How to test a Power Supply with a Multimeter-Diy Guide

A Psu or dc power supply mainly energizes internal components of a pc or other electronics components after conversion of ac mains voltage to dc 5v,12v. In case of power failure of a computer in presence of electricity, the first step should be to check its power source. Here we’ll tell you a manual method to test dc power supply by multimeter.

After that, you can evaluate if the supply is working well or has to be replaced. The good point is it doesn’t require you to be an experienced electrician to execute this test. With some simple steps and minor multimeter know how you can certainly do it.

Below, we have mentioned some simple steps involved in “how to test a power supply with multimeter”.

  1. Do all necessary saftey measures(wearing saftey gloves,shoes etc) first as you have to deal directly with live voltage points.
  2. Now power off the computer, also disconnect power plugs from mains supply. Dissconnect all other data cables coming to psu or cpu unit.
  3. Short pin 15 and 16 of power supply with 24 pin motherboard connecter to check power flow further.
  4. Some countries have 115v general household power supply, other run on 220v systems so confirm that your power supply is adjusted on your’s country mains voltage.
  5. After turning on multimeter set its range to ac 200 to 300 v and check voltage coming from outlet.
  6. Now connect power supply unit plug with outlet mains supply, this should result into turning on of fan insude power supply.
  7. Turn multimeter’s range from ac to dc volts upto 20vdc.
  8. Now connect black or neutral probe of multimeter to ground point and red probe to any point in 24 pin connector. It should give various voltage outputs like 3vdc, 5vdc , -3vdc, -5vdc , 12vdc and -12vdc. See fig 1.1 .
  9. Check every point for confirmation that all supply points are working well.
  10. If you found one or more points missing output voltage or giving abnormal volts that will indicate some problem in power supply.
  11. Turn of power supply to psu and recoonnect all plugs,devices with psu.
  12. Connect power plugs to psu and turn on your computer.
  13. Make sure to turn off multimeter aswell to safe battery timings.
power supply 24 pin illustration
fig 1.1

How to test a Tv Power supply with Multimeter

After learning how to test a computer power supply, checking tv power supplies is actually a matter of seconds even for some diy enthusiast. Troubleshooting itself is not much complex as we think only if we learn and follow it step by step.

Generally, power supply of lcd tv is located in the middle of tv body on the backside. Where large box of the circuit is hooked with variety of electronic components like capacitors, transformer, ic,s, etc.

  1. Check outlet supply socket first if it’s working well and voltage level is normal.
  2. Make sure that your tv is not plugged alongwith several other electric equipments like refrigerator, washing machine, iron that usually consume a lot of power.
  3. Now connect power plug of your tv to a working power socket.
  4. Now turn on your multimeter and switch range to 10v dc if multimeter is not auto ranging. Otherwise multi meter will automatically detect the range.
  5. Now start testing voltage values of each connector or other circuits and note down values either they are under thier respected range or not. For this purpose use catalog of your lcd tv electric circuitry diagram.
  6. Now conduct another manual test, for this plug a lamp into socket with tv and observe if it’s flickering while you were testing circuit with multimeter.
  7. If lcd screen and lamp is flickering it’s may be a sign of power fluctuation, in that case consult with an electrician immediately.

How to test a dc Power adaptor with Multimeter

Dc adaptor is a form of dc power supply. Most electronic devices and gadgets run on 3v , 5v , 12v, and 20v dc power sources mostly in the form of a battery or a direct dc power source like a dc adaptor. You might have a shaving trimmer or a toy that requires a power supply to recharge every time.

On a random day, you found that the adaptor isn’t charging your shaver machine when there is no issue with electricity. Now you may wonder how to test dc power adaptor with multimeter if you have one in your tools kit. You don’t need to worry anymore now, just follow these steps to find the possible fault.

testing adaptor(dc power supply) with multimeter
fig 1.2
  1. Turn on your multimeter, and switch the dial to dc 10v , 20v.
  2. Make sure that the socket where you’re connecting adaptor is in fine condition and have normal voltage output.
  3. Now connect red probe of multimeter with tip of adaptor charging pin and black probe with barrel(please see fig 1.2), never forget that black probe should not touch red probe or charging pin directly.
  4. Now check reading on multimeter display, it should give 12 to 12.5 v dc if it’s rated for 120/220vac to 12vdc.
  5. You should get an output more or less the same as its rated output voltage.
  6. A result which is significantly different from output voltage rating may be a sign of unregulated adaptor.


So now you’ve learned how to test power supply with help of a multimeter. We hope you didn’t find it hard to execute these simple tests. Damaged or faulty power supplies are extremely dangerous for a computer’s circuitry or whatever electronic device they energized.

So you should check them early to avoid further loss if ever encounter an unusual behavior of a power source. Sometimes a minor fault may lead to a serious catastrophe to never neglect these signs and do check your electronics equipments regularly.