Logisys PS350MA Power Supply Review
Load Tests
Contents
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
Because this is a very low-end power supply, we decided to run our tests a little differently. We tried to pull around 85 W on our first load pattern, around 100 W on our second load pattern, and from then on we increased our load pattern increments by 25 W until we discovered the maximum this unit would be able to deliver. As usual, we pulled more current/power from the +12 V outputs, as this better reflects the usage of a modern PC, since the CPU and the video cards are connected to these outputs. In the table below, we list the load patterns we used and the results for each load.
If you add all the powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, both inputs were connected to the power supply’s single +12 V rail.
| Input | Test 1 | Test 2 | Test 3 | Test 4 |
| +12VA | 3 A (36 W) | 3.5 A (42 W) | 4.5 A (54 W) | 5.5 A (66 W) |
| +12VB | 2.5 A (30 W) | 3.25 A (39 W) | 4 A (48 W) | 5 A (60 W) |
| +5 V | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 1.5 A (7.5 W) |
| +3.3 V | 1 A (5 W) | 1 A (5 W) | 1.5 A (4.95 W) | 1.5 A (4.95 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1 A (5 W) | 1 A (5 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
| Total | 84.4 W | 98.8 W | 134.9 W | 146.0 W |
| % Max Load | 33.8% | 39.5% | 54.0% | 58.4% |
| Room Temp. | 42.2° C | 41.8° C | 41.8° C | 41.9° C |
| PSU Temp. | 41.4° C | 42.9° C | 44.0° C | 45.0° C |
| Voltage Regulation | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass |
| AC Power | 109.7 W | 127.3 W | 172.7 W | 187.5 W |
| Efficiency | 76.9% | 77.6% | 78.1% | 77.9% |
| AC Voltage | 116.9 V | 117.5 V | 116.9 V | 116.9 V |
| Power Factor | 0.630 | 0.634 | 0.640 | 0.642 |
| Final Result | Pass | Pass | Pass | Pass |
| Input | Test 5 | Test 6 | Test 7 | Test 8 |
| +12VA | 6.25 A (75 W) | 7.5 A (90 W) | 8.25 A (99 W) | 9.25 A (111 W) |
| +12VB | 6 A (72 W) | 7 A (84 W) | 8 A (96 W) | 9 A (108 W) |
| +5 V | 2 A (10 W) | 2 A (10 W) | 2.5 A (12.5 W) | 2.5 A (12.5 W) |
| +3.3 V | 2 A (6.6 W) | 2 A (6.6 W) | 2.5 A (8.25 W) | 2.5 A (8.25 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1 A (5 W) | 1 A (5 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
| Total | 169.8 W | 194.1 W | 220.4 W | Fail |
| % Max Load | 67.9% | 77.6% | 88.2% | Fail |
| Room Temp. | 42.1° C | 44.0° C | 44.5° C | Fail |
| PSU Temp. | 45.7° C | 48.5° C | 49.8° C | Fail |
| Voltage Regulation | Pass | Pass | Fail on +12 V | Fail |
| Ripple and Noise | Pass | Fail on +3.3 V | Fail on +3.3 V and +5 V | Fail |
| AC Power | 221.0 W | 259.3 W | 310.7 W | Fail | Efficiency | 76.8% | 74.9% | 70.9% | Fail |
| AC Voltage | 116.5 V | 116.5 V | 115.8 V | Fail |
| Power Factor | 0.644 | 0.649 | 0.652 | Fail |
| Final Result | Pass | Fail | Fail | Fail |
The Logisys PS350MA can’t deliver 350 W or even 250 W. The maximum we could pull from it was 220 W. During our test seven, when we tried to pull around 250 W from it, the power supply exploded after a few seconds. The two switching transistors were the components that fried. To give Logisys the benefit of the doubt, we tested two different samples and got the same exact results.
Figure 14: Bias resistors that burned together with the transistors
Efficiency was always below the 80% mark, varying between 70.9% and 78.1%.
Voltages were inside the proper range except for the +12 V output during test six (220 W), which dropped to +11.34 V. The ATX12V specification says that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.
Noise and ripple levels were high, with the +3.3 V output surpassing the maximum allowed during tests six (56.8 mV) and seven (63.4 mV). During test seven, noise level at the +5 V output was at 51.4 mV, also above the maximum allowed. During the same test, the +12 V output presented a 120 mV noise level, right at the limit. The maximum allowed is 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures.
