I am trying to fix and expensive alarm clock where the wire has snapped from the jack plug. Now if I know the pos and neg coming out of the mains how do i determine the neg and pos of the jack? One wire is centred and one goes to the side. Is centre neg a std convention? on a jack plug? I’ve cut the housing back as far as I can.with total removing the hard plstic casing of the jack.I hope tye jack plug description is adequate. It is like the lumicycle plugs the are on the battery and plug into the lights.

cheers

Look where the plug goes in. There is often a little info imprint/sticker telling you the voltage and the polarity.

nope.doesn’t say

It is most likely to be centre positive I think, but you really need to know for sure. Like Graham says, look on the power adapter for voltage / polarity (or maybe on a sticker on the clock itself). If the wires are two colours, voltmeter on them to find out which one is positive, then look at where they go into the plug, and use the continuity checker on the voltmeter to find out which one goes to the centre.

Once you’ve found out the details, easiest thing to do is just go to maplin and buy one of the right voltage, and make sure you set the polarity correctly. Easier than soldering the wires back, and cheapish. Although if you’re okay at soldering and have soldering kit handy, and a voltmeter to find which wire is which, you could fix it pretty quick.

By the way – probably just how you’re wording it, but you are just fixing the wires between the power adapter and the clock, not doing anything with mains power / wiring your own plug on right?

Joe

ok thanks all. Will look into it all a bit later. cheers

More than likely centre positive unless its a lumicycle alarm clock! But there really should be a moulded symbol next the jack point on the clock. showing you the polarity of the jack. It is also likely to be a 2.5mm DC power connector.

cheers smudge. BTW loving the batteries.