speed reduction cable

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Fraser
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speed reduction cable

Post by Fraser » Sun Dec 12, 2010 6:09 pm

I was wondering if any electronics people had any opinion on this speed reduction cable. It seems to connect power to 12V and ground to 5V to effectively have 7V power. I was looking at one in a shop and it must have been made wrong because the power was connected to 5V and ground to 12V. I could probably make something suitable if you think the idea is not dodgy.

http://www.maplin.co.uk/Module.aspx?ModuleNo=37054

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retroclinic
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Re: speed reduction cable

Post by retroclinic » Sun Dec 12, 2010 7:02 pm

That's fine, they've just connected as you say the ground to 5v and the positive to 12v, so it gives effectivly 7v differential between the supplies. As long as you don't have a metal fan that earths to the case! Wiring the positive to 5v and ground to 12v may cause a smokie bang bang unless it's a clever fan and is protected from reverse, or a mechanical one that will run backwards.

Mark.

PS. Don't rely on the wiring colour to tell 5 from 12. Look inside a Sega arcade cabinet, and 5v is yellow, with 12v as red...which doesn't really pose a problem until you start to MAME a cabinet with a PC and forget......
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AndyF
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Re: speed reduction cable

Post by AndyF » Sun Dec 12, 2010 8:13 pm

retroclinic wrote: PS. Don't rely on the wiring colour to tell 5 from 12. Look inside a Sega arcade cabinet, and 5v is yellow, with 12v as red...which doesn't really pose a problem until you start to MAME a cabinet with a PC and forget......
If memory serves correctly, on the Amstrad CPC, Spectrum +3 (and possibly the PCW thing) the built in 3" ( yes, 3 not 3.5 :( ) disc drive has the wiring the other way around too, if you attempt to retrofit a 3.5 it will be 'unhappy' :mrgreen: due to 5v and 12v being swapped :oops: , can't remember the colours off hand either although they are not the usual ones.
Andy

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