wrong polarity?

[tuggerv8]

i've just bought a small amplifier for my classic car from ebay. the power plug would fit either correctly or wrong thus putting 12 volts into the ground lead. how can i fix this? is it just change a resistor or more complicated? i need to take it apart so i'll be able to post a picture of the board soon, but some assistance would be great please, mark

 

[Reloadron]

Hi Mark

This is one of those things where a picture or two is worth a thousand words. I can tell you if it is a matter of polarity on a plug I don't see a resistor as a solution. A few pictures well narated and I am sure this can be resolved for you.

Ron

 

[tuggerv8]

thanks buddy. i'll get to stripping it asap

 

[crutschow]

If the amp can tolerate a diode voltage drop (≈0.7V for a standard diode, ≈0.5V for a Schottky diode), then a diode in series with one of the power leads with prevent any damage from reverse polarity being applied.

 

[tuggerv8]

i opened it up and immediatly saw the problem. there is a spare eathing wire that when earthed it made the unit work! a quick bit of solder and i'll be cruising again.
thanks for your help and prompt responces, mark