One of the scariest things that can happen to your Mac is a failure to turn on at all. You press the power button and nothing happens - no startup sound, no light, nothing. If this happens, you can check several things before hauling your Mac to the nearest Apple Store for repair.
First, trace the entire flow of electricity to your Mac. Check your Mac's power cord to ensure it is firmly seated where it connects to the computer as well as where it plugs into the wall. If it goes through an outlet strip or a UPS, make sure that's also connected and turned on. Also check that any surge protectors are still working - a power surge might have knocked them off. You can confirm that an outlet is good by plugging in something else, such as a light. If the outlet and all cable connections check out, make sure the power cord has no crimps, breaks, or other damage.
Once you've established that your AC power path is good, it's time to look at your Mac itself. Unplug everything you can - not the power cord, your mouse and keyboard if they're wired, and your monitor if it's not built in - but disconnect everything else and try pressing the power button again. If your Mac turns on, you know that one of your peripherals was at fault.
If your Mac doesn't turn on, it's worth trying to reset your Mac's SMC (System Management Controller), a chip that manages a number of hardware functions - including the operation of the power button. Directions vary by Mac model; see Apple's instructions for details (http://support.apple.com/kb/ht3964).
If you have a Mac laptop, its battery should last through most power outages, so you may not notice that you have a power-related problem until the battery runs out, at which point your Mac might simply appear to be dead. So try all the above tips, but also check your power adapter. If you have an AC cable attached to the adapter (as opposed to a plug going directly into the wall), make sure that cable is securely connected. If you have access to another AC adapter, switch to it briefly - that will tell you whether the original adapter is bad or whether it's something in your Mac itself.
Still no luck? In that case, it's time for professional help. An Apple Store or authorized repair center should be able to diagnose and fix the problem.
Did you know that you can quickly access information about your router, and check if your network is performing well? See your BSSID, signal-to-noise ratio, and even the transmit rate between your router and computer. All it takes is a press of a button and a click of your trackpad/mouse.
If you hold down the Option (alt) key and click the Wi-Fi icon in the menu bar, it will provide you with details about your router and the network you're using. The items in gray (except for "Wi-Fi: On") are all pieces of additional information seen only in this mode.
• IP Address: This is your computer's IP address.
• Router: Your router's IP address. You can type this into your browser to access your router's web interface.
• Internet: This tells you if you are able to access the internet or not. If not, open Wireless Diagnostics.
• Security: Your router's security. Most routers on the market offer WPA2 Personal, and it keeps your network encrypted.
• BSSID: This is your router's MAC, or hardware address. It acts as an identifier for your router that lets it talk to other network-connected devices.
• Channel: This is your WLAN channel, and it determines which radio frequency the router uses to transmit information.
• RSSI: Received Signal Strength Indicator measures how well a device "hears" a signal from the router. It's useful for determining if you have enough signal to get a good wireless connection.
• Noise: This measures how much radio noise is interfering with the RSSI signal. Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels.
• TX Rate: The transmit rate is the speed of the data that is transmitted between your router and your computer. Right now I have a speed of 450 Mbps.
• PHY Mode: This is the wireless protocol that the router uses, according to the IEEE 802.11 wireless standard.
• MCS Index: This number corresponds to the protocols uses to encode the radio signal.
If you're having printing issues, there are lots of troubleshooting steps to try. You should check the printer's network connection and perhaps search for any new drivers your model has available. Another good idea is turning the device off and on again to see if the problem's just an intermittent one. You could even delete the printer from System Preferences > Printers & Scanners and reconfigure it.
There is, however, a troubleshooting step that you can attempt if nothing else seems to work - resetting your entire printing system.
This can be especially helpful if you're pretty certain that your Mac's the problem, not the printer (if your other computers can print just fine). You'll want to use this only as a last resort, though, because you'll have to set up all of your printers and scanners again.
Here's how you do it:
• Open System Preferences from the Apple menu and click "Printers & Scanners"
• Right or Control click on the white box on the left of the tab (where your devices are listed)
• Choose "Reset printing system..." and click OK
• Wait for your Mac to complete the task (which can take a little while) and after it's finished, select the plus (+) button on the "Printers & Scanners" window to walk through adding your devices back in
Is Safari no longer remembering logins and passwords? Is Mail.app asking for a password every time you launch the app and try to check or send mail, despite the fact that you’ve entered login credentials over and over? When a Mac app no longer remembers password and login data, it’s often the result of corrupted keychain files. This is easy to fix in three easy steps with Keychain Access first aid.
• Launch Keychain Access located in /Applications/Utilities
• Open the "Keychain Access" menu and choose "Keychain First Aid"
• Enter the user’s password and check the "Repair" box, then click "Start"
After keychain repairs are completed, exit out of Keychain Access and return to the application that wasn't remembering the login and password information. You may be asked one more time for the login, but from this point on it should remember it.
Your Mac stores certain settings in a special memory area even if it is turned off. On Intel-based Macs, this is stored in memory known as NVRAM, on PowerPC-based Macs, this is stored in memory known as PRAM. Information stored in NVRAM or PRAM may include speaker volume, screen resolution and startup disk selection. You may need to reset the NVRAM or PRAM if you experience issues related to these functions.
For example, if your Mac starts up from a startup disk other than the one you've specified in Startup Disk preferences, or if a "question mark" icon appears briefly when your Mac starts up, resetting NVRAM or PRAM may help.
• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option (Alt), P and R.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys (you must press this key combination before the gray screen appears).
• Hold the keys down until the computer restarts and you hear the startup sound for the second time, then release the keys.
After resetting NVRAM or PRAM you may need to reconfigure your settings for speaker volume, screen resolution, startup disk selection, time zone information. If issues persist, your Mac's logic board battery (not a portable Mac's rechargeable battery) may need to be replaced. The logic board battery helps retain NVRAM/PRAM settings when your computer is shut down. You can take your Mac to a Mac Genius or Apple Authorized Service Provider to replace the battery on the logic board.
In some situations, you may need to reset your computer's System Management Controller (SMC). Learn how to identify these conditions and reset the SMC.