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Mac Forum / General / Hardware / May 2006Need to know polarity of RAYOVAC 4.5V battery (840,841)
Hi everyone, I was testing my 4.5V RayOVac battery and I pulled the keyed 4-pin connector off the wires to test it and forgot to check which way the connector is keyed before I did. Darn it! Now I don't know which way to put the wires back into the connector plug. This is for the Tanzania MB but the MB header doesn't indicate polarity. Of course normally that wouldn't matter since the connector plug is keyed. It's either: RED Positive (+) KEY OPEN BLACK Negative (-) or BLACK Negative (-) KEY OPEN RED Positive (+) I can always buy a new battery to find out but if anyone here knows I would appreciate it. Thanks. > I can always buy a new battery to find out but if anyone here knows I > would appreciate it. Thanks. Or for about $10 bucks a meter at Radio Shack. > > I can always buy a new battery to find out but if anyone here knows I > > would appreciate it. Thanks. > > Or for about $10 bucks a meter at Radio Shack. How is a meter going to show me the polarity of the MB header? >> > I can always buy a new battery to find out but if anyone here knows I >> > would appreciate it. Thanks. >> >> Or for about $10 bucks a meter at Radio Shack. > > How is a meter going to show me the polarity of the MB header? But if the connector is keyed, then that means it will only go in one way. Is that the case? If so, then the color coding is likely good, and read is positive and black is ground. Maybe it's a wrong guess, but I'd treat it as pretty certain that negative goes to ground. For a RAM backup, that seems a pretty safe assumption (other applications, it might not be). Hence, you can find a known ground point, if nothing else where the power supply ground hits the motherboard, and then use the ohmmeter function of the meter to determine which of the leads on the connector goes to that ground point. That's negative, and then the other lead would be positive. Other things that would be an indicator is if an electrolytic capacitor is connected across the battery. Those are polarized, and hence whichever lead goes to the lead on the capacitor that is marked "+" is where the plus side of the battery goes. Are you sure there's no not-easily-readable marking on the connector, or on the motherboard itself? Michael > >> > I can always buy a new battery to find out but if anyone here knows I > >> > would appreciate it. Thanks. [quoted text clipped - 23 lines] > Are you sure there's no not-easily-readable marking on the connector, > or on the motherboard itself? There is no marking on the MB or the connector. The polarity of the battery is known. What is unknown is the polarity of the MB header. |
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