Stress Test: Power Supplies Under Full Load

AcBel ATX-550CA -AB8FM: Failure - But 10-Year Warranty

The 550 watt Acbel did not make it through the test. Nonetheless, the manufacturer offers a 10-year warranty - probably a new record.

The graphic above shows the power supply connections and their length in centimeters. The AcBel has sufficient connections. There is no second connection for another graphics card in SLI operation.


Behind the cryptic product description ATX-550CA-AB8FM, which could only have been created by engineers, is a well-made power supply unit from the 550 watts class. It is equipped with a 120 mm cooling fan and the reflective outer surface is painted gray. However, the unit is not completely user-friendly: an adapter is necessary for SLI operation of graphics cards. On the other hand, AcBel already has an 8 pin voltage connector for dual-core processors. On the down side, the ambitious user will miss pluggable leads, making cable spaghetti a problem when it comes to cooling or getting a good overview of what's in the PC housing. In view of the product's sample status, we can excuse the fact that it is equipped with a non-divisible 24 pin ATX-connector. Here, you have to buy an adapter for most systems so that the power supply unit can even be used.

The AcBel 550CA with 550 watts is now ready to go

The AcBel 550CA operating in the dark.

Identification plate with power ratings.

Test Results

Already after the first few hours of operation it became clear that the power supply unit from AcBel could not keep up its voltages in accordance with ATX specifications. The 3.3 volts cable collapsed under maximum load at 3.09 volts, which in practice could lead to a system crash.

Input: 716 watts (209 volts, 3.46 ampere, cosphi 0.99)

Output: 550 watts (26.4 ampere/3.3 volts, 20.0 ampere/5 volts and twice 15.0 ampere on 12 Volt, 20 watts on -5/-12 volts, 5 volts standby)

Efficiency at maximum load: 76.8 percent (166 watts dissipation increases the air temperature by just under 7° Celsius

Noise reading at maximum load: 61.1 dB(A) in 4.72 inch (12 cm) gaps

Storage oscillo-scope: Here it shows that on the 3.3 volts cable a fluctuation of 40 mV and for the 12 volts string a difference of 70 mV occurs. This is all within the specifications.

For the first 12 volts cable it's 12.09 volts, for the second 12 volts voltage (CPU) it's 11.99 volts, for the 5 volts cable it's 4.76 volts and for the 3.3 volts cable it's 3.09 volts. The specification defines 3.14 volts as lower limit.

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AcBel ATX-550CA-AB8FM (550 watts)
Test Phase 1
Test DescriptionLower LimitUpper LimitResult
Increase load from 20% to 100% of nominal load limit110 watts550 wattsPassed
Test Phase 2
Test DescriptionRow 4 - Cell 1 LoadResult
Steady load at 100% nominal loadRow 5 - Cell 1 550 wattsPassed
Test Phase 3
Voltage Stability
Power RailMeasurementMin/Max according to ATX Spec.Result
+ 3.3 V+ 3.09 V+/- 5% (+3.14 to +3.46 V)Failed