SilverStone SFX Series SX700-LPT PSU Review

Transient Response Tests

Advanced Transient Response Tests

For details on our transient response testing, please click here.

Ιn these tests, we monitor the SX700-LPT's response in two different scenarios. First, a transient load (10A at +12V, 5A at 5V, 5A at 3.3V, and 0.5A at 5VSB) is applied for 200ms while the PSU works at 20 percent load. In the second scenario, the SX700-LPT is hit by the same transient load while operating at 50 percent load. In both tests, we use our oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.

These tests are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100 percent load of CPU/GPUs). We call these tests "Advanced Transient Response Tests," and they are designed to be very tough to master, especially for a PSU with a capacity of less than 500W.  

Advanced Transient Response at 20 Percent

VoltageBeforeAfterChangePass/Fail
12V12.199V12.066V1.09%Pass
5V5.051V4.915V2.69%Pass
3.3V3.359V3.232V3.78%Pass
5VSB5.016V4.898V2.35%Pass

Advanced Transient Response at 50 Percent

VoltageBeforeAfterChangePass/Fail
12V12.159V12.035V1.02%Pass
5V5.019V4.898V2.41%Pass
3.3V3.343V3.207V4.07%Pass
5VSB4.970V4.876V1.89%Pass

The response of the +12V rail is good for this form factor's standards, since both deviations barely exceed 1%. In addition, even while the transient load is applied, the voltage on this rail stays above 12V. Deviations are pretty high on the 5V and 5VSB rails, while we measure the highest voltage drops at 3.3V, as usual.

Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:

Transient Response At 20 Percent Load

Transient Response At 50 Percent Load

Turn-On Transient Tests

In the next set of tests, we measured the PSU's response in simpler transient load scenarios—during its power-on phase.

For the first measurement, we turned the SX700-LPT off, dialed in the maximum current the 5VSB could output, and switched the PSU on. In the second test, we dialed the maximum load the +12V could handle and started the SX700-LPT while it was in standby mode. In the last test, while the PSU was completely switched off, we dialed the maximum load the +12V rail could handle before switching the PSU on from the loader and restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12 V is 13.2 V, and 5.5 V for 5 V).    

All slopes are perfect without even a hint of a voltage spike or overshoot. SilverStone demonstrates very good performance.

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4 comments
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  • JQB45
    Overpriced
  • powernod
    Purely disappointing!!.
    A permanent flaw (false power-good signal), combined with a periodical flaw (far out of specs ripple if this unit gets overloaded), are more than enough evidence in order for me to conclude that this PSU is a potential danger for the rest of the hardware!!.
    Once more, thanks for the great review Aris!
  • basroil
    I looked at the internals first, and from that assumed this thing would be an utter mess. Surprisingly it's only a mess... If it was rated as a 550W unit I would have just said the holdup time was disappointing, but as a 700W rated unit this thing goes in the junk list.

    And seriously, what were they thinking with that layout? One short and the thing will definitely fry and take down your circuit breaker with it. Considering the number of missed surface mount solder points, shorts are going to be likely.
  • gadgety
    Great review. Thank you.