Verax 300W PSU

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  • Very low noise level
  • Output over voltage protection
  • Short circuit protection on all output
  • Reset Table power shut down
  • Approved by:: T√úV, CSA, UL, NEMKO, FCC, CE
  • Internal 12 VDE fan
  • 100% burn-in under high ambient temperature (50C)
  • Vacuum-impregnated transformer
  • MTBF: 100K hours at 25C
  • 100% Hi-pot tested
  • Line input fuse protection


  • Remote ON/OFF Control
  • Passive PFC
  • Temperature range:
    • operating 0C~50C
    • storage -20C~+65C
  • Temperature coefficient: 0.01% / C
  • Transient response: output voltage recovers in less than 1ms max. following a 25% load change
  • Dielectric withstand: input / output 1800VAC for 1 second, input to frame ground 1800 for 1 second
  • Humidity: 5~95% RH
  • Efficiency: 65% min. 70% typical, at full load
  • Power good signal: turn-on delay 100ms to 500ms
  • Overload protection: 150% max.
  • Inrush current: 60A cold, 80A warm at 264 VAC
  • Over voltage protection:
    • +5V : 6.5V(max.)
    • +3.3V : 4.6V(max.)
    • +12V : 15.5V(max.)


AC Input
100~120 VAC / 200~240 VAC, 10 / 6A, 60 / 50Hz
DC Output
Load Regulation
Line Regulation
Ripple + Noise
50mV P-P
50mV P-P
120mV P-P
120mV P-P
100mV P-P
50mV PP
Min Current
Normal Current
Max Current
Max Power


There are five 4-pin Molex connectors and two floppy drive power connectors on three sets of 16" wires. Both the length and the number of connectors are modest but adequate. The main ATX and 12V connectors are on 20" wire sets. Plus there is the 6-pin 5 + 3.3V connector on another 20" wire set.


Parameters Tools Used
DC load on PSU DBS-2100 PSU load tester
Ambient temperature
Any number of thermometers
Fan voltages / DC line voltage regulation
Heath / Zenith SM-2320 multimeter
AC power
Kill-A-Watt Power Meter
Heath AD-1308 Real Time Spectrum Analyzer

The core PSU test tool on SilentPCReview's test bench is the DBS-2100 load tester, made (in Taiwan by D-RAM Computer Company) specifically for testing computer power supplies. The machine consists of a large bank of high power precision resistors along with an extensive selection of switches on the front panel calibrated in Amps (current) and grouped into the 5 voltage lines: +5, +12, -12V, +3.3, -5, +5SR. Leads from the PSU connect into the front panel. It is shown above with leads from a PSU plugged in.

To ensure safe current delivery, the DC output connector closest to the PSU on each set of leads is connected to the load tester. This ensures that the current is distributed to as many short leads as possible. When pushing a PSU to its full output, the heat generated in the wires and connectors can be an issue.

The PSU is tested at 4 DC output power levels, in the following sequence:

  1. 65W: Established as a typical power draw for most PCs at idle or light general use. (This is a NEW power level.)
  2. 90W: Established previously as a typical max power draw of a mid-range desktop PC.
  3. 150W: Usually the 50% point for a 300W model.
  4. Maximum: The rated maximum power of the PSU.

Care is taken to ensure that the load on each of the voltage lines does not exceed the ratings for the tested unit. The PSU is left running ~10 minutes at each power level before measurements are made.

The DBS-2100 is equipped with 2 individually fused AC outlets and 4 exhaust fans on the back panel. A bypass switch toggles the fans on / off so that noise measurements can be made. The resistors get very hot under high loads.

Kill-A-Watt AC Power Meter is plugged into the AC outlet on the side of the DBS-2100 in the above picture. The AC power draw of the PSU is measured at each of the 4 power loads. The Kill-A-Watt is used to measure:

Efficiency (in AC-to-DC conversion) at each power level. This is the efficiency figure provided by PSU makers. It is obtained by dividing the DC power output (as set on DBS-2100 load) by the AC power consumption. Efficiency varies with load, and also temperature. PSUs seem to run more efficiently when warmer, up to a point. Generally, they are least efficient at low power and most efficient at 40~80%. The main advantage of high efficiency is that less power is wasted as heat -- this means a cooler PSU that requires less airflow to maintain safe operating temps: read - quieter.

Power Factor (PF). This measurement can be read directly off the Kill-A-Watt. In simple terms, it tell us how much AC power is lost to harmonics (unnecessary electromagnetic energy) while driving the PSU. PF is a property that varies somewhat depending on load. The ideal PF is 1.0. which means no AC power is lost. A PF of 0.5 means that to deliver 100W in AC to a PSU, your electric company actually uses 200W and this is most definitely shown in your electric bill.. 100W is lost or wasted. Active PF Correction (PFC) power supplies usually have a PF of >0.95. Passive PFC units usually run 0.6 - 0.8. Non-PFC units usually measure 0.5-0.7.

PF is not significant in terms of noise, heat or performance for a PC, but it is very relevant to real electricity consumption and energy conservation. Here is a simple illustration of worst and best case scenarios based on real tests I conducted on real PSUs (not published): A non-PFC low efficiency PSU vs an Active-PFC high-efficiency PSU.

64% efficiency/ 0.5 PF PSU
78% efficiency / 0.99 PF PSU
DC power delivered
AC power delivered
Lost as heat in AC/DC conversion
Total AC power used*
AC power lost to harmonics
Total power wasted

*Total AC power used: This is what your electric bill would be based on, assuming you drove your PSU to 300W steady DC output, which is unlikely.

As you can see, the differences are remarkable, especially the bottom figures. If you are running large numbers of PCs, there's absolutely no question of the benefits of high PFC and, to a lesser degree, high efficiency.

The Heath / Zenith SM-2320 multimeter, a fairly standard unit, is used to measure fan output voltages and the line voltages of the PSU output. The latter is done via the terminal pin on the front panel, above the connections for the DC outputs from the PSU.

The Test Lab is a spare kitchen measuring 12 by 10 feet, with an 8 foot ceiling and vinyl tile floors. The acoustics are very lively and allows even very soft noises to be heard easily. The PSU under test is placed on a piece of soft foam to prevent transfer of vibrations to the table top. Temperature in the lab is usually 20C or slightly lower. This is something of a problem as PSUs usually operate in environments that easily reach 45C. Sited next to or above the CPU, the PSU is always subject to external heat. This brings us to the next topic...

In-case Thermal Simulation

The solution is a 100W AC bulb in an empty case with the PSU mounted normally. The distance between the bottom of the PSU and the top of the bulb is about 7 inches. All the case back panel holes are blocked with duct tape. The only significant exit for the hot air in the closed case is the PSU, which is then subject to a fair amount of heat, probably a bit more than would be seen by a PSU in a real case because there are usually other air exits. The bottom front panel case intake hole is very large. In testing, the front of the case is moved so it hangs over the edge of desk, over free air, to ensure good fresh convection airflow. There are no case fans.

A thermistor taped to the bottom of the PSU close to its right front is used to monitor temperature. It's the little blue nub hanging down off the black wire in the photo above. Its temperature is somewhat affected by the airflow of the PSU fans but not directly in the airflow path.

The simulation means the PSU must cope with the 100W of heat generated by the light bulb plus whatever heat it generates within itself. It is a good simulation when the PSU is actually putting out >100W of DC voltage, although in real-life systems, there would be other air exhausts paths, resulting in a bit lower case temperature. So call it a very demanding test.

No PSU Temperature Measurements are done. Some previous PSU reviews here at SPCR featured temp measurements, meant to provide a more complete picture of performance. Discussions in the SPCR forums have convinced me that there are far too many variables at play to make internal PSU temperature a reliable gauge of... anything. There are way too many ways to interpret the numbers. Check this thread for the full discussion. The most critical parameter for thermal performance is AC-to-DC conversion efficiency. If efficiency is high, the size of the heatsinks and vent openings large, and the fan can blow a lot of air at full power, then excellent cooling is ensured.

Noise Measurements

The Heath AD-1308 is a portable half-octave Real Time Spectrum Analyzer with sound level meter (SLM) functions. Below 40 dBA, its accuracy is poor, limited to 3 dB increments, down to 23 dBA. Some 15 years old, this LED-based unit has long since been displaced by digital devices with better interfaces to PCs. The "A" weighting was used; it most closely approximates the frequency response characteristics of human hearing.

The microphone on the sound meter is positioned within an inch to the side of the PSU fan exhaust to avoid fan turbulence in the microphone itself. The dBA obtained here cannot be compared to any other measurements due to the lack of adherence to a repeatable standard and the uncontrolled reflective environment.

The noise measurements are always accompanied by descriptions of subjective perceptions. Without these, the measurements, which are not that reliable, provide only part of the picture.

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