How To Change Your Computers Clock Battery
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Changing out a battery is not difficult on most Mac systems. Simply pry off the retainer and pull the battery out. Reverse the procedure with the new battery making sure the + is positioned correctly.
Restart your system and reset the date and time and other control panel settings as needed.
Note for the 4.5V Batteries, they are small square and black. They are stuck down with velcro. Simply pull up the old battery and unhook the cable. Reverse the procedure. There is only one way the cable plugs back in.
Once you've replaced the battery, you will want to reset several settings. If you're on a network, you'll want to open the Chooser and enable AppleTalk. Note some Macs may not support all these control panels (preferences in OSX). These are the control panels you'll need to use:
Startup Disk. Always reset your startup disk. Your system may not boot well or give you the flashing question mark if it gets confused.
Date & Time. First, choose your time zone, then set the date and time.
Memory - Mac OS 8.5 and later will usually set this automatically. Set your cache to a Meg if you have plenty and 1 meg over on virtual.
Network or AppleTalk. If you're on a network that isn't LocalTalk, you will need to reset your network connection on any Mac with a LocalTalk port.
Mouse and Keyboard.
You'll need to reset the mouse tracking and double-click speeds, as well as setting the keyboard delay and repeat.
Energy Saver or Auto On/Off. Energy saving settings, power-up time, etc. are stored in PRAM and need to be reset.
Monitors and Sound or Monitors & Sound. You need to reset speaker volume and monitor bit-depth and possibly resolution.