Though it seems a highly technical task, you do not necessarily have to get to a professional technician every time there is a need to test your PC’s glitchy motherboard. If you have a multimeter at home and, of course, a bit of understanding of electronics, you can easily test and try troubleshooting the motherboard by yourself.
However, the most important thing of all is nevertheless to know what type of mainboard faults can be audited and troubleshot at home? Plus, what components to review and which ones to avoid tingling, as there are no complicated wiring schemes therein? And finally, what’s the basic flowchart on how to test a motherboard with a multimeter on your own.
So let’s find the answer to all this in detail below.
How to Test a Motherboard with a Multimeter?
There’s of course only one reason why you’d ever need to open up and test your laptop or PC’s motherboard i.e. your system got completely dumb without any warning. And there are usually two major reasons for this: it can either be due to the mainboard’s voltage/power disruption or because of some sort of short circuitry therein.
That said, you may always need to test your motherboard with a multimeter for these two specific issues only. So let’s check out how it’s done.
#1. How to Test for DC Voltage Issues?
To probe the DC voltages, you’d need to first put the 20-pin ATX connector into its respective socket in the motherboard and make sure the system is plugged into AC. Then set the multimeter’s knob to read 20V DC.
Now, the first step is to take the Black probe of the multimeter and check out the backside of the connector for all the black/GND wires. Usually, pins 15, 16, and 17 take the black wires. So put the multimeter’s Black probe into one of the GND pins (15, 16, or 17).
Then take the Red probe of the multimeter and follow:
- Touch it with Pin 9 (Purple, VSB) which should give you a 5V reading on the meter’s display. If you get 5V, proceed to the next step. If you don’t get 5V, it means there’s either a problem with the PSU or some short circuit in the board, etc.
- Check Pin 14 (Green, PS_On) with the Red probe and it should read somewhere between 3 to 5 Volts.
If it reads 0V but the previous (Purple/VSB) reading was correct (i.e. 5V), try disconnecting the system’s power switch from the board. If you do so and the voltage value (3~5) comes up, it means the power switch is malfunctioning. So fix it.
- Press the power switch to turn the system ON and see if the Green/PS_On voltage drops down to 0V. If no, again it’s highly likely an issue with the switch – probably a bad switch. Try shorting the power switch with a jumper wire, etc. to see if it works. If the reading still doesn’t fall to ~0V, there’s an issue with the CPU.
- With the Green/PS_On reading already at 0V, touch the Red probe to Pin 8 (Gray, Power_OK). It should ideally read somewhere above 2.5V on the meter’s display.
- If it doesn’t read around 2.5V, press the reset button (or short the reset button pins) and see if the Green/PS_On reading drops down to 0V and goes back up to 2.5V or higher again. If yes, you may be better off getting a new more powerful PSU as the existing one is not capable to carry all the load. If the reading doesn’t change after pricking the reset button even, you need to seek a professional technician’s help.
- If the Gray/Power_OK reads correct (i.e. above 2.5V), check out the voltage reading of other wires in the 20-pin connector which should read as:
- Connecting the Red probe to pins 1, 2, and 11 (i.e. Orange wires) should give you a +3.3V reading in the multimeter.
- Red wires i.e. pin 4, 6, 19, and 20 should give +5V.
- The yellow wire (mostly pin 10) should give +12V.
- Whereas pin 12 and pin 18 (Blue and White wires respectively) should give -12V and -5V respectively.
And that’s it. If every wire reads exactly as above, there is no issue with your motherboard’s DC voltages. The Red and Yellow wires in the 20-pin connector may at times show nominal voltages if AC is live and the system powered off.
#2. How to Test a Motherboard with a Multimeter for Short/Open Circuits?
Another possible issue why maybe your system is fully brick is due to some sort of short circuit on the motherboard. And it usually happens when the system is hit by the overrun of electricity. So here’s how to do this test.
- Take your PC off the AC and wait a minute or so to let all the residual (static) electricity flow away.
- Set the multimeter’s knob to the lowest Ohm reading – probably 200 Ohm. And touch both the Red and Black probe with each other to get Zero (0) on the multimeter’s display. Besides that, put both the probes on a bare metallic surface of the chassis to be sure that the meter still reads Zero.
- Now disconnect the 20-pin ATX connector from the motherboard.
- After that, put the Black probe again anywhere on the bare metal of the chassis and check out the PSU’s AC ground pin and the DC connector’s black wire pins with the Red probe. Readings at this stage should also be Zero (0) overall.
- Now again keep one (the Black) probe on the chassis and using the Red probe, check all the DC connector’s non-black wires. All the colored (mostly red) wires should give you a reading of above 50. If any red wire gives out anything below 50, you need a professional’s assistance.
To Test in a More Detailed Way (for Open Circuit Worries)
You can go further in case you want to have one at-length examination for short/open circuit worries. And for that, you’d need to remove the CPU completely from the mainboard socket and then refer to the 20-pin ATX connector’s pinout chart to get an understanding of the board’s connector socket.
Then only test the GND pins on the motherboard connector by keeping the Black probe connected to the bare metal of the chassis (mostly on the screw/mounting holes, etc.). Pins 3, 5, 7, 13, 15, 16, 17 should give you a Zero (0) reading here too.
If you get a value other than zero, you’ve got some sort of problem either in the ATX connector or somewhere else on the board. Try seeking a professional’s assistance in this regard.
How can I test if my motherboard is bad?
The first and foremost indication of a bad or faulty motherboard is a distinctive “BEEP” sound which is heard when you boot up your Laptop/Desktop.
Why would a motherboard stop work?
A motherboard is the most critical component in a laptop or a desktop which holds plenty of sensitive circuitry which could be damaged by improper ventilation leading to thermal issues or poor voltage that could possibly fry it.
Opening up and testing the motherboard at home although seems to be an impossible task, it’s actually not so. All you need to do in such a scenario is to have one multimeter at home, a basic understanding of volts, ohms, etc., and only this article laid open in front of you on another screen. If you have all this, there’s no chance you’ll ever feel reluctant kicking and pulling off this job.
Nevertheless, there’s one thing I’d like you to know: For laptops, the first thing before undertaking a motherboard test is to test its power adapter. Who knows the actual reason for the laptop not coming live might be the charger that’s failing to ship the needed power.
- So first, connect the charger to AC and set the multimeter’s knob to 20V DC rove.
- Then connect the red probe of the multimeter to the connector tip/pin (inside the DC barrel) of the charger and put the black probe on the barrel’s (metallic) body.
- If you get 19V on the meter’s display, you can safely assume that the charger is fine. If not, the charger is faulty and you may need to replace it.
Plus, you might also be better off checking the laptop’s charger port before getting to the complex motherboard circuitry. In case of any issue there, you can check out this (how to fix laptop charger port) to do the required troubleshooting.
And with this, let me close my talk on how to test a motherboard with a multimeter. If you still have any questions or confusion, feel free to ask below.