tell me which switch I should stick with as long as I'm using a properly grounded outlet.
  6. With a proper ground the switch position is redundant. The "death cap" is only in play when there is no ground. Many techs remove the ground cap when a 3 wire cord is installed. :)
    I only forgot to check my polarity switch once, took 117vac to the lips. I thought we had a brown out????
  7. russpurdy


    Apr 16, 2013
    So here is the deal....

    The tech wants 60-75 to replace the cord. It's already a three prong cord with the ground lug snapped off. I got the amp plus cab for a hundred so I figure I only paid fifty for the amp. If I go to Home Depot and get a new plug end and attach it that should help with my shock issue correct? The stock amp had a three prong cord but somebody broke the ground prong off. This should mean that if I regroupd the amp with a new cord end I may be able to solve my issue. Am I on track or way off?
  8. If you replace the plug it would be a good start. Our Home Depots have yellow "hospital" style plugs that I use when I make my own power cables. Don't buy the cheaper rubber versions, they are not much good.

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