Checking polarity of Power adaptors

Have mislaid the power adaptor for some computer speakers. Have found one same voltage (9v) but unsure of polarity. I need one that is - in centre and + on outside, but the adaptor I have only has a symbol which is a square within a square ... what does that mean? ?

geek_kcc55a, Feb 13, 9:59 am

Means its double insulated and does not need an earth. Nothing to do with the voltage side of things. You're best bet is to test it with a multi meter, red to centre and black to outside you will see a voltage, but if there is a minus symbol that shows up on the screen then its centre neg. They are about $10 from Dick Smith and always handy to have around the place for little jobs like that.

geek_pyro_sniper2002, Feb 13, 10:02 am

You need to know what amp the current requires also, not just the voltage or you may damage them.

geek_babcorp, Feb 13, 10:50 am

Amp side was OK.

geek_kcc55a, Feb 13, 11:01 am