How We Test Power Supply Units

Introduction

The power supply unit (PSU) is the most important part of every electronic device, including, of course, computers. It is the heart of your system, since it feeds energy to the other components. Consequently, if the PSU fails, everything else fails with it. This is the reason most experienced technicians start a failure investigation from the PSU before proceeding to the rest of the components. And, consequently, this is why you should pay extra attention to your choice of PSU and not make a decision based exclusively on price. After all, a good PSU will do its job for quite a long time, far outlasting the rest of your expensive system components.

To properly review a PSU, expensive equipment is required, and the reviewer needs to know not only how to operate it, but also have sufficient knowledge about electronics and a PSU's design. The knowledge part is especially crucial, since not even the most expensive equipment can make a good PSU review if the reviewer doesn't know how to properly use it and what tests to conduct with it.

In our reviews, we examine the PSU's performance, noise and temperature ratings, along with the build quality of the units. We also judge the PSU's individual components, cables, connectors and even product specifications and packaging while providing a performance per dollar comparison.

MORE: All Power Supply Articles
MORE: Power Supplies in the Forums

Test Setup Overview

Currently, we use two fully equipped Chroma stations. The first Chroma station is able to deliver up to 2500 W of load and consists of two 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The second Chroma station can deliver more than 4 kW of load and consists of two 63601-5 and one 63600-2 mainframes. The aforementioned mainframes host ten 63640-80-80 [400 W] electronic loads in total along with a single 63610-80-20 [100 W x2] module.

Chroma loads are widely used by all PSU manufacturers and are pretty much the standard for PSU measurements. Finally, all of our equipment is controlled and monitored by a custom-made software suite that's highly sophisticated.

In addition to the Chroma loads, we also use two Chroma AC sources (6530 with 3kW and 61604 with 2kW max power), a Kesight DSOX3024A and a Rigol DS2072A oscilloscope, two Picoscope oscilloscopes (3424 and 4444), a Picotech TC-08 thermocouple data logger, two Fluke multimeters (models 289 and 175), a Keithley 2015 THD 6.5- digit bench DMM and two lab grade 3-phase power analyzers (N4L PPA1530 and PPA5530) along with a Yokogawa WT210 power meter.

To protect our Chroma AC sources we use two high quality online (meaning that they always run off the battery providing the best possible protection and line filtering) UPS systems with 3000VA/2700W capacity each. The first is from FSP (Champ Tower 3k), and the second is by Cyberpower (OLS3000E). The mains power is used only by the battery charger.

Our testing gear also includes a hotbox, which allows us to test a PSU at high ambient temperatures. Finally, we have three more oscilloscopes (a Rigol VS5042, a Stingray DS1M12 and a second Picoscope 3424), and a Class 1 Brüel & Kjaer 2250-L G4 Sound Analyzer, which is equipped with a type 4955-A low-noise and free-field microphone which can measure down to 5 dB(A) (we also have a type 4189 microphone that features a 16.6-140 dBA-weighted dynamic range).

The latest addition to our testing equipment is a Flir E4 infrared camera, which through some firmware modifications (many thanks to the fine folks at EEVblog's forums for this) now delivers a resolution of 320x240 pixels. In addition, we have several soldering and desoldering stations that we use during the dismantling process of every PSU we test. Test results are one thing, while checking out the build quality of a PSU is another. Finally, if we encounter any unusual results during the testing process, we examine the internals of a PSU to find out what is causing the issues.

Voltage Regulation Test

A PSU should be able to keep all of its rails within some predefined voltage ranges at all cases/loads. In Table 1, you will find these ranges (following the ATX v. 2.4 specification).

DC Output Voltage Regulation

Voltage NameRangeMinimumNominalMaximum
+12V1±5%11.40V12.00V12.60V
+12V2±5%11.40V12.00V12.60V
5V±5%4.75V5.00V5.25V
3.3V±5%3.14V3.30V3.47V
-12V±10%-10.80V-12.00V-13.20V
+5VSB±5%4.75V5.00V5.25V

Here's an example of a voltage regulation test results chart you'll find in each of our PSU reviews:

Efficiency

The 80 PLUS certification measures efficiency at 20-, 50- and 100-percent load of the PSU's max-rated capacity up to the Gold efficiency certifications. For the Platinum and Titanium levels, they also measure efficiency with 10 percent of the PSU's max-rated capacity load.

Simply put, if a PSU has an 80 PLUS certification, then it must have the equivalent efficiency required by the corresponding certification. However, 80 PLUS measures at a mere 23 °C (73.4 °F) ambient, whereas we measure efficiency at a higher ambient temperature. This means that, in many cases, a PSU that is certified to a certain efficiency category fails to deliver the same efficiency at higher temperatures in our tests.

Also, many PSUs are tuned to deliver high efficiency at or above a specified load percentage, usually the minimum that 80 PLUS measures at the corresponding efficiency level. But at loads lighter than that, their efficiency is pretty low. Since many of us run our systems for long periods at low-energy consumption modes, efficiency at light loads can be highly important. So it's wise to pay special attention to our light-load test results.

In our reviews, we measure efficiency at four different light loads: 20, 40, 60 and 100W.

The ATX specification also states that the efficiency of the 5VSB rail should be measured, too. In the table below, you will find the minimum 5VSB efficiency levels that the ATX specification recommends.

Recommended System DC And AC Power Consumption

LoadEfficiency
≤0.225W< 0.5W to meet 2013 ErP Lot 6 requirement (100V~240V)
≤0.45W< 1W to meet ErP Lot 6 requirement (100V~240V)
≤2.75W< 5W to meet 2014 ErP Lot 3 requirement (100V~240V)

Testing in Standby Mode

In 2010, the European Union released a guideline on Energy Related Products (ErP Lot 6), which states that every electronic device should have below 1W power consumption in standby mode. In 2013, this limit was further reduced to 0.5W. The same year, the EU also released the ErP Lot 3 guideline for computers and computer servers.

This is why we measure the consumption of a PSU in standby mode, which is something that would be difficult without our monitoring software since the readings at such low consumption levels have significant fluctuations. We have to average them over a significant period of time to provide enough accuracy.

Ripple Voltage

Ripple represents the AC fluctuations (periodic) and noise (random) found in the DC rails of a PSU. Ripple significantly decreases the life span of capacitors since it increases their temperature; a 10 °C increase can cut into a capacitor's life span by 50 percent. Ripple also plays an important role in overall system stability, especially when it is overclocked. 

The ripple limits, according to the ATX specification, are 120mV for the +12V and -12V rails, and 50mV for the remaining rails (5V, 3.3V and 5VSB). Nonetheless, in modern PSUs, we expect to find much lower ripple. It should be just a small fraction in high-end platforms with quality components and the proper amount of filtering capacitors. Below, you will find a schematic that analyzes a ripple waveform.

In the above schematic, four AC components can be identified:

  • Low-frequency ripple associated with AC mains frequency.
  • High-frequency ripple due to PWM of the main switches.
  • Switching noise that has the same frequency with switching PWM.
  • Non-periodic random noise that is not related to any of the above.

Here are a few examples of the typical ripple test results you'll find in our PSU reviews: 

Hold-Up Time And Power Good Signal

Hold-up time represents the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations as defined by the ATX specification without input power. Put simply, hold-up time is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption.

According to the ATX spec the PWR_OK is a “power good” signal. This signal should be asserted high, at 5V, by the power supply to indicate that the +12V, 5V, and 3.3V outputs are within the regulation thresholds and that sufficient mains energy is stored by the APFC converter to guarantee continuous power operation within specification for at least 17 ms. Conversely, PWR_OK should be de-asserted to a low state, 0V, when any of the +12V, 5V, or 3.3V output voltages falls below its under voltage threshold, or when mains power has been removed for a time sufficiently long such that power supply operation cannot be guaranteed. The AC loss to PWR_OK minimum hold-up time is set at 16 ms, a lower period than the hold-up time described in the first paragraph and ATX spec sets also a PWR_OK inactive to DC loss delay which should be more than 1 ms. This means that in any case the AC loss to PWR_OK hold-up should be lower than the overall hold-up time of the PSU and this ensures that in no case the power supply will continue sending a power good signal, while any of the +12V, 5V and 3.3V rails is out of spec.

The ATX specification sets the minimum hold-up time to 17 ms with the maximum continuous output load. In many cases, manufacturers use smaller capacitors in the APFC converter, resulting in a measurement of less than 17 ms. Manufacturers do this mostly to cut production costs, as these capacitors are expensive. The smaller bulk capacitors also improve efficiency by a little bit.

Measuring the hold-up time is a dangerous procedure since you have to connect an oscilloscope to the mains grid. Unless you are taking the right precautions, you never want to do this; it's dangerous and you could harm yourself and your equipment!

Inrush Current

Inrush current, or switch-on surge, refers to the maximum, instantaneous input current drawn by an electrical device when it is first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce significant inrush current as soon as they are turned on. A large enough inrush current can cause the tripping of circuit breakers and fuses, and may also damage switches, relays and bridge rectifiers. As a result, the lower the inrush current of a PSU right as it is turned on, the better.

We also noticed that the lower the input voltage, the lower the inrush current. Thus, when operating with 115 VAC, a PSU has much smaller inrush current compared with 230 VAC input. Both our Chroma AC source and the Yokogawa power analyzer have the ability to measure inrush current.

Transient Tests

In the real world, a PSU is always working with loads that change, depending on whether the CPU or graphics cards are busy. So, a decent PSU review should contain some tests with dynamic or transient loads. We conduct a variety of transient tests:

  • While the PSU is working at a 20 percent load state, a transient load is applied to the PSU for 200ms (10A at +12V, 5A at 5V, 5A at 3.3V and 0.5 A at 5VSB).
  • While working at 50 percent load, the PSU is hit by the same transient load.
  • In the next tests we use again the same starting points, 20 and 50 percent load states, however we increase the load-changing repetition rate from 5 Hz (200ms) to 50 Hz (20ms) and 1 KHz (1ms) and we also apply higher loads at +12V (15A) and the 5V and 3.3V rails (6A). This way we push even harder the PSU.

In all tests, we measure the voltage drops that the sudden load change causes. The voltages should remain within the ATX specification's regulation limits. Finally, we should also note that the latest ATX spec requires a load-changing repetition state of 50 Hz to 10 KHz for transient response testing. The only reason that we decided to keep the "slow" 5 Hz tests is to retain compatibility with our database, however once we have enough data with the higher speed transient tests, we will most likely stop conducting the less stressful 5 Hz tests.

We also conduct three transient tests where we measure the response of the PSU in its simpler turn-on phase. In the first test, we turn off the PSU, dial a full load at 5VSB, and then switch on the PSU. In the second test, while the PSU is in standby, we dial the maximum load that +12V can handle and start the PSU. In the last test, while the PSU is completely switched off (we cut off power or switch off the PSU's on/off switch), we dial the maximum load that +12V can handle, then switch on the PSU and restore power.

The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2V and for 5V is 5.5V).

Cross-Load Tests

Cross-load tests are the real deal, since they show a PSU's performance throughout its entire operating range. For the generation of the corresponding charts, we test at 28 to 30 °C (82.4 to 86 °F) ambient, and we set our loaders to auto mode through our custom-made software before trying more than a thousand possible load combinations with the +12V, 5V and 3.3V rails. The provided charts show load/voltage regulation along with ripple, efficiency and noise levels.

Acoustics/Noise Tests

It is hard to conduct proper acoustics measurements on a PSU since you have to isolate it from the loaders; they are way too noisy and will interfere with the readings. However, if you move the loaders far away from the test PSU, you need long connection cables, which incur increased resistance. Power losses become significant in that case.

Thankfully, we found a way around these issues, and with the help of a fully featured hemi-anechoic chamber, we are able to conduct accurate sound measurements using a Class 1 Sound Analyzer.

We measure the fan's noise from one meter away. The noise measurements are conducted with a Class 1 Bruel & Kjaer 2250-L G4 Sound Analyzer, equipped with a type 4955-A low-noise and free-field microphone which can measure down to 5 dB(A). We also have a type 4189 microphone that features a 16.6-140 dBA-weighted dynamic range. The sound analyzer is installed into a hemi-anechoic chamber which allows for lower than 6 dB(A) ambient noise. A Bruel & Kjaer Type 4231 is used before every noise measurement, to calibrate the sound analyzer.

Protection Features Evaluation

All power supplies have to be equipped with various protections, which also includes the system that is fed with power. You can learn more about PSU protections if you read the corresponding section of our PSUs 101 article.

The most important protections are the following:

  • Over Current Protection (OCP): The single +12V rail PSUs usually don’t have OCP on this rail, but they should have OCP on the minor rails, including 5VSB.
  • Over Power Protection (OPP): Unfortunately most PSUs have the OPP triggering point set significantly higher than their nominal max power output. This is mostly done to deal with load spikes, which could trigger OPP and shut-down the system, however OPP is there for a reason and it has to be properly configured in order to serve its purpose.
  • Over Temperature Protection (OTP): Since the ATX spec recommends at least 50 °C operating temperature for continuous full power delivery, a PSU has to have an appropriate OTP triggering point, if it is equipped with OTP of course. In PSUs with only a 40 °C rating, OTP’s triggering point inevitably will be lower.
  • Over/Under Voltage Protection (OVP/UVP): These protections only kick in when voltages surpass or go below a specific level. Given that the corresponding ATX limits are practically dangerous for the system’s health, and the fact that there is no safe way to test these protections, we decided not to deal with them, for the moment at least.
  • Short Circuit Protection (SCP): This is a basic protection that all PSUs should have. If there is a short-circuit in any of the rails, the PSU must immediately shut-down.
  • Power Good Signal (PWR_OK): This signal has to drop when any of the +12V, 5V or 3.3V output voltages goes out of spec.
  • No-load Operation (NLO): The PSU must operate normally even when there is no load on its outputs.
  • Surge & Inrush Protection (SIP): The design must include a Metal Oxide Varistor (MOV) or a Transient Voltage Suppression (TVS) diode, both of which provide protection against voltage spikes coming from the mains network. In addition, the platform must be equipped with inrush current protection. The most common way of lowering the inrush current during the PSU's start-up phase is by using an NTC (Negative Temperature Coefficient) thermistor, along with a bypass relay, which allows the thermistor's fast cool down.

In our methodology we consider that the OCP or OPP aren’t configured properly if their triggering points are set above 130%. Please note that a PSU might be able to deliver much more than its nominal power under normal ambient temperatures, but at higher temperatures this won’t be the case, and if OPP is set too high then most likely the PSU will be destroyed, especially if OTP is absent. In addition, if we notice any load regulation or ripple suppression issues during our OPP tests, we consider this protection to be improperly configured.

An evaluation example of a PSU’s protection features follows.

Protection Features
OCP12V: -
5V: >130%
3.3V: >130%
5VSB: >130%
OPP>125%
OTPYes (at 46 °C ambient)
SCP12V: Yes
5V: Yes
3.3V: Yes
5VSB: Yes
PWR_OKProper Operation
NLOYes
SIPSurge Protection: MOV
Inrush Protection: NTC & Bypass Relay

PSU Testing Equipment In Detail

Chroma Electronic Loads

The electronic loads are the most essential, and the second-most expensive component in our lab. A load tester simulates the load (static or dynamic) and gives us the capability to stress a PSU to its limits.

All measurements are performed using two fully equipped Chroma stations. The first Chroma station is able to deliver up to 2500 W of load and consists of two 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The second Chroma station can deliver more than 4 kW of load and consists of two 63601-5 and one 63600-2 mainframes. The aforementioned mainframes host ten 63640-80-80 [400 W] electronic loads in total along with a single 63610-80-20 [100 W x2] module.

The electronic loads would be useless if we didn't have the proper testing fixture at which the PSU's connectors are connected. In other words, this testing fixture is the bridge that links the PSU being tested with the electronic loads.

Monitor & Control Program

In order to monitor and control our Chroma loads, along with the rest of the equipment (oscilloscopes, temperature loggers, data loggers, power analyzer, hotbox heating elements etc.), we developed a software suite which can also record and analyze all output data.

The development of this program started in early 2010 and is still an ongoing process since new features are added on a regular basis, while old ones are improved. The software suite provides even more capabilities to the Chroma loads that we use, making the PSU testing procedure much easier and accurate at the same time. Another advantage of this software is that it can easily adapt to various types of electronic loads and testing equipment. So if, in the future, we decide to move to another testing platform, the transition process will be almost painless.

Chroma 6530 AC Source

This is the most expensive part of our testing equipment, surpassing even the cost of both of our Chroma mainframes, along with their loads. Nonetheless, it fully justifies its high cost by providing us with the ability to simulate different power-line disturbance conditions. It allows us to simulate a complex mains supply waveform, if needed, while delivering a steady input voltage. It also filters most external noise from the power grid, which can seriously distort ripple measurements.

In addition, an AC source like the Chroma 6530 is capable of simulating all sorts of voltage dips, interruptions and variation waveforms showing the PSU's response under similar scenarios. Finally, this AC source can deliver up to 3kW of power, facilitating the evaluation of any PSU available on the market today (even Super Flower's 2kW unit) without the slightest problem.

Besides the Chroma 6530 AC Source, we also have the lower-end Chroma 61604 at our disposal, which provides up to 2kW of power. This AC source was pushed to its limits during the evaluation of PSUs with over 1.5kW capacity, so we replaced it with the stronger Chroma 6530. Our testing equipment also includes a variable transformer (variac), which is able to deliver up to 3kW.

Power Meter/Analyzer

A power meter provides only basic functions, whereas a power analyzer is a highly sophisticated and expensive piece of equipment able to deliver accurate power and harmonics measurements. We use two N4L power analyzers (PPA1530 and PPA5530) to measure the exact (AC) wattage that the PSU pulls from the power grid, along with other crucial parameters like power factor and AC volts/amps. Given a known power consumption on the DC side, we can easily calculate the efficiency (DC watts/AC watts) of a PSU in real time through our testing software suite. Our backup power analyzer is a Yokogawa WT210.

Every PSU reviewer needs a good power meter, or, ideally, a power analyzer, with a high sampling rate. You see, sometimes the APFC stage of a PSU can be tricky, resulting in inaccurate readings with cheap Kill-a-Watts. Unfortunately, a power analyzer is pretty expensive. But if you want to have accurate readings, especially in light loads (<100W) or demanding ones (>1000W), then you have no other choice. As backups, we have a GW Instek GPM-8212, one of the best power meters for its price, and a Prova WM-01 power analyzer. Our main instrument for measuring the electrical characteristics of the  PSU is the Yokogawa WT210, which reports directly to the control/monitor program, allowing the calculation of a PSU's efficiency in real time.

Oscilloscope

To measure voltage ripple on the DC rails with static or dynamic (transient) loads, an oscilloscope is a one-way road. Back in the early days, most PSU reviewers used the limited bandwidth (250kHz) Stingray DS1M12 because it was affordable and did a pretty good job. However, for high-speed transient response tests, a higher-bandwidth oscilloscope is needed. We use a Picoscope 3424 scope and a Picoscope 4444 differential scope for ripple- and transient-response measurements, while our hold-up tests are conducted with the help of a Keysight DSOX3024A scope.

Spectrum Analyzer

A spectrum analyzer (SA) is a piece of equipment that measures the magnitude of an input signal versus frequency and its main purpose is to measure signal power. In a SA the horizontal axis is for frequency while the amplitude is shown on the vertical axis. We have an SA in our lab to perform some basic EMC Pre-Compliance testing. Our main SA is a Signal Hound BB60C which features excellent performance and at the same time it doesn't break the bank. The BB60C has a pretty wide range, at least for our purpose, from 9 KHz to 6 GHz, and its dynamic range is from -158 dBm to +10 dBm. The provided software, called Spike, is easy to use and provides many interesting functions. Besides the SA we also got two Aaronia antennas, one omnidirectional (OmniLOG 70600) and one directional (HyperLOG 7060). We want to thank Aaronia for providing us these antennas at a significant discount. We need lots of expensive equipment to conduct proper PSU reviews and we really appreciate when a company supports us.


We would like to note here that the BB60C Spectrum Analyzer was kindly provided by Signal Hound and the least we can say to them is a huge "thank you" for their support.

We also have in our disposal a Rigol DSA815-TG which might not be fully compatible with the CISRP 16-1-1 requirements, but still can be used to effectively check the EMC of a device. The DSA815-TG is among the best bang for the buck EMI receivers available on the market today and provides options that some years ago could be found only in super-expensive equipment. We would like to thank Rigol for providing us the EMI option, which will allow us to perform all relevant tests easily.

LISN Device And EMC Probes

In order to perform correctly the EMC Pre-Compliance tests we need a LISN (Line Impedance Stabilization Network) device, which very briefly is a low-pass filter that removes all unwanted noise from the AC line that feeds the under test device (in this case a PSU). In addition, a LISN device provides a stable line impedance along with an RF (Radio Frequency) noise measurement jack, to which we can connect our SA to measure EMI noise. Besides a LISN we also have in our disposal an EMC probe set which came set with a wideband amplifier. With these probes we are able to locate interference sources inside any device, since they act as antennas picking radiated emissions from electronic components, even PCB traces.

Both the LISN device and the EMC probe set were kindly provided by Tekbox Digital Solutions and we thank them very much for their support.

Multimeter

Although almost all load testers are equipped with their own current/voltage meters, a good multimeter is always useful in a PSU review. It doesn't need to be a 4.5-digit one. However, it needs to be recently calibrated in order to provide accurate values.

We have a large number of multimeters at our disposal, including a high-end Fluke model with 4.5 digits (289), a mid-range one (175) and a high-end bench multimeter with 5.5-digit precision (Keithley 2015 TDH). We also have a Labjack U3-HV multifunction data acquisition (DAQ) device to obtain some real-time readings from the PSU being tested. Finally, we have a DMMCHECK Plus device, through which we are able to check the accuracy of all equipment we use for measurements.

Hotbox

We strongly believe that there is no point in measuring a PSU at room temperature since it will spend all its life inside a case where temperatures will be much higher. So, the most interesting test results are the ones obtained with the PSU operating at temperatures above 40 degrees Celsius (104 degrees Fahrenheit) ambient. The ATX specification states that a PSU should be able to operate at ambient temperatures of 10 to 50 °C (50 to 122 °F) at full load, with a maximum temperature change rate of 5 °C (41 °F) per 10 minutes, but no more than 10 °C (50 °F) per hour.

The 80 PLUS organization tests efficiency at only 23 °C (73.4 °F) ambient, which, in our opinion, is way too low for this purpose. Performance at high operating temperatures is what separates the good PSUs from the mediocre and bad ones. A well-built power supply should be able to output its full power continuously at up to 50 °C (122 °F), while lower-grade ones can only hang at up to 40 °C. Finally, low-quality PSUs are restricted to 25 °C (77 °F).

In order to set a standard for our PSU reviews, we decided to conduct our full load tests at 45 °C (113 °F). In case a PSU explodes or delivers a really poor performance under the above conditions, we note this in the review and subtract the corresponding performance points from its overall performance score.

To be able to test at high ambient temperatures, an environmental chamber is needed. We constructed our own hotbox with heating elements that are software-controlled and can operate in a fully automatic mode. That is, we set the desired temperature and the heating elements operate accordingly in order to keep it within a specified range.

Digital Thermometer/Temperature Logger

An accurate digital thermometer or temperature logger is essential for the measurement of the PSU's intake and exhaust temperatures. For this purpose we use a Pico TC-08 temperature logger with eight probe inputs, and a CHY 502 thermometer as a backup, with two thermocouple inputs.

Sound Meter/Analyzer

Similar to the power meter and the power analyzer case, the difference between a sound meter and a sound analyzer is huge. A sound meter can only report basic sound measurements, while a sound analyzer provides a detailed look at the output noise, including frequency analysis, FFT sound and vibration, sound recording, and so on.

The American National Standards Institute (ANSI) classifies sound level meters in three different types: 0, 1 and 2. Type 0 is used in laboratories, while Type 1 is used for precision measurements in the field and Type 2 for general-purpose measurements. The better Type 2 sound meters usually have an accuracy of ±2 dB(A), while a Type 1 sound meter usually has ±1 dB(A) accuracy. IEC standards divide sound level meters into two "classes." Class 1 instruments have a wider frequency range and a tighter tolerance for error than the lower-cost Class 2 units.

Another important factor in noise measurement is how "low" a sound meter can go. For example, most inexpensive sound meters simply cannot measure anything below 30 dB(A) because of their low-quality microphones. To be able to measure below this, you need to invest in a good Type 1 or Class 1 meter with a decent mic.

Our Class 1 Brüel & Kjaer 2250-L G4 Sound Analyzer is equipped with a type 4189 microphone that allows it to measure noise down to 16.6 dB(A). To fully exploit its capabilities, we built a mini-anechoic chamber, inside which we were able to measure down to 17 dB(A) during quiet hours. However, a good sound analyzer is worthless if it's not calibrated regularly (ideally, before any sound measurement). For this reason, we use a Brüel & Kjaer type 4231 sound calibrator, which provides a calibration accuracy of ± 0.2 dB(A).

Infrared Camera

An infrared (IR) camera isn't an essential piece of equipment for a PSU review, but it can be useful if you need to check the thermal dissipation and the cooling fan's performance. We use a Flir E4 and, thanks to the ingenious folks at EEVblog, we managed to raise its resolution to 320x240 pixels.

Soldering and De-Soldering Tools

In addition to the required testing equipment, we also have the tools to fully dismantle a PSU for a build quality check. We use a Thermaltronics TMT-9000S soldering and rework station. We also have a Hakko 808 desoldering gun, an AOYUE 474A desoldering station and a Weller WSD 81 soldering station.

PSU Reviewing Is Hard Work!

In this article, we described the necessary equipment needed for a proper PSU review and outlined our testing methodology, which includes a rich variety of tests. As you have probably noticed, PSU reviewing is a complex, time consuming and expensive task. Even if you possess all of the necessary tools, you need to have the proper electronics background as well so that you can dismantle the PSUs without damaging them or harming yourself. You also need to be able to provide an accurate analysis of the PSU's platform and its components in order to judge its build quality. PSU reviewing admittedly is a hard job, but someone has to do it and, thankfully, we enjoy the work! 

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  • JPNpower
    Nobody can fault you guys for not being thorough enough! All we can wish for is that you do these tests a bit more often. I'm at a loss how to navigate the PSU field, and a "Best Picks" section for PSU's would be tremendously helpful.
  • Nuckles_56
    Really good article, it is now nice and clear how you guys go and test the power supplies, and as JPNpower said, no one can fault you guys for not being thorough enough.
  • ykki
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.
  • Kewlx25
    Interesting!
  • damric
    Looks legit, Aris.

    THW used to be the laughing stock of PSU reviews, but your recent reviews have changed all of that.

    Keep up the good work!
  • damric
    Quote:
    Nobody can fault you guys for not being thorough enough! All we can wish for is that you do these tests a bit more often. I'm at a loss how to navigate the PSU field, and a "Best Picks" section for PSU's would be tremendously helpful.

    Quote:
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.


    I'll make one and submit it through bb-71 to get stickied.
  • ykki
    Anonymous said:

    I'll make one and submit it through bb-71 to get stickied.


    OK. If someone makes a psu list I'd rather see it from you (or the mods). Good luck.
  • damric
    Anonymous said:
    Anonymous said:

    I'll make one and submit it through bb-71 to get stickied.


    OK. If someone makes a psu list I'd rather see it from you (or the mods). Good luck.


    It will be a group effort for sure :)
  • iam2thecrowe
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.
  • ykki
    Anonymous said:
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.

    Or more fake reviews.
  • shrapnel_indie
    As to PSU lists, I know there has been a few around for a LONG time now. Many are not kept up and therefore lack newer PSU units and contain many PSU units no longer available on the market. SOME lists are full of opinions based on a small handful of anecdotal cases and personal biases too. The one with the most upkeep, and therefore the most up to date one I know of is over in the NewEgg EggXperts community and as far as I can tell isn't biased, but is based off solid reviews and real experiences.

    https://community.newegg.com/eggxpert/computer_hardware/f/135081/t/45344.aspx

    Mind you though, there are some PSUs that may make Tier 3 that many will condemn as if it was a tier 5 unit for quality reasons though, such as the Corsair CX(M) series because allegedly they die as soon as the warranty runs out. I cannot personally verify that at least yet because the only unit I have of that series (a CX600) hasn't hit that time yet. It is in a 6-core i7 X79 platform with a lower end workstation GPU so power demand isn't really all that high.


    Quote:
    Anonymous said:
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.

    Or more fake reviews.


    I tend to agree here. Letting manufacturers test and publish the results will do no good. Look at the manufacturers, the ones that fib on how much power their PSUs will deliver: I think we could almost guarantee fake reviews there. It's bad enough when you surf the web for a review on a product and the reviews you find just vomit out what the manufacturer's marketing department released on the item, but to let them tell us how their test had something pass with flying colors when reputable testers (such as OklahomaWolf over on JonnyGuru) test the same unit and find it to be horrific.
  • iam2thecrowe
    Anonymous said:
    As to PSU lists, I know there has been a few around for a LONG time now. Many are not kept up and therefore lack newer PSU units and contain many PSU units no longer available on the market. SOME lists are full of opinions based on a small handful of anecdotal cases and personal biases too. The one with the most upkeep, and therefore the most up to date one I know of is over in the NewEgg EggXperts community and as far as I can tell isn't biased, but is based off solid reviews and real experiences.

    https://community.newegg.com/eggxpert/computer_hardware/f/135081/t/45344.aspx

    Mind you though, there are some PSUs that may make Tier 3 that many will condemn as if it was a tier 5 unit for quality reasons though, such as the Corsair CX(M) series because allegedly they die as soon as the warranty runs out. I cannot personally verify that at least yet because the only unit I have of that series (a CX600) hasn't hit that time yet. It is in a 6-core i7 X79 platform with a lower end workstation GPU so power demand isn't really all that high.


    Quote:
    Anonymous said:
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.

    Or more fake reviews.


    I tend to agree here. Letting manufacturers test and publish the results will do no good. Look at the manufacturers, the ones that fib on how much power their PSUs will deliver: I think we could almost guarantee fake reviews there. It's bad enough when you surf the web for a review on a product and the reviews you find just vomit out what the manufacturer's marketing department released on the item, but to let them tell us how their test had something pass with flying colors when reputable testers (such as OklahomaWolf over on JonnyGuru) test the same unit and find it to be horrific.


    Ok, so maybe they have to get an independent party to test them, and allow the public to access the results. Anything that will get the rubbish mislabeled psu's off the shelf. No other device can be mislabeled and sold based on lies, why is it the humble ATX psu can somehow circumvent the false advertising laws? Nvidia copped a lot with their 970 misinformation yet we let these PSU manufacturers get away with it?
  • JPNpower
    Anonymous said:
    @JPNpower= I also think a best psu for the money article would be nice but the power supplies in the market pretty much stay the same. We may go for months before seeing any change in the list.


    There's not problem with that. As long as good units stay on the list, and discontinued units are left out, I would love such a list. 'Cause with different OEM's and brands and ratings and such, it really is a swamp.

    I would love a forum effort to, and would definitely contribute what little knowledge that I have. Although, I asked for a Toms official ver. cause their montor/cpu/gpu/ssd/etc lists are so good and straightforward even to the newest of users.
  • JPNpower
    Anonymous said:
    Anonymous said:
    As to PSU lists, I know there has been a few around for a LONG time now. Many are not kept up and therefore lack newer PSU units and contain many PSU units no longer available on the market. SOME lists are full of opinions based on a small handful of anecdotal cases and personal biases too. The one with the most upkeep, and therefore the most up to date one I know of is over in the NewEgg EggXperts community and as far as I can tell isn't biased, but is based off solid reviews and real experiences.

    https://community.newegg.com/eggxpert/computer_hardware/f/135081/t/45344.aspx

    Mind you though, there are some PSUs that may make Tier 3 that many will condemn as if it was a tier 5 unit for quality reasons though, such as the Corsair CX(M) series because allegedly they die as soon as the warranty runs out. I cannot personally verify that at least yet because the only unit I have of that series (a CX600) hasn't hit that time yet. It is in a 6-core i7 X79 platform with a lower end workstation GPU so power demand isn't really all that high.


    Quote:
    Anonymous said:
    It would be nice if all manufacturers could do this testing and publish results when they build the things, or even better for it to be a requirement. Then at least there would be less junk PSU's on the market.

    Or more fake reviews.


    I tend to agree here. Letting manufacturers test and publish the results will do no good. Look at the manufacturers, the ones that fib on how much power their PSUs will deliver: I think we could almost guarantee fake reviews there. It's bad enough when you surf the web for a review on a product and the reviews you find just vomit out what the manufacturer's marketing department released on the item, but to let them tell us how their test had something pass with flying colors when reputable testers (such as OklahomaWolf over on JonnyGuru) test the same unit and find it to be horrific.


    Ok, so maybe they have to get an independent party to test them, and allow the public to access the results. Anything that will get the rubbish mislabeled psu's off the shelf. No other device can be mislabeled and sold based on lies, why is it the humble ATX psu can somehow circumvent the false advertising laws? Nvidia copped a lot with their 970 misinformation yet we let these PSU manufacturers get away with it?


    To be fair, that seems to be the whole point of the "80plus" certification. There are very few bad true 80plus PSU's I heard.
  • chimera201
    I hope Tom's do some reviews of budget PSUs. I want to see some explosion! All you do is test high end units that caters to less than 10% of the PSU buyers
  • coolkwc
    For the electronic load tester, it would be great if the wires connected from PSU to load tester are keep short, if not possible, as thick as possible, or multiple wires connected in parallel. It would become nasty when tested current is very high, the losses through the wiring will be greater, so basically the PSU will need to output more power than the load tester setting, in turn it will affect the efficiency reading as well. I remembered couple of PSU reviews in here revealed the efficiency reading is slightly lower than manufacturer's claim, maybe this was the culprit. Just my little opinion.
  • Aris_Mp
    Chroma loads have current sense wires so there is no problem there. Also the cables I use are the original Chrona ones, designed specifically for this task.
  • InvalidError
    One problem with PSU reviews is that they are testing brand-new PSUs out-of-the-box. The true long-term stability and reliability of a PSU is not known for sure until a few years of use under medium-high load.
  • unityole
    @invalidError

    samethings can be said for most electronics, its tough.
  • iam2thecrowe
    "To be fair, that seems to be the whole point of the "80plus" certification. There are very few bad true 80plus PSU's I heard. "
    Unfortunately there are psu's that have fake 80 plus logo's on them

    Anonymous said:
    One problem with PSU reviews is that they are testing brand-new PSUs out-of-the-box. The true long-term stability and reliability of a PSU is not known for sure until a few years of use under medium-high load.


    yes, i guess thats why its important to take quality of components like capacitors, and any hot spots from poor airflow into account in the reviews also.