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TEST RESULTS
Ambient conditions during testing were 23°C and 11 dBA. AC input was 118~122V,
60Hz. .
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OUTPUT & EFFICIENCY: Nexus RX-8500
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DC Output Voltage (V) + Current (A)
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Total DC Output
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AC Input
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Calculated Efficiency
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+12V1
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+12V2
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+5V
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+3.3V
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-12V
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+5VSB
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12.10
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0.96
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-
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-
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4.98
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0.95
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3.40
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0.96
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0.1
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0.1
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21.3
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39
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54.7%
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12.10
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0.97
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12.10
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1.69
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4.98
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0.96
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3.38
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0.97
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0.1
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0.1
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41.9
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63
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66.5%
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12.10
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1.87
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12.10
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1.69
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4.98
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1.88
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3.37
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2.68
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0.2
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0.4
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63.7
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89
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71.6%
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12.13
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1.87
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12.13
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3.37
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4.98
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2.79
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3.37
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2.63
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0.2
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0.4
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88.9
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118
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75.4%
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12.14
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3.76
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12.13
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4.91
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4.98
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5.41
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3.37
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4.62
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0.3
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0.5
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150.4
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188
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80.0%
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12.20
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4.76
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12.20
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6.58
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4.96
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6.03
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3.35
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7.16
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0.3
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1.2
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202.3
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244
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82.9%
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12.29
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7.62
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12.28
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6.71
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4.96
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7.84
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3.35
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8.02
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0.4
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1.4
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251.6
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303
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83.6%
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12.30
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7.68
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12.30
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9.73
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4.95
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7.74
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3.34
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9.22
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0.5
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1.4
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303.5
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362
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83.8%
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12.35
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11.47
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12.34
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11.43
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4.95
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12.35
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3.31
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12.24
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0.5
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1.5
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400.2
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477
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83.9%
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12.40
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16.20
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12.39
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13.10
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4.93
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15.93
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3.27
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15.10
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0.5
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1.5
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505.7
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614
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82.4%
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12.45
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16.20
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12.44
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25.80
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4.91
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18.20
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3.23
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19.72
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0.8
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1.5
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701.5
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885
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79.3%
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12.47
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24.91
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12.47
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29.10
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4.88
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18.66
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3.19
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19.12
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0.8
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1.5
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849.4
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1092
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77.8%
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Crossload Test
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12.38
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21.70
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12.38
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23.4
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5.21
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0.97
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3.32
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0.96
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0.1
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0.1
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666.3
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804
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82.9%
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+12V Ripple: 87mV max @ 850W
+5V Ripple: 31mV max @ 850W
+3.3V Ripple: 27mV max @ 850W
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NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings of the DBS-2100
PS Loader. It is a tiny portion of the total, and potential errors arising
from inaccuracies on these lines is <1W.
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OTHER DATA: Nexus RX-8500
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Target Output (W)
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20
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40
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65
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90
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150
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200
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250
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300
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400
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505
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700
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850
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Intake (°C)
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23
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25
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26
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27
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30
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32
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33
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34
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34
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39
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43
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44
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Exhaust (°C)
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25
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27
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31
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32
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36
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39
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42
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44
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48
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54
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65
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72
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Temp Rise (°C)
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2
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2
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3
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6
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7
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7
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9
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10
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14
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15
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22
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32
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| Fan |
not available*
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| SPL (dBA@1m) |
14
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14
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14
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14
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14
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18
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23
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28
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32
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32
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33
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33
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Power Factor
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0.83
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0.95
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0.99
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0.99
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0.99
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0.99
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0.99
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0.99
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0.99
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0.99
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0.99
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0.99
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AC Power in Standby: 0.9W
AC Power with no load: 10.8W
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NOTE: The ambient room temperature during
testing can vary a few degrees from review to review. Please take this
into account when comparing PSU test data.
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ANALYSIS
1. EFFICIENCY — This is a measure of AC-to-DC
conversion efficiency. The ATX12V v2.2 Power Supply Design Guide recommends 80% efficiency
or better at all output power loads. 80% efficiency
means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost
as heat within the PSU. Higher efficiency is preferred for reduced energy consumption
and cooler operation. It allows reduced cooling airflow, which translates
to lower noise.
The RX-8500 does not reach 80% efficiency until 150W load, which is about 17% of rated power. This is good enough for 80 Plus performance, but it's still a high level of power for 80% efficiency, especially when efficiency is so much worse at lower levels. The fact is that most systems will idle at lower than 150W unless it's really a beast of a gaming system. The mediocre lower power efficiency is left behind as output rises above 150W, and the unit achieves a relatively high plateau of >82% efficiency from 200~500W. Above that power output, efficiency falls again as expected in the face of rising temperature. The drop to below 78% efficiency is not unusual; it's surprising to see it hold up as high.
2. VOLTAGE REGULATION refers to how stable the output voltages
are under various load conditions. The ATX12V Power Supply Design Guide calls
for the +12, +5V and +3.3V lines to be maintained within ±5%.
The lower 5V and 3.3V lines were very stable under all but the most severe loads. The 12V line actually climbed as load increased, to a high of 12.45V at very high loads. This oddity should not be too much of a concern; it's still within the 5% recommended variance for the 12V line. Voltage regulation in the crossload test was fine.
3. AC RIPPLE refers to unwanted "noise"
artifacts in the DC output of a switching power supply. It's usually very high
in frequency (in the order of 100s of kHz). The peak-to-peak value is measured.
The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V
line and 50mV on the +5V and +3.3V lines.
Ripple was good, but not exceptional as the load increased. The 87mV peak on the 12V line was within the 120mV maximum allowable, and the 5V and 3.3V lines were under the 50mV maximum at worst loads.
4. POWER FACTOR is ideal when it measures 1.0. In the most
practical sense, PF is a measure of how "difficult" it is for the
electric utility to deliver the AC power into your power supply. High PF reduces
the AC current draw, which reduces stress on the electric wiring in your home
(and elsewhere up the line). It also means you can do with a smaller, cheaper
UPS backup; they are priced according to their VA (volt-ampere) rating. PF on our sample was poor at the lowest (and somewhat unrealistic) loads but improved to nearlt 0.9 by about 65W load. Near 1.0 performance was reached above 400W load.
5. LOW LOAD PERFORMANCE is significant mainly to minimize energy waste and with system that demand very low power; the latter can cause some PSUs not to start. Standby performance was fine with 0.9W draw. The unit powered up with no load, drawing about 11W, suggesting it has a built in loader to prevent low loads from causing trouble.
6. CROSSLOAD TEST - Basically the load on the 12V line was maximized while the load on all the other lines was minimized. Voltage regulation on all the lines was good, and ripple stayed well limits. There were no other changes.
7. 240 VAC INPUT - The power supply was set to 600W load with 120VAC through the
hefty variac in the lab. The variac was then dialed 10V lower every 5 minutes.
This is to check the stability of the PSU under brownout conditions where the
AC line voltage drops from the 110~120V norm. Most power supplies achieve higher efficiency
with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, which
was used to check power supply efficiency for the benefit of those who live
in 240VAC mains regions.
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Various VAC Inputs: M700W @400W Output
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VAC
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AC Power
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Efficiency
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245V
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716W
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83.8%
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120V
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742W
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81.0%
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110V
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752W
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79.8%
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100V
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766W
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78.4%
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There were no surprises here. Our sample's efficiency improved by nearly 3% at the higher VAC, and dropped a little over 1% for each 10V drop in VAC. Voltage regulation and ripple were unchanged.
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