Testing the Power Supply Unit (PSU) comes first when dealing with a computer that’s not pulling its weight (or, I say, not turning on). Why? Because a whopping 90% of computer issues might just find their roots in a wonky PSU.understanding the topic

A faulty PSU isn’t merely a computer’s way of taking a sick day. Oh no, it throws a whole parade of glitches your way—from the refusal to boot up (giving you that lovely black blank screen) to spontaneous shutdowns or restarts while you’re knee-deep in something crucial. And if things get really hairy, say hello to the dreaded Blue Screen of Death (BSOD), ready to crash your system and possibly wave goodbye to some precious data that you’ve been working on.

Now, to pin the blame on the PSU, there are various diagnostic steps to run through. These steps act like a checklist to check if the PSU’s up to the task or if it’s the troublemaker behind the scenes.

Lets See How To Test A PSU Without Motherboard

Examining a PSU outside of the computer isn’t rocket science. You don’t need to be an electrical whiz to pull it off. Just grab some basic tools like a “Screw Driver”, a “Paper Clip”, and either a “Multimeter” or a “PSU Tester”. With these buddies by your side, you’re all set for the testing adventure.

These methods I’m about to walk you through work like a charm for different PSU models—whether it’s AT, ATX, or eATX. The beauty of it? The steps stay the same no matter what kind of PSU you’ve got. That means you can accurately check and judge its performance, regardless of its fancy title.

So, are you ready to test your computer’s PSU? But, first things first, you’ve got to take it out of the computer cabinet. But hold your horses! Before doing that, it’s super important to disconnect all the cables hooked up to the components inside the cabinet. That means everything from the SATA Connector to the 24-Pin ATX Connector needs to be unplugged.ALL PSU Cables

Make sure you’re thorough—disconnect every cable linked to the internal components in the cabinet. This way, when you take out the PSU, you’ll have a nice, clean testing zone without any pesky interference from connected stuff. This clean setup lets you troubleshoot and figure out what’s going on with the PSU accurately.

disconnect all the cables connected from PSU

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Method 1: Testing Using a Paper Clip 

To test a PSU using a paper clip, grab one and straighten it out or use a piece of wire that can do the trick. Make it into a “U” shape or something that can effectively kickstart the PSU. Now, let’s find the connector on your PSU—usually, it’s the bigger one, either the 20-Pin or the 24-pin ATX. Look for the odd one out, the green wire nestled in there. It’s the only green wire in the whole bunch, so it’s easy to spot.

But wait, if all the wires in your PSU look the same, here’s a trick: position the ATX or eATX connector so that little notch is facing down. Now, count the pins from the right side and stop at the 4th pin. That’s where you’ll find that special green wire you need for the test.

count the pins from the right side and stop at the 4th pin.

Once you’ve found that green wire, it’s time for the next step: making a connection between this green wire and the ground. Look for any black wire close to the green one. You can use either the 5th or 3rd Pin, both of which have black wires neighboring the green wire.

Jumper wire Connection

After you’ve created this jumper connection, plug the power into the PSU and flip the switch to turn on the electricity. This move basically shortcuts the PSU’s circuit, getting it up and running outside of your computer’s cozy cabinet.

PSU turned ON with FAN

What’s happening at this point?

If the PSU fans are spinning smoothly, that’s a great sign—pretty much a 95% guarantee that everything’s working just fine. But hey, that 5% uncertainty hangs around because sometimes the power supply might work, but it’s not giving the right voltages to the inside bits, causing problems.

But in case, the PSU fan doesn’t start at all or maybe starts but then stops suddenly, that’s a red flag. It means the PSU might be faulty and need replacing. Here’s a neat trick: Try gently nudging the fan with a thin stick. Sometimes, it gets stuck, even though the power supply itself is doing okay.

Method 2: Testing Using a PSU Tester

Using a power supply tester is like a basic detective move when you’re trying to figure out what’s up with your computer’s power supply unit (PSU). You don’t need fancy gear or expert skills for this. This little tool is a lifesaver—it checks if the different voltage parts in the PSU are doing their job right, making sure they’re delivering power properly to your computer’s bits and bobs.

Here’s how to use a power supply tester step-by-step:

  1. Connect the ATX 20or 24-pin Motherboard Power Connector and the ATX 4-pin CPU Power Connector to the tester. Depending on your PSU, you might have different connectors like a 6-Pin or 8-Pin. If so, connect them one at a time along with the 24-pin connector.Connecting Connectors to PSU tester
  2. Plug the power supply into an outlet and switch it on using the rear switch. Some PSUs don’t have this switch, so just plugging it in will power it up.
  3. Hold down the ON/OFF button on the power supply tester. This should start the fan inside the power supply. But hang on, just because the fan’s spinning doesn’t mean everything’s peachy. Sometimes, the fan might not spin even if the PSU is working. Keep testing to be sure.
  4. Look at the LCD display on the power supply tester. It should show numbers for all the voltages the PSU can deliver—like +3.3 VDC, +5 VDC, +12 VDC, and -12 VDC. If you see “LL” or “HH” or if the screen is dark, that’s bad news. It means the PSU isn’t doing its job right and needs replacing. PSU Tester showing low voltage
  5. Focus only on the LCD screen for readings. Ignore any other lights or indicators not showing up on the display.
  6. Check if the reported voltages by the tester match the approved limits. If any voltage falls outside the range or the PG Delay Value isn’t between 100–500 ms, think about getting a new power supply. The tester will probably flag an error for wrong voltages, but for safety, double-check yourself.
  7. If all the reported voltages are within limits, congrats! Your power supply seems to be doing fine. If you want to keep testing individual peripheral connectors, go ahead with the process.
  8. Turn off the switch on the back of the power supply and unplug it from the wall.
  9. Now plug in either a 15-pin SATA Power Connector or a 4-pin Molex Power Connector into the designated slot on the power supply tester. Make sure to connect only one peripheral power connector at a time. Connecting more than one might mess up the testing accuracy, though it probably won’t damage the tester.
  10. Keep the motherboard power connectors attached to the tester while you’re testing other power connectors.PSU tester
  11. Now again, switch on the power supply using the rear switch, if it has one.
  12. Look at the +12V, +3.3V, and +5V lights on the tester. These lights match up with the voltages coming through the connected peripheral power connector. They should light up accordingly. If they don’t, it might mean the power supply needs replacing.
  13. Keep repeating this process for each power connector, starting from the previous step each time. Test one connector at a time, except for the motherboard power connectors that stay connected throughout the whole thing.

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Method 3: Testing Using a Multimeter

Before you dive into testing the PSU using a multimeter, make sure you’ve hooked up that jumper wire as detailed in ‘Method 1’. This step is a big deal because having that jumper wire in place lets you turn on the PSU outside of the computer setup. This setup is key for getting precise voltage readings and running diagnostics with the multimeter.

  1. Turn on the Multimeter and Set to VDC:
    • Switch on your multimeter and set the dial to the VDC (Volts DC) setting. This allows the multimeter to accurately measure direct current (DC) voltages.
    • If your multimeter doesn’t automatically adjust its range, manually set it to 20V to ensure accurate readings within that range.
  2. Testing the 24-pin Motherboard Power Connector:
    • Use the black probe (negative) of the multimeter and connect it to any pin representing the ground wire on the 24-pin Motherboard Power Connector. Ground pins act as reference points for voltage measurements.
    • Use the red probe (positive) to test the specific power lines. The 24-pin connector carries different voltages like +3.3 VDC, +5 VDC, -5 VDC (if available), +12 VDC, and -12 VDC distributed across multiple pins.Testing the 24-pin Motherboard Power Connector
  3. Pinout Reference and Comprehensive Testing:
    • Refer to the ATX 20 or 24-Pin Connector Power Supply Pinout to identify pins corresponding to various voltage lines.
    • Test each pin associated with a specific voltage to ensure proper voltage delivery and connection.connector_atx_pinout
  4. Evaluate Results and Determine Action:
    • Analyze the recorded voltage readings. If any voltages fall outside the approved tolerance range, it could signal power supply issues.
    • Readings exceeding permissible limits might indicate a need for power supply replacement.
    • If all voltage readings are within specified tolerance limits, it suggests the power supply is functioning properly and isn’t defective.

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Using the PSU test and Multimeter is a great way to start troubleshooting a PSU for basic issues. However, what I consider as “Advanced Troubleshooting” involves a more detailed process—testing the voltage lines under load, which can be a bit more challenging.

Sometimes, a power supply unit (PSU) might seem fine when tested normally but could show problems when it’s under a heavy load. For example, during intense activities like gaming or rendering, your system might suddenly reboot because the 12V supply can’t keep up due to a drop in voltage caused by not having enough current (measured in amperes) to handle the load.

This advanced troubleshooting means checking how the PSU performs under these heavy load conditions. It needs techniques that mimic the tough situations the PSU might face during heavy use, giving a more accurate idea of whether it can provide steady power without voltage drops or interruptions.

While using a multimeter to test the PSU’s static voltages is helpful, evaluating its performance under load needs special gear or methods. This process helps technicians measure and understand how the PSU works when the system is running at its max, imitating real-life situations.

By doing these advanced load tests, you can uncover any possible weaknesses or issues within the power supply that might not show up during regular voltage testing. It gives a better understanding of how the PSU behaves under pressure, giving a more complete view of its reliability and performance when pushed to the limit.

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