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Electrical Grounding Issues?

Discussion in 'Recording' started by Guitarfreak, Jun 25, 2009.

  1. Guitarfreak

    Guitarfreak Well-Known Member

    The amp I just got secondhand off my friend (actually third hand because he got it from his friend...) has a bit of a problem in the grounding dept. One of the first things I noticed was that the plug didn't have a ground on it. It did, but it was torn off/broken.

    Is this a problem? I have it plugged into a power strip if that makes any difference. If it is a problem, how urgent is it? Should I even play it, or could that cause damage?
     
  2. TheJackAttack

    TheJackAttack Distinguished Member

    Go to Home Despot and buy a plug end. Strip the cord and screw the lines down to their proper terminals. Tighten the strain relief and voila, a proper power cord.

    You shouldn't use it as is. A power strip does not help when the internal wiring of the amp goes goofy. Someone obviously thought they were making their own ground lift. It doesn't really work that way safely.
     
  3. Guitarfreak

    Guitarfreak Well-Known Member

    Now if only I was competent enough to pull that off...

    I could probably get that plug end no problem, the thing I am worried about is doing it lol. Would you say that this is a good step by step guide? http://www.ehow.com/how_117563_fix-electrical-plug.html
     
  4. jg49

    jg49 Well-Known Member

    This is a very simple electrical repair and the guide is more than adequate. If you cut off the cord end and bring it with you when you go to buy the replacement plug you are more likely to get exactly what you need. Just be sure that your connections have no frayed/loose wires that are not completely under the connectors and you have not cut the insulation on any of the wires and you are golden. On a 1 to 10 scale the difficulty of this repair is about a 3.
     
  5. TheJackAttack

    TheJackAttack Distinguished Member

    Black to Brass

    White to Silver

    Green to ground.

    On a polarized plug, the wider blade is neutral (silver screw, white wire).

    No solder necessary.
     
  6. dvdhawk

    dvdhawk Well-Known Member

    The step by step guide you link to is OK, but I wouldn't buy a cheap plug like the one illustrated, that one is more for a lamp or something that doesn't get much wear. For a guitar amp (or anything else that is going to get moved and plugged in and unplugged a lot) I'd buy something heavier with a good strain relief / clamp.

    Although this is a very easy repair for the average DIYer, you have to give electricity the respect it deserves and if you decide to proceed it will be at your own risk. If you are unsure of your ability to follow directions, please have a qualified electrician do this repair. If you start this repair and are unsure of anything, or have a different color code inside the wire, bail out safely and make sure you keep the old plug for the electrician to refer to.

    Once you've gone to the hardware store and bought a suitable new plug, you should be able to do this repair in just a few minutes with a screwdriver, wire cutters. Wire strippers would be useful, but you can use a utility knife IF YOU ARE EXTREMELY CAREFUL.

    Just a few tips if you decide to tackle this yourself:

    Make sure the amp is unplugged from EVERYTHING.

    Cut off the old plug with a nice clean straight cut. If the wire near the plug is severely bent or flexed, don't be afraid to cut a few more inches off to make sure you are working with good, unfrayed wire.

    Disassemble the new plug. Make sure you have the back part of the plug housing slid onto the cable before you start the next steps. It will be easier to do before you separate and strip the 3 conductors - and it's easy to forget once you start prepping the wires - so do it NOW!

    Cut back a little of the wire's outer jacket. But don't remove too much of the cable's outer jacket, you want the jacket to extend inside the plug's housing / clamp / strain relief when assembled. An inch is usually about right - but you may need to cut back a little more or a little less depending on your specific plug.

    Strip the right amount of the color-coded insulation (usually black, white, green) from the inner wires to give you the desired amount of bare wire. A lot of plugs have a strip gauge molded somewhere on them to show you how much insulation to strip off. Use it, so you don't remove too much or too little of the wire's insulation. Excessive bare wire inside anything high-voltage is asking for sparks. Too little bare wire may result in poor contact. Different style plugs will be different and it may take some trial and error until you're happy with your technique.

    Be careful not to nick the remaining insulation on the individual conductors. Give it a close visual inspection in good light while flexing the conductors to expose any bare wire or deep cuts, especially in the area of any cuts you may have made.

    Twist the exposed copper strands of the green wire to keep the smaller strands bunched together with no stray strands sticking out: repeat for the white and black. (in no particular order) Keeping green, white, and black separate of course.

    Prepare all three conductors before you insert them into the lugs. Try to get them all to the exact same length if you can - so one of them doesn't take all the stress if pulled on.

    Follow JackAttack's color coding:

    and you can't go wrong. (some connectors will even say 'white' somewhere by the lugs to help you keep them straight ) Line them up and insert all 3 conductors into their respective lugs at the same time if you can, (and with your third hand) use the screwdriver to gently snug them up - but not real tight yet.

    Inspect it carefully for any stray strands that didn't go into their lugs, if you've got stragglers take them all out, and do it again until it's right.

    When you have each individual strand accounted for, go ahead and tighten each lug. Use a suitably large bladed screwdriver and tighten the lugs as tight as you feel you can without stripping them out.

    Assemble the plug housing and secure the cable clamp/ strain relief.

    Now time for the climax of our little one act play ...... the moment of truth.......

    Take a deep breath .... plug in the amp ......

    No sparks? No popping breakers? No bright light at the end of a long tunnel, leading to a conversation with Edison himself about what you did wrong?

    Good!.... Another life-skill for your musical resume.

    Again in case you missed it:
    Although this is a very easy repair for the average DIYer, you have to give electricity the respect it deserves and if you decide to proceed it will be at your own risk. If you are unsure of your ability to follow directions, please have someone qualified do this repair.


    Good luck.
     
  7. Guitarfreak

    Guitarfreak Well-Known Member

    When you said don't use a crappy connector, did you mean quality housing or something about voltage? Because there was a connector that was rated at 250v, but the guy said that wasn't what I needed. I got this one rated at 120v, do you think it is good enough?

    Photo141.jpg
     
  8. TheJackAttack

    TheJackAttack Distinguished Member

    I can't see the blades very well but this should be ok. DVDHawk wrote a very nice tutorial for you.

    Technically you are looking for a NEMA 5-15R or a 5-20R. Single phase 120V is what your standard US current is at the wall. Your household wall receptacles will be rated at 15 amps and commercial receptacles are rated at 20 amps and should be installed with the ground hole on the bottom. The final amperage will be determined by the breaker to which the receptacle is attached.

    TMI Skip Alert:

    The picture is not one of these but to be thorough (as opposed to Thoreau), stay away from L6-30 or other twist lock plugs unless you are starting to build a large PA system with many amp racks and distribution panel. Most homes and clubs will not have receptacles for these at all.
     
  9. Guitarfreak

    Guitarfreak Well-Known Member

    I did it! Thanks for your help guys I really appreciate it. I had my grandfather help me over Skype for some over the shoulder assistance lol, but other than that you were spot on.
     
  10. TheJackAttack

    TheJackAttack Distinguished Member

    That's what grandfathers are for. That and whippy sticks from the wood shed.
     

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