I bought a Seagate USB harddrive in a case. It was on the bargain shelf because it was missing the power supply module (transformer). The plug is labelled 12VDC 2.0 A.
I have lots of these transformer modules since I bought a whole box of them at an auction, and I have several 12VDC ones. One is a 4A, the others are smaller. I'd almost expect the 1.5A ones that I have to work also, because I know that harddrives do not use that much power.
Either way, the problem is the polarity. It has one of those common center pin and side connectors that look like a target in a hole. I know these are normally wired so the center pin is positive, bu there are exceptions. I can easily measure the polarity of the module output with my meter, but how can I measure the input of the harddrive to determine which polarity is required?
Originally I intended to open it and look at the circuit board for polarity markings, but they have it sealed with some sort of oddball screws that look like a star with a pin in the middle. I've considered drilling them out, if I can use a meter to determine the polarity, that should be fine.
Anyone know how?