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Fortron FSP350-60PN "Aurora" 120mm fan PSU

August 25, 2003 -- by Mike Chin

Product "Aurora" 350W ATX12V Power Supply

FSP350-60PN / LED Fan / non-PFC
Manufacturer/ Supplier Fortron-Source
Typical Price US$55

Fortron-Source meant for this power supply to be seen. Blue is the LED color of cool in the past year, and blue is the color of LED light that glows over the big 120mm fan in this new ATX12V power supply. In a dimmed room within one of those snazzy windowed cases -- or maybe a transparent acrylic one -- this power supply unit could certainly bring a high level of cool to its owner.

In the light of day, the Fortron-Source PSU still looks unusual for a number of reasons:

- First there is the translucent LED-equipped 120mm fan already mentioned. It is big. It is installed in the only place a fan this size can be in an ATX form factor power supply -- on the side that in a tower case would be facing the CPU.

- Then there is the slivery finish, which is somewhat like aluminum but not quite. In fact, it is nickel-plating, said to be for anti-corrosion, but don't you believe that for a minute! When was the last time you saw rust or oxidation disfiguring your PSU? (And why would you really care?) No, the only function that can really be ascribed to the nickel-plating finish is cosmetic.

- Thirdly, a vast array of hexagonal holes on the outward-facing panel for excellent airflow and a real transparent look.

- Finally, it has a fan speed control knob. This is not that unusual, but not an everyday thing either.

Like many of the other PSU makers, Fortron-Source is getting savvy to the idea of merchandising. The retail box is attractive (more blue!), and makes many statements including:

  • Super Quiet
  • Anti-Corrosive nickel-plated casing
  • Near silent illuminated 12cm fan
  • Variable airflow control for improved system cooling
  • Intel ATX12V Compatible
  • Complete output protection
  • Maximum output of 400W (It's not clear what this refers to.)
  • Meets international safety standards
  • Supports Pentium 4 at 3GHz and AMD XP CPUs

An owner's manual is included, along with a power cord and 4 mounting screws.

One illustration in the manual provides an AMD-approved technical airflow / cooling reason for the 120mm fan configuration of this PSU. A couple of years ago, in one of their guides for system builders, AMD did endorse the concept of a fan on the PSU panel facing the CPU in a tower case for improved cooling. However that document never actually defined the more conventional airflow path as being "undesirable".

Output Specifications

AC Input
120/240 VAC, 50-60 Hz
DC Output
+3.3V
+5V
+12V
-12V
-5V
+5VSB
Load Regulation
-/+5%
-/+5%
-/+5%
-/+10%
-/+10%
-/+5%
Line Regulation
-/+1%
-/+1%
-/+1%
-/+2%
-/+2%
-/+1%
Min Load (A)
0.3
0.1
0
0
0
0
Normal Load (A)
14
12.7
4.5
0.4
0.15
1.0
Max Load* (A)
21.2 / 28
25.5 / 30
16
0.8
0.3
2.0
Max Power
220W
192W
9.6W
1.5W
10W
Max Power
350W? (not clearly specified)

*When +3.3V load is 28A, the +5V maximum load is 25.5A. When +3.3V load is 21.2A the +5V maximum load is 30A.

Note that there are several options for the Fortron-Source 120mm fan PSUs. It amounts to 4 variants for each power model for a total of 8 variants. It's not clear whether all 8 variants are available.

Power
Fan
PFC*
300W
LED
Passive
350W
no LED
non

*Power Factor Correction: See explanation in test methodology section.

There are also versions of the 120mm fan Fortron-Source PSU without a manual fan speed control knob. Potentially, that adds another 8 variants to the product mix.

Discussions in the SPCR PSU Forum about these Fortron-Source 120mm fan PSUs have suggested that the variants with PFC are equipped with a more aggressive fan speed control circuit that boosts the fan speed at lower temperature than the non-PFC variants, making the PFC equipped models noisier than the non-PFC models. This cannot be confirmed without further testing and comparison against a non-PFC version of the same power rating.

MORE PHYSICAL DETAILS

The first photo below shows the inside panel, which has hardly any vents at all. This ensures that the air that the fan blows in is vented out the back to the outside of the case.

The photos with the cover removed show aluminum heatsinks that are quite small -- presumably to make room for the large fan:

There is additional circuitry on two smaller PCBs. One of these is clearly a fan control circuit board. This is the one attached to one of the heatsinks. The little black block next to it on the heatsink is the thermistor, which is screwed and hot-glued to the HS.

The output capacitors on this board are relatively small, like the heatsinks. They had to be short enough to make room the for 1" depth of the 120mm fan. The unpopulated portion of the printed circuit board by the capacitors is unusual, compared to the many other already seen that were OEM'ed by Fortron-Source. On most of those, there is no bare space on the board at all. Whether this lower PCB parts density means anything is not a question easily answered.

Connectors

There are a total of 6 wire sets:

  • 32" long cable with two 4-pin IDE drive connectors and one floppy drive power connector
  • 24" long cable with one 4-pin IDE drive connector and one floppy drive power connector
  • 24" long cable with two 4-pin IDE drive connectors
  • 21" long cable for main 20-pin ATX connector
  • 21" long cable for dual 12V (P4) connector
  • 21" long cable for 3.3V connector

TEST METHODOLOGY

Parameters Tools
DC load on PSU DBS-2100 PSU load tester
Ambient temperature
Any number of thermometers
Fan / DC voltage regulation
Heath / Zenith SM-2320 multimeter
AC power
Kill-A-Watt Power Meter
Noise
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 hooked up to the load tester. This ensures that the current delivered is distributed to as many short leads as possible. When pushing a PSU to its rated output, the heat generated in the wires can be an issue.

The PSU is tested at 5 DC output power levels:

  1. 65W: A very typical DC power draw by many system at low / modest load.
  2. 90W: Established previously as a typical max power draw of a mid-range desktop PC.
  3. 150W: For higher power machines.
  4. Maximum (350W) The usual 300W test was left off because it is so close to the max.

Care is taken to ensure that the load on each of the voltage lines does not exceed the ratings for the PSU. The PSU is left running 5~10 minutes at each power level before measurements are recorded.

The DBS-2100 is equipped with 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 an 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% power load. 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. In practical technical terms, it is the difference between the measured V(oltage) x A(mperes) and AC power in Watts. PF 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 often shown in your electric bill as savings (depends on your electric utility company and your account with them). 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 relevant to electricity consumption and energy conservation. 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 digital display multimeter, a fairly standard unit, is used to measure the fan 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. 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 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. Still, 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. This is probably more heat than would be seen by a normal PSU, because in a real case, there are usually other air exits, and at least one case fan.

A 60W bulb is used for the 65W and 90W load tests; it seems a more realistic heat source for those lower power loads. The higher power tests use a 100W bulb.

The PSU must cope with the heat generated by the light bulb plus whatever heat it generates within itself. In real systems, there would be other air exhausts paths, and mostly likely at least one case fan. So a Panaflo 80mm Low speed fan is mounted on the back panel of the test case and connected to a voltage controller. The PSU is run through its load range with and without the fan turned on, to 7V, which is about the level at which most PC silencers would run their case fan. It is a reasonable low noise PC simulation.

Noise Measurements

For this review, I used a highly accurate calibrated B&K model 1613 sound level meter on temporary loan from the University of BC's acoustics lab.

This professional caliber SLM dates back to 1978, weighs over 10 pounds, and is completely analog in design. It has a dynamic range that spans over 140 dB. The microphone used has a 1" diaphragm that's very responsive to low sound levels and low frequencies. The unit's absolute sensitivity reaches below 0 dBA -- at one point in the midband (1kHz) I was seeing -4 dBA for background noise in the UBC anechoic chamber.

Noise readings were taken with the microphone positioned at 1 meter distance, facing the control panel. The ambient noise level in the live test room was ~16 dBA.

Being done at 1 meter distance, the noise measurements are somewhat comparable to manufacturers' specs. Note, however, that differences in the temperature of the test conditions, and the fact that these measurements were made in a live room rather than an anechoic chamber, makes such comparisons not quite valid, either. Because of the higher background noise level in the live test room, and the high degree of reflections from boundaries (walls, ceiling, floor), these measurements generally run higher than they would be in an anechoic chamber.

As usual, noise measurements are accompanied by descriptions of subjective perceptions. The measurements provide only part of the picture.

TEST RESULTS

Measurements were made at 5 output power levels: 65W, 90W, 150W, and 350W. The PSU was allowed to run for 10~15 minutes at each power level before measurements were recorded. The room temperature was 24C.

A. Load on the PSU

DC LOAD
65W
90W
150W
350W
+12V
24
36
60
156
+5V
20
20
40
110
+3.3V
16.5
26.4
42.3
78
-12V
2.4
3.6
3.6
3.6
-5V
1
2
2
1
+5VSR
1
2
2
1

B. On test bench, in 24C ambient temperature

AC Power
105W
137
217
533
Efficiency
62%
66%
69%
65%
Power Factor
0.62
0.67
0.68
0.71
Fan Voltage (min-max)
3.9-9.7 V
4.1-10.4 V
4.2-10.7 V
9.5-11.2 V
Noise (min-max)
24-42 dBA
24-44 dBA
25-45 dBA
42-45 dBA

The range of the manual fan speed controller is tied to the internal thermistor. When the load and/or temperature is high, the minimum speed available goes up. Note that at 65W output, the minimum fan voltage is 3.9V while at maximum power output, the minimum fan speed is 9.5V. The maximum speed available also goes up, but not as dramatically.

C. In thermal simulation case, over light bulb, no case fan

DC LOAD
65W
90W
150W
350W
AC Power
107W
137
218
533
Efficiency
61%
66%
69%
65%
Light bulb
60W
60W
100W
100W
Fan Voltage (min-max)
4.1-10.7 V
4.2-10.7 V
6.9-10.8 V
10.8-11.3 V
Noise (min-max)
24-42 dBA
24-44 dBA
31-45 dBA
42-45 dBA
Case Temp (min-max)
30C - 28C
30C - 38C
32C - 32C
33C - 32C
Exhaust °C (min-max)
34C - 32C
34C - 32C
37C - 34C
40C - 34C

ANALYSIS

1. VOLTAGE REGULATION was good, within -/+2% on all lines in any combination of loads. The low and high voltage seen on each of the main lines is shown:

  • +12V: 11.85 to 12.42
  • +5V: 4.92 to 5.27
  • +3.3V: 3.34 to 3.41

We have no way of testing line regulation, so AC conditions are steady-state, not dynamic as it would be (potentially) in a real PC. The AC input as measured by Kill-a-Watt is usually within a couple of volts of 120V.

2. EFFICIENCY was modest throughout the power load range and never reached 70% even at high loads. This is below average performance compared to all other PSUs tested by SPCR. One thing to note here is that the power conversion efficiency at 350W is substantially lower than at 150W. This suggests that at 350W output, the PSU is already operating at beyond its maximum; normally, efficiency is highest at or just below maximum output, then falls off beyond.

3. POWER FACTOR was mediocre, ranging from a low of .62 at low loads to a high of .71 at maximum power load. This was expected, given the absence of any power factor correction.

4. FAN VOLTAGE: The fan receives full voltage (10-11V) for a couple of seconds upon startup to ensure that it always starts even if set to the minimum speed, which is a low 3.9V. Although, as mentioned earlier, the fan speed is affected by the internal temperature of the PSU, the minimum speed stays fairly close to 4V except at high power output load. This is particularly true when the PSU is operated on the test bench out of the case.

In the case with the thermal simulation of the light bulb, the first significant change comes at the 150W output level with the 100W bulb. The minimum fan voltage jumps from 4.2V (without external heat) to 6.9V. At this speed the fan is plainly audible, though without any annoying high pitch. At full power, there is virtually no difference between min & max settings of the fan speed dial -- both are very close to the maximum voltage of 11.3V.

5. NOISE was measured at 1 meter from the exhaust grill. The test environment is live, so readings are higher than would be obtained in an anechoic chamber readings. (See explanation in Test Methodology section above.)

Subjectively, the Aurora PSU is quiet. The 120mm fan has a lower pitch sound than most 80mm fans and spins very slowly at minimum. It has some ticking bearing noise, and hums rather than buzzes. It measures and sounds a bit louder than the quietest 80mm fan PSUs tested previously. At the highest speed, wind turbulence noise dominates, along with humming that is higher pitch than at low speed.

The measured noise at minimum is a couple dBA higher than the last PSU tested, the Seasonic Super Silencer 400. It is 4 dBA noisier than a Nexus NX3000. Both of these are 80mm fan models.

6. THERMAL IN-CASE SIMULATION results are quite complex and deserve close attention. Note that the last 4 measured parameters -- fan voltage, noise, case temperature and PSU exhaust temperature -- all have minimum and maximum measurements. This relates to the setting of the manual fan control. The min figures refer to the parameter with the manual fan control at minimum; max is for the same measurement with the manual fan control at maximum.

The temperature of the case was monitored with a thermal probe positioned about 1" below the PSU intake vent and about 1" away from the center. The temperature of the exhaust air from the PSU was measured with a thermal probe positioned about 1/2" away from the center of the PSU exhaust grill panel.

Judging from the upturn in minimum fan speed at the 150W output level with the 100W bulb, in order to minimize noise from a system using this PSU, it is best to keep total system power draw to under 150W. This is not difficult to do with a mid-range system, one with a CPU rated to ~2.5 GHz, no more than a couple of hard drives and a mid-line video card. It is probably possible to run such a system without a case fan, with just the fan in the PSU at minimum and with a quiet fan on the CPU heatsink. Once the load reaches 150W, however, the min fan speed jumps to ~7V and the minimum fan noise reaches above 30 dBA at 1 meter.

7. WHAT ABOUT WITH A CASE FAN?

At the 150W and 350W loads, measurements were repeated with a Panaflo 80mm low speed fan (FBA08A12L1A -- our reference) mounted on the back panel. There was some question about how this case fan would interact with the 120mm fan in the PSU. You will recall this illustration from the first page:

It's the "desirable airflow" pattern shown on the left that was simulated with the case fan blowing out at 12V. At the 150W power load, turning the exhaust case fan on had the immediate effect of increasing the minimum fan voltage from 7V to almost 8V, with a concomitant 2-3 dBA rise in noise. This implies that the temperature seen by the internal PSU thermistor increased.

Why this should have occurred is a bit of a mystery. The total airflow out from the CPU area of the case was increased, so the internal PSU temperature should not have risen; quite the contrary, it should have dropped.

Curiosity and wonder about airflow motivated me to flip the case fan around so that it was blowing outside air into the case. My instinct was that the air being moved out of the case by the 120mm PSU fan at 7V should be fairly close to that blown in by the Panaflo at 12V; perhaps the total airflow through the case would not be much changed from with just the PSU fan working, but there would be the advantage of cooler outside air being blown directly into the hottest area of the case.

The effect of making the back case fan blow in was immediate. Both case and exhaust temperatures dropped by a couple of degrees and there was no increase in the PSU's minimum fan speed.

The results of this back panel case fan flip / flop is tabulated below.

Power Load
150W
350W
Case Fan
Off
Exhaust
Intake
Off
Exhaust
Intake
Fan Voltage*
6.9 V
7.9 V
6.9 V
10.8 V
11.1 V
10.8 V
Noise
31 dBA
34 dBA
31 dBA
42 dBA
43 dBA
42 dBA
Case Temp
32C
33C
29C
33C
33C
32C
Exhaust °C
37C
38C
33C
39C
40C
34C

*The manual fan speed control was set to minimum; it was the internal thermistor than made changes in fan voltage and noise in this test.

It is not clear whether these results would be repeatable in a real system. I encourage owners and users of this Fortron and other similar 120mm fan PSUs to experiment with back case fan directionality and report their findings in the SPCR Forums.

CONCLUSION

The Fortron-Source Aurora 350W ATX12V FSP350-60PN / LED fan PSU is a viable entry to the growing roster of low-noise PC components. It invites experimentation with case airflow. Its strengths include

  • good looks, especially with blue LED fan
  • good stability and voltage regulation
  • good self-cooling
  • good directed airflow design
  • manual fan speed control and reduced noise

The Fortron-Source Aurora 350W does have a few weaknesses:

  • build quality does not seem as high as other Fortron-Source models
  • fan quality could be improved
  • noise could still be lower, especially at higher power loads

Our thanks to Fortron-Source for the Aurora 350W ATX12V FSP350-60PN / LED fan PSU review sample and for their kind support.

* * * * *

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