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Old 23rd Aug 2010, 10:42 am   #10
bluepilot
Heptode
 
Join Date: Feb 2010
Location: Duffort, Gers, France
Posts: 714
Default Re: Old car radio - how to change polarity?

Many years ago, I had an old Morris Minor (+ earth) and a new radio (- earth). The Minor had a hardboard shelf below the dash board which seemed like good enough insulation so I mounted the radio on that. Worked very well. Unfortunately I didn't notice that the shelf had a steel reinforcing bar in it. (I guess it would have been a bit wobbly if it hadn't). Somehow I had managed to miss the bar when I drilled the mounting holes. Then one day whilst transporting a young lady, she knocked her knee against the radio. It moved it enough to short out the mounting bolts and the rod. Result - dead short across the battery, lots of sparks and smoke and young lady disappearing down the road never to be seen again. The moral is, if you're going to insulate the radio from the car, make sure you do it properly. If you can't switch the polarity of car or radio, I would tend to get another radio.
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