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Old 4th November 2007, 09:13 PM   #1
jcspurs is offline jcspurs  United Kingdom
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Default problem with polytone amp

Hi this is my first post and im not that technically minded so bear with me please, Im a professional guitarist and ive had a polytone minibrute for almost 20 years from new no problems. yesterday i was doing a gig and as soon as i turned it on it tripped the fuse in the venue and lights went off etc. i took the amp home and it was fine. i took it to another venue today and it tripped the fuse again i took it home and it works fine. i cant understand it. the only thing ive had done is someone opened the plug and wired the plug again could that be the reason. any help would be greatly appreciated thx jules
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Old 4th November 2007, 10:31 PM   #2
djk is offline djk
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Someone could have swapped the hot and neutral when they re-wired the plug.

Many homes have ungrounded outlets, so the problem wouldn't show up until you went to the clubs and plugged in to a real grounded outlet.

Buy an outlet tester and check the wiring at home and everwhere you go before you plug in. Mine cost me $6.
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Old 5th November 2007, 10:42 AM   #3
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Short to ground? Like djk says, if you have ungrounded outlets at home you wouldn't notice.

But this shouldn't happen if active and neutral are swapped as these should be isolated from chassis and ground.

Or, does electrical safety standards in the US allow neutral connected to the case in the equipment? If so, then the regulations are insanely stupid and dangerous. Over here some kilovolts of insulation is required even between neutral and case!
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Old 5th November 2007, 02:46 PM   #4
jcspurs is offline jcspurs  United Kingdom
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thanks guys thats really helpful . that must be it. ive just had a look inside and hes put the green wire in neutral, thewhite in earth and the black in live. is that wrong? as i said the amps 20years old this looks like old wiring. any help out there??
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Old 5th November 2007, 03:03 PM   #5
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The commercial premises that you tried your amp at probably have RCD protection on the circuits, which your home might not have. So if the amp was using the earth as the neutral, the RCD would trip out.
Green/Yellow is earth
Black is live
White is neutral

And for you guys not in the UK, every household over here has earthed outlets.
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Old 5th November 2007, 03:21 PM   #6
celt is offline celt  United States
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Quote:
Originally posted by ben12345
And for you guys not in the UK, every household over here has earthed outlets.

Wish ours did. Have seen many houses built since the 70's that have three prong outlets with no ground system wired in.
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Old 5th November 2007, 08:19 PM   #7
djk is offline djk
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If it is a black-white-green color scheme then black is hot, white is neutral, and green is ground (sounds like yours is wired wrong).
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Old 5th November 2007, 10:53 PM   #8
jcspurs is offline jcspurs  United Kingdom
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thanks chaps i owe you guys a pint i hope thats fixed the problem i was going to pay a guy 50 quid to fix it cheers jules check out my website if you get a chance www.londonjazztrio.com
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Old 6th November 2007, 12:06 PM   #9
jaycee is offline jaycee  United Kingdom
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I guess this amp was probably imported from the States or so.. black-white-green is a US thing and has never been used in the UK (it used to be red-black-green here).

It might be worth having someone replace the cord with some UK coded flex, or perhaps fit an IEC (kettle plug) connector to the back of the unit.
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