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Positive Earth - an explanation please
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norustplease



Joined: 11 Apr 2011
Posts: 779
Location: Lancashire

PostPosted: Mon Jun 20, 2016 11:22 am    Post subject: Reply with quote

pigtin's account matches my own recollections and understandings of the reasons for a change to negative earth.
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jp928



Joined: 07 Jun 2016
Posts: 249
Location: Australia

PostPosted: Mon Jun 27, 2016 2:34 am    Post subject: Reply with quote

Solid state devices rely on natural characteristics of things like silicon to work. Larger diodes etc are easier to make when the body is on the -ve side for mounting and heat dissipation reasons. To mount such parts on a +ve earth chassis would require insulation, which would reduce heat dissipation.
In my memory most cars went to neg earth around the time alternators and transistor radios became common - alternators became necessary as electrical loads increased significantly, and generators became unable to meet demand - they wont stand higher rpm.
jp
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1735
Location: Above the snow line in old Monmouthshire

PostPosted: Mon Jun 27, 2016 7:45 pm    Post subject: Reply with quote

jp928 wrote:
Solid state devices rely on natural characteristics of things like silicon to work. Larger diodes etc are easier to make when the body is on the -ve side for mounting and heat dissipation reasons. To mount such parts on a +ve earth chassis would require insulation, which would reduce heat dissipation.
In my memory most cars went to neg earth around the time alternators and transistor radios became common - alternators became necessary as electrical loads increased significantly, and generators became unable to meet demand - they wont stand higher rpm.
jp


Right, that makes sense. Thanks for clearing that one up Smile
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