How to test a motherboard with a multimeter

A motherboard takes care of all the major functions of a computer and holds together the most important components like the CPU, memory, hard drives, expansion slots, and connectors. It also determines the features and functions your office computers can have, making it essential for the overall productivity of your business.

Frequent testing of a motherboard is necessary for its upkeep. A digital multimeter, like those at RS Components, is the perfect tool for testing a motherboard.

Find out how to safely and effectively use a multimeter to test a motherboard.

Follow these steps to test a motherboard with a digital multimeter for DC voltages

  1. Switch on your computer and plug in the 20-pin ATX connector into it.
  2. Set the multimeter reading to 20V.
  3. Take the black negative probe of the multimeter and make contact on the pins 15, 16 and 17 of the 20-pin ATX connector. 
  4. Take the red positive probe of the multimeter and make contact on the pins 9 and 14. Pin 9 should read 5V and pin 14 should read a value between 3V and 5V. Any other reading indicates a problem in the circuit.
  5. Switch the PC on and see whether the reading drops to zero. If not, there is a fault with the circuit.
  6. Now, take the red positive probe of the multimeter again and make contact on pin 8. If the reading on the multimeter shows more than 2.5V, reset the computer. If the reading goes down to zero and then goes back up, there are no issues with the computer. If not, the motherboard has an issue.

 Follow these steps to test a motherboard with a digital multimeter for short circuits

  1. Switch off your computer and unplug it. Wait for a few minutes. This is to let the computer cool off and allow the residual charge to drain. 
  2. Set the digital multimeter to the lowest setting, i.e. 200 Ohm.
  3. Now bring the multimeter reading to zero by touching the negative and positive probes together.  Next, touch the probes on the metal chassis of the computer and check the multimeter reading. The reading should still be zero.
  4. Open your computer and carefully remove the 20-pin ATX connector from the motherboard. Connect the red probe to the PSU’s AC ground pin while keeping the black probe on the metal chassis. Bear in mind to keep the black wire pins on the DC connector. During all these instances, all the readings should be pointing to zero.
  5. With the black probe still on the metal chassis, take the red probe and check all the coloured wires. The reading on the digital multimeter should be ideally 50 Ohm or more. A reading less than 50 Ohm means there is a short circuit.
  6. Now, remove the motherboard from the system. Use the red probe to test each of the ground pins. The pins 3, 5, 7, 13, 15, 16 and 17 should show a reading of zero. Any other reading means there is a problem.

Digital multimeters are standard diagnostic tools that have a wide-ranging role in the electronic and electrical industries as they can measure circuit parameters like voltage, current and resistance.

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