One of the first things we want to see is how well this PSU can regulate the DC outputs and maintain stable voltages.  To simulate real world and maximum loading conditions, the SilverStone Element ST70EF 700W PSU was connected to the load testers and supplied with a constant 115 VAC.  In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads.

The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs.  I have also included a second table of expanded tolerances (±1% to ±6%) for reference.

The following tables list the DC voltage results for the PSU while operating on 115 VAC, 60 Hz.  Note: the five +12V outputs where combined to four DC programmable loads for testing.

The PSU produced excellent load regulation on all of the outputs across a broad range of loads; even when delivering the maximum rated capacity of 700 watts DC power.

•    +3.3V         (3.35 to 3.25)            +2% to -2%
•    +5V           (5.07 to 5.02)            +2% to -0%
•    +12V1        (12.06 to 11.94)        +1% to -1%
•    +12V2        (12.06 to 11.91)        +1% to -1%
•    +12V3        (12.06 to 11.90)        +1% to -1%
•    +12V4        (12.06 to 11.89)        +1% to -1%
•    -12V          (-11.93 to -12.00)      +1% to -0%
•    +5VSB        (5.03 to 4.94)            +1% to -2%

All of the outputs stayed within ±2% regulation and the +12V outputs stayed within ±1% (even when delivering the max 56A combined load), which is outstanding!

DC Output Line Regulation

In this test we are interested in seeing how well a PSU can maintain the various output voltages while the AC input line voltage changes.  In the previous Load Regulation test, the AC line voltage was held constant at 115 VAC.  Now we will look at how much the DC outputs change as the load is held constant and the AC line voltage is changed from 120 VAC down to 90 VAC.

The Line Regulation test was performed with the combined DC loads set to 525W.  The AC input voltage to the power supply (via the Extech power analyzer) was adjusted using a Powerstat variable autotransformer.  We observed virtually no measurable change in the DC outputs; again very good.