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Cooler Master MasterWatt 650 Power Supply Review

Last updated on January 24th, 2018 at 05:10 pm

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. We run at 35c in our environment to greater reflect warmer internal chassis conditions.

We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

We test in a single +12V configuration.

DC Output Load Regulation

Combined

DC Load

+3.3V
+5V
+12V
+5VSB
-12V
A
V
A
V
A
V
A
V
A V
65W
0.92
3.33
0.88
5.04
4.42
12.16
0.50
5.02
0.20
-12.03
130W
1.63
3.32
1.65
5.02
9.18
12.11
0.50
5.02
0.20
-12.03
325W
2.93
3.31
3.00
5.00
24.25
12.07
1.50
5.00
0.20
-12.03
490W
4.04
3.30
4.10
4.98
36.90
12.00
2.00
4.97
0.30
-12.02
650W
5.00
3.28
5.30
4.95
49.67
11.94
2.50
4.95
0.30
-12.01

Load regulation is pretty good, within 2.5%.

Cooler Master MasterWatt 650 Maximum Load
684 watts

We managed to get the PSU to deliver 684 watts before it would shut down, delivering around 34 watts more than the rated specifications.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing +3.3V +5V +12V -12V +5VSB
A V A V A V A V A V
590W 1.0 3.33 1.0 5.04 48.0 11.92 0.2 -12.00 0.50 5.01
145W 12.0 3.25 15.0 4.89 2.0 12.15 0.2 -12.01 0.50 4.98

The unit passed our cross load test. It was hit with 48A on the +12V rail and it held at 11.92.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum. ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output
Ripple (mV p-p)
+3.3V
50
+5V
50
+12V1
120
+12V2
120
-12V
120
+5VSB
50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load +3.3V +5V +12V 5VSB
152W 5 10 10 5
270W 10 10 20 5
400W 10 15 30 10
523W 15 20 40 15
650W 15 20 50 15

Ripple suppression is quite good, hitting 15mV and 20mV on the +3.3V and +5V rails respectively at full load. The +12V rail hit 50mV at full load, well within industry rated specifications.

Efficiency (%)
152W
86.3
270W
89.2
400W
88.7
523W
87.4
650W
86.6

Efficiency is pretty good for a 80 Plus Bronze unit, peaking at just over 89% and dropping to 86.6% at full load.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the Power Supply we have taken it into our acoustics room environment and have set our SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.

As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.

KitGuru noise guide

10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refrigerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
152W
<28.0
270W
<28.0
400W
31.5
523W
33.2
650W 34.9

Audio emissions are actually very impressive – with the power supply not really emitting noticeable noise until around 500 watts is demanded.

Temperature (c)
Intake
Exhaust
152W
36
41
270W
39
44
400W
42
49
523W
44
53
650W
47
62

At full load we measured temperatures around 62c.

Maximum load
Efficiency
684 watts
86

At 684 watts, the efficiency level measures 86%. Not a practical situation to be running 24/7, but worth noting.

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