EnergyKnight SS-350ET-T3: the cheapest Seasonic unit (updated)

Load testing

Loading +5 V SB

As always, all load testing is done according to our testing methodology. The efficiency of this unit’s stand-by supply is just about average at 75 %. The ripple is very nice and voltage regulation is still within 3 % which corresponds with the mainstream price.

Output (W)	Load (A)	Voltage (V)/ ripple (mV)	Input (W)	Efficiency/power factor
0	0	5.052/3.520	0	—/0.010
12.05	2.40	5.021/4.880	16.03	75.2 %/0.520
16.81	3.36	5.009/6.000	22.31	75.3 %/0.559

+5 V SB ripple (left to right): 0 A; 2.40 A; 3.36 A

Hold-up time

As we can see on the oscilloscope screenshot, the hold-up time of the SS-350ET-T3 +12 V rail is 15.08 ms. This is reasonably high value considering the rather small input capacitor.

The hold-up time of the power good signal is much shorter though, only 11.80 ms, that is quite an extreme difference.

The +12V rail has no problem delivering output power when the input has been interrupted for such period of time though. So it will keep providing power well within spec until the PG signal drops and makes motherboard and connected HW shut down.

Combined loading

Combined loading was mostly OK for the Seasonic SS-350ET-T3. Firstly, let’s talk about the voltage regulation. As this is an ordinary group design, we expect the regulation to be mediocre at best. The results are nice, all the voltages were kept under 3 % which is our mainstream requirement, so the unit does not lose any points here. Both the line and load regulation are good.

Output power	Load/ voltage +5 V SB	Load/ voltage +3.3 V	Load/ voltage +5 V	Load/ voltage +12 V	Load/ voltage −12 V	Input power	Efficiency/ power factor
8.4 %/ 29.45 W	0 A/ 5.049 V	0.012 A/ 3.387 V	0.413 A/ 5.127 V	1.875 A/ 12.274 V	0.360 A/ −11.883 V	39.18 W	75.2 %/ 0.821
20 %/ 69.20 W	0.532 A/ 5.039 V	1.492 A/ 3.384 V	1.598 A/ 5.103 V	3.95 A/ 12.305 V	0.393 A/ −11.989 V	84.88 W	81.5 %/ 0.951
40 %/ 135.31 W	1.015 A/ 5.027 V	2.88 A/ 3.375 V	2.300 A/ 5.107 V	8.48 A/ 12.265 V	0.393 A/ −12.052 V	161.1 W	84.0 %/ 0.983
60 %/ 214.02 W	1.53 A/ 5.014 V	2.97 A/ 3.370 V	3.45 A/ 5.113 V	14.24 A/ 12.214 V	0.396 A/ −12.128 V	255.0 W	83.9 %/ 0.987
80 %/ 276.74 W	1.89 A/ 5.002 V	5.49 A/ 3.363 V	4.95 A/ 5.099 V	17.91 A/ 12.214 V	0.399 A/ −12.189 V	333.5 W	83.0 %/ 0.987
100 %/ 344.20 W	2.38 A/ 4.989 V	7.03 A/ 3.373 V	6.05 A/ 5.099 V	22.4 A/ 12.181 V	0.401 A/ −12.241 V	420.5 W	81.9 %/ 0.988

The efficiency is also nice. As usual, my instruments show some combined drift compared to results achieved with high-end load stations, but I believe the unit keeps the promissed 80 PLUS Bronze efficiency just OK.

Combined loading ripple

The ripple values of the SS-350ET-T3 are outstanding, especially for its price. The values are generally very low, only the +12 V rail ripple has somewhat risen by the end, but the unit still managed to keep it under 50 mV. It seems that Seasonic managed to make some nice progress with the new platform.

Output %	Ripple +5 V SB	Ripple +3.3 V	Ripple +5 V	Ripple +12 V	Ripple −12 V
8.4	8.000 mV	8.800 mV	10.00 mV	17.20 mV	20.40 mV
20	10.80 mV	7.200 mV	13.20 mV	24.80 mV	22.40 mV
40	11.20 mV	9.200 mV	13.200 mV	24.40 mV	21.20 mV
60	10.80 mV	12.00 mV	11.00 mV	25.60 mV	27.60 mV
80	12.20 mV	9.800 mV	11.40 mV	35.20 mV	22.80 mV
100	18.40 mV	17.60 mV	17.60 mV	49.90 mV	30.40 mV

Ripple 8.4% load (left to right): +5 V SB; +3.3 V; +5 V; −12 V. The second channel is connected to +12 V.

Ripple 100% load (left to right): +5 V SB; +3.3 V; +5 V; −12 V. The second channel is connected to +12 V.

Crossloading, overloading

Crossloading tests were not so good, as could be expected from such platform. Crossloading +3.3V and +12V rails was more or less OK, but the +5V rail showed the worst of this platform. As so often with many other units, crossloading this rail led to increase of the +12V rail voltage all the way out of the spec. As per ATX spec loading diagram, I have increased load from the rail, but the difference was minimal and so still out of spec. Clearly with such result, the unit cannot be allowed to pass.

Output power	Load/ voltage +5 V SB	Load/ voltage +3.3 V	Load/ voltage +5 V	Load/ voltage +12 V	Load/ voltage −12 V	Input power	Efficiency/ power factor
30 %/ 105.30 W	0.529 A/ 5.027 V	19.83 A/ 3.369 V	1.554 A/ 5.047 V	1.881 A/ 12.405 V	0.388 A/ −11.995 V	139.6 W	75.4 %/ 0.977
42 %/ 148.36 W	0.526 A/ 5.027 V	1.472 A/ 3.367	19.01 A/ 4.856 V	3.43 A/ 12.707 V	0.394 A/ −12.340 V	183.9 W	80.7 %/ 0.986
99 %/ 346.61 W	0.525A/ 5.018 V	1.464 A/ 3.362 V	1.629 A/ 5.207 V	27.20 A/ 11.969 V	0.414 A/ −12.124 V	415.2 W	83.5 %/ 0.988
116 %/ 407.68 W	3.30 A/ 4.969 V	4.15 A/ 3.351 V	3.15 A/ 4.721 V	32.7 A/ 10.739 V	0.361 A/ −11.146 V	509.1 W	79.0 %/ 0.989

The SS-350ET-T3 has no OCP capability so it was useless to even test that. The OPP implementation is quite the usual, there is limit of the power transferred from primary side. So the maximum I got from it was something between 400 and 450 W, before the voltage started to fall so low the power output decreased as well. Seasonic managed to achieve an absolute record of uselessness of secondary supervisor, which kicked in not sooner than when the +12 V voltage felt under 8.4 V. Using so low-end components with no independent +12 V UVP input obviously has some “unwanted effects”.

Crossloading, overloading ripple

The ripple is still very low, nice results.

Output %	Ripple +5 V SB	Ripple +3.3 V	Ripple +5 V	Ripple +12 V	Ripple −12 V
30	11.40 mV	8.600 mV	13.20 mV	25.60 mV	23.60 mV
42	9.200 mV	9.400 mV	11.20 mV	24.00 mV	22.40 mV
99	17.20 mV	14.80 mV	16.80 mV	34.40 mV	30.80 mV

Fan speed, temperatures and noise

The fan inside the Seasonic SS-350ET-T3 started spinning right away as soon as the unit was powered on. In the first three tests, it was running just at about 760 RPM, but then it increased quite fast to maximum speed, which is over 2100 RPM. It is already audible from the very minimum speed, but from test number four, it was already loud. At full load Seasonic managed to break its own record (Antec High Current Gamer M 750 W), the unit does not get that far away from turbofan engine.

Output %	Fan speed (RPM)	Temperature intake/ outtake	Noise (dBA)
8.4	749	22 °C/ 25 °C	39.4
20	760	21 °C/ 25 °C	39.4
40	773	21 °C/ 25 °C	39.4
60	1234	21 °C/ 27 °C	43.1
80	1905	23 °C/ 28 °C	49.6
100	2113	24 °C/ 27 °C	52.3
CL 30	1087	23 °C/ 30 °C	40.6
CL 42	1059	23 °C/ 27 °C	40.6
CL 99	2114	23 °C/ 27 °C	52.3
OL 116	1965	— °C/ — °C	49.7

The unit survived the Sweater contest fine, though it is no wonder. With such fan speed, the temperature difference between input and output is minimal so even putting it into a sweater did not change much. After removing the sweater again, outcoming temperature reached about 40 °C with speed of 2088 RPM. This may be to increase the lifespan of the bad capacitors in these units. And while for some time, OEM Seasonic units with bad caps were rare to find, lately I have seen a couple myself and also my customers demand all the time more capacitors to repair these very units. They do (almost always) survive the warranty though.

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