Is it plugged in?

 

While you may want to laugh we’ve been on countless service calls and those hour long support calls where the printer wasn’t connected, or the customer forgot to pay their internet bill.  While many technicians forgot the basics we can never forget the standards and basic procedures.  In this section we are going to cover Laptop and Desktop Power guidelines.

 

Laptop Power

Laptop’s can be a bit more difficult to diagnose than Desktops, so we are going to cover both PCs and Intel based Macbooks. While there is a variety of laptops, various electrical connections, batteries etc it’s important to have the tools you need for the job.  We recommend at least 2 good “universal” chargers, a laptop battery charger (external), spare laptop batteries (can be almost dead), iPad charger and Macbook Charger.  This should cover most circumstances.

  1. Visually inspect customer charger for tears, snags, electric tape or any other issues.  When in doubt DO NOT use the clients charger, use a tester you don’t want to start an electrical fire.
    1. You can test a charger with voltmeter, simply set the voltmeter to DC (direct current) and set the negative (black) node to the exterior of the charger and the positive (red) node to the interior pin or casing.  Be very careful not to cross anything and short out the unit.  Look at the adapter to see what the voltage output should be, if you have no voltage or irregular voltage then the charger is most likely bad, continue testing rest of machine if the unit passes with a test charger.
  2. Plug in charger and inspect for lights, does the machine have any lights at all, most will have a charging light indicating power to the board.
    1. Does it power on or make any sounds, blink codes or other flashing indicators?  These can be googled or looked in the manual.
  3. Remove Battery from unit and repeat above
    1. If available use tester battery without charger and test for power on.
  4. Replace with known good tester charger and repeat above. (Note Dells and some manufactures are requiring original OEM chargers to charge and run but generic should be fine for testing)
  5. If the machine still does not power on plug in known good charger remove battery use a voltmeter and find the prongs where the battery plugs into the unit on the bottom.  Place negative terminal on ground (you can usually you a screw or most the time the larger pin on the laptop battery terminal is the ground) and test each pin for voltage.  Each laptop will have a different power voltage, most average around 5.5v DC.  If you get a charge this tells you that the power adapter on the motherboard is not broken and the motherboard or a critical component on the board has failed.  In most cases it’s best to call it a total loss due to the amount of labor and expense in replacing the motherboard and any other components that could be damaged due to power issues.  If you do not get power there is a good possibility that the DC jack on the motherboard has been damaged, on many units the grounding pin has been broken or damaged.   Depending on the unit some may have a detachable power board that is separate from the motherboard and can simply be replaced, on other units it requires de-soldering of the DC jack and replacement with a new DC jack.  This requires speciality desolder equipment and a good knowledge of basic electronics.  Some individuals feel comfortable performing this type of repair, but depending on how the unit was broken and if the customer had been twisting or turning the power plug it could have caused a short in the board and caused permanent damage and replacing the DC jack will not resolve the issue as the unit has already been shorted.  It’s a risk replacing either way.  We have a very high success rate but have stopped offering it as a service to our customers due to the amount of work involved, however for high end units or personal units I will still perform the repair.  Information will be provided at the end of this manual to provide further training and equipment recommended for performing this type of repair.

 

Desktop Power

While most technicians would think desktops should be simpler to diagnose they can actually take a bit more time due to the amount of variables some desktops have.

 

Standard Desktop

  1. Attempt to turn on power to the unit with tester power cord
  2. Look for any lights on board, or tower
    1. Lights on the board with no power after testing can indicate bad motherboard or CPU or both.
  3. Remove case and use power supply tester or voltmeter to test power supply
  4. If still no power replace with known good power supply
  5. Remove memory an attempt to boot, machine should beep if it’s getting to POST
  6. Remove all ancillary cards, extra video cards, sata cards etc.
  7. Unplug all devices, USB, SATA, IDE
  8. Remove cmos battery if possible
  9. Jumper the power switch on bios if possible

 

iMac Power / All in One Units

These units can be much more difficult to diagnose.  On older G5 iMacs there is a series of LEDs on the board that can help provide power indication (http://support.apple.com/kb/HT2831).  On intel models and other all in one units you first need to determine whether or not the AC inverter is built in with a Mini-itx or speciality power supply or if it’s similar to a laptop where the power conversion is done in the power adapter.  This should be fairly easy to identify just via a visual inspection.

Article by Bizanator

I'm a security researcher, pentester and general IT guru professionally since 2003. While IT and security has been a habit of mine, literally learning my ABCs on an Apple IIe I have worked on virtually every operating system in the past 25 years. Learning about memory manipulation starting in the early Blizzard days I found an affinity in security and exploit development. My career has allowed me to work in a variety of industries and have been a strong supporter of open source and virtualization. My goal here is to provide a forum of information where when you're brain dead hopefully myself or one of our members can work together in the spirit of open source and resolving those brain dead moments. You can request a consultation with me on Maven.

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