ComputerSpaceFan Posted June 28, 2019 Share Posted June 28, 2019 Just picked up a Grandstand Firefox F7 tabletop and it works great but instead of batteries I'd like to plug it into the wall. Only problem is the instructions say to use the Grandstand Mains Power Adapter and to flick the switch on the back of it to negative. Their quote is "Set polarity switch to negative polarity" Can't get an official Grandstand Mains Power Adapter but the good news is I have a Universal Adapter ... now my only problem is what should the pin configuration be? Center positive or center negative. Anyone know? Quote Link to comment Share on other sites More sharing options...
CatPix Posted June 29, 2019 Share Posted June 29, 2019 Do you have a picture of the electricity input on the machine? or instructions maybe? On those older systems the center is usually negative but you never know. Most of the time you can try reversing polarities, but some cheap electronics doesn't like it. Quote Link to comment Share on other sites More sharing options...
NasaManf Posted June 29, 2019 Share Posted June 29, 2019 Talk to an electrician or electronic gadgets service center which might solve your problem. Quote Link to comment Share on other sites More sharing options...
DragonGrafx-16 Posted June 29, 2019 Share Posted June 29, 2019 I think negative polarity is the same as center negative. Usually electronics will show the polarity and the volt and amp specs of the unit near the power jack. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted June 29, 2019 Share Posted June 29, 2019 Not that this helps much, but when I have something like this I want to run off an adapter and don't know the polarity for it, I will take it apart and find out which part of the power jack is attached to ground on the rest of the electronics. Because ground is going to be the negative... Also I've found that a lot of these old tabletops are able to handle some reversed polarity because putting in the batteries backwards didn't usually kill them and the batteries are putting out nearly the same voltage required for the unit to work. In fact... I wonder if the negative terminal of the battery compartment that is actually attached to a wire going into the game would also be tied to the ground or negative off the power jack as well? Hmm.... Quote Link to comment Share on other sites More sharing options...
ComputerSpaceFan Posted July 9, 2019 Author Share Posted July 9, 2019 no worries, I saw some power supplies for sale on eBay and they all say center should be negative EU AC/DC 9V 1A Switching Power Supply adapter, negative polarity inside Quote Link to comment Share on other sites More sharing options...
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