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Post subject: Save my life and my amp
Posted: Sat Aug 26, 2017 9:43 am
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:( Ok so i got a fender mustang 1 (v2) from my friend. I brought it home and plugged it in everything works as it should no problems. But then while switching it on again i accidentally touched a screw and got an electric shock for a second. So i used an electric tester and found out that all the nuts on top have voltage(tester showed positive). Now what can be the problem because I don't want to take it to a GOOD trusted tech who's more than 1 hour away. I can open it up and see if someone guides me. I have some experience with projects so i think i can do it. But i need some guidance.
ALSO: i tested with the switch on amp turned off and there is still voltage in the screws. Save my life lol.


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Post subject: Re: Save my life and my amp
Posted: Wed Aug 30, 2017 8:31 pm
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Ronhudson wrote:
:( Ok so i got a fender mustang 1 (v2) from my friend. I brought it home and plugged it in everything works as it should no problems. But then while switching it on again i accidentally touched a screw and got an electric shock for a second. So i used an electric tester and found out that all the nuts on top have voltage(tester showed positive). Now what can be the problem because I don't want to take it to a GOOD trusted tech who's more than 1 hour away. I can open it up and see if someone guides me. I have some experience with projects so i think i can do it. But i need some guidance.
ALSO: i tested with the switch on amp turned off and there is still voltage in the screws. Save my life lol.


I'd certainly start by plugging it into a different outlet! And try a different IEC power cord. Normally, any fault that would put the full line voltage on the chassis should blow the fuse.

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Post subject: Re: Save my life and my amp
Posted: Thu Aug 31, 2017 6:13 am
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All current amp designs connect the chassis directly to the AC plug ground wire (3rd prong) of the AC plug. The amp will operate without being grounded but as you found out, it'll shock you. Sounds like you're reading voltage because the amp isn't grounded. Check that the AC wire you're using and that it's firmly inserted in the back of the amp and if you still read voltage then check the AC power connection ground. There's many possible reasons the ground connection is floating. You might be using an extension cord, power strip, or AC plug adaptor that's not connecting the amp to ground. If anything AC powerwise is two wire that won't ground the amp. Then there's the common possibility that the power outlet wasn't wired with a ground even if it has a three prong socket (lots of ways this could occur). If you're comfortable with measuring AC with the meter you should be able to confirm if the ground connection is wired and the third prong of the amp AC plug is properly connected to the house ground. Good luck and get this solved.


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Post subject: Re: Save my life and my amp
Posted: Fri Sep 01, 2017 12:25 am
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MYREL Tech wrote:
All current amp designs connect the chassis directly to the AC plug ground wire (3rd prong) of the AC plug. The amp will operate without being grounded but as you found out, it'll shock you. Sounds like you're reading voltage because the amp isn't grounded. Check that the AC wire you're using and that it's firmly inserted in the back of the amp and if you still read voltage then check the AC power connection ground. There's many possible reasons the ground connection is floating. You might be using an extension cord, power strip, or AC plug adaptor that's not connecting the amp to ground. If anything AC powerwise is two wire that won't ground the amp. Then there's the common possibility that the power outlet wasn't wired with a ground even if it has a three prong socket (lots of ways this could occur). If you're comfortable with measuring AC with the meter you should be able to confirm if the ground connection is wired and the third prong of the amp AC plug is properly connected to the house ground. Good luck and get this solved.

I have the three prong cable. I tried it in different outlets at my home and also at my friend's home. Still getting that voltage. For now i stuck some electrical insulation on the screws. But I'm afraid if that's some big issue and can send some voltage into the guitar too(lol). Sorry if I'm being a douche :D


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Post subject: Re: Save my life and my amp
Posted: Thu Sep 07, 2017 12:32 pm
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Unplug the Power cord and use your Ohm-meter to check the 3rd prong ground connection to the screws you're getting a voltage reading from. See if they're all connected to Chassis ground. Also, what exactly are you reading AC volts, DC volts, and how many volts. Just to be sure, swap the power cord with a different one and see what you read. If there's no connection from that 3rd prong to the amp screws then it might be a loose internal connection right at the amp power plug socket. Then you've got to have a Tech check it. Rarely is it an internal thing but it's possible.


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