Nexus RX-8500 850W Power Supply

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TEST RESULTS

Ambient conditions during testing were 23°C and 11 dBA. AC input was 118~122V, 60Hz. .

OUTPUT & EFFICIENCY: Nexus RX-8500
DC Output Voltage (V) + Current (A)
Total DC Output
AC Input
Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.10
0.96
-
-
4.98
0.95
3.40
0.96
0.1
0.1
21.3
39
54.7%
12.10
0.97
12.10
1.69
4.98
0.96
3.38
0.97
0.1
0.1
41.9
63
66.5%
12.10
1.87
12.10
1.69
4.98
1.88
3.37
2.68
0.2
0.4
63.7
89
71.6%
12.13
1.87
12.13
3.37
4.98
2.79
3.37
2.63
0.2
0.4
88.9
118
75.4%
12.14
3.76
12.13
4.91
4.98
5.41
3.37
4.62
0.3
0.5
150.4
188
80.0%
12.20
4.76
12.20
6.58
4.96
6.03
3.35
7.16
0.3
1.2
202.3
244
82.9%
12.29
7.62
12.28
6.71
4.96
7.84
3.35
8.02
0.4
1.4
251.6
303
83.6%
12.30
7.68
12.30
9.73
4.95
7.74
3.34
9.22
0.5
1.4
303.5
362
83.8%
12.35
11.47
12.34
11.43
4.95
12.35
3.31
12.24
0.5
1.5
400.2
477
83.9%
12.40
16.20
12.39
13.10
4.93
15.93
3.27
15.10
0.5
1.5
505.7
614
82.4%
12.45
16.20
12.44
25.80
4.91
18.20
3.23
19.72
0.8
1.5
701.5
885
79.3%
12.47
24.91
12.47
29.10
4.88
18.66
3.19
19.12
0.8
1.5
849.4
1092
77.8%
Crossload Test
12.38
21.70
12.38
23.4
5.21
0.97
3.32
0.96
0.1
0.1
666.3
804
82.9%
+12V Ripple: 87mV max @ 850W
+5V Ripple: 31mV max @ 850W
+3.3V Ripple: 27mV max @ 850W
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.

OTHER DATA: Nexus RX-8500
Target Output (W)
20
40
65
90
150
200
250
300
400
505
700
850
Intake (°C)
23
25
26
27
30
32
33
34
34
39
43
44
Exhaust (°C)
25
27
31
32
36
39
42
44
48
54
65
72
Temp Rise (°C)
2
2
3
6
7
7
9
10
14
15
22
32
Fan
not available*
SPL (dBA@1m)
14
14
14
14
14
18
23
28
32
32
33
33
Power Factor
0.83
0.95
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
AC Power in Standby: 0.9W
AC Power with no load: 10.8W
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.


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.

Various VAC Inputs: M700W @400W Output
VAC
AC Power
Efficiency
245V
716W
83.8%
120V
742W
81.0%
110V
752W
79.8%
100V
766W
78.4%

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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