short circuit problem

Discussion in 'General Electronics Chat' started by Thomas.R, Mar 21, 2008.

  1. Thomas.R

    Thread Starter Member

    Aug 16, 2007

    a while ago i posted a thread about an audio mixer that has a faulty Schottky-diode. I replaced the diode and tested it at home and didn't noticed anything. When I went to the rehearsal room and plugged the thing in, I noticed that the enclosure started making sparks. After that the fuse of the house tripped and all power was gone.
    what was the problem?
    some measurements i did
    the fuse of the mixer is not burned.
    the chassis was connected with the ground pin of the input of the power supply
    after i did this the house boss came in wondering what happened and told us that there was no ground on the electricity net in the basement (rehearsal room).
    So I'm asking myself, what happened there and should we plug our instrument amplifiers on an ungrounded circuit.

    i hope i made myself clear with my lousy English and looking forward to an answer

    ohh and i am still alive :)
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    A Schottky diode is a low-voltage device. It's not likely to have to do with your current problem. Something has made a path from the mains to the chassis.

    Do you have a meter? If the mixer's fuse didn't blow, the problem must be on the unprotected side. If your line cord is old, a short may be present in it, possibly where it passes through the chassis. Using a meter to look for low ohms from the line cord to the chassis may locate the problem.

    If you saw sparks, there should be some signs of the problem - burn marks or bulges in the line cord.
  3. Nomad

    Active Member

    Oct 21, 2007
    If it were me, theres no way i'd be using equipment there. without a proper ground, a short or other problem can cause metal chassis, grounded stands, mic's, instruments etc to be LIVE. as in i'm holding the mic then zap i'm dead. not good.
  4. SgtWookie


    Jul 17, 2007
    The "rehearsal room" sounds like a death trap. There are multiple problems with the wiring; ie: reversed hot/neutral and no ground. Don't plug your equipment in there again until they get it fixed.