Zalman ZM750-HP 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.
First we tested this power supply with five different load patterns, trying to pull around
20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (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. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
+12V1 and +12V2 are the two independent +12V inputs from our load tester and during out tests the +12V1 input was connected to the power supply +12V3 (main motherboard cable and peripheral power connectors) and +12V4 rails (video card auxiliary power connector), while the +12V2 input was connected to the power supply +12V1 rail (EPS12V connector).
By the way, this pattern is similar to the one we used with Corsair TX750W.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 5 A (60 W) | 11 A (132 W) | 17 A (204 W) | 24 A (288 W) | 33 A (396 W) |
| +12V2 | 5 A (60 W) | 10 A (120 W) | 15 A (180 W) | 20 A (240 W) | 22 A (264 W) |
| +5V | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) | 8 A (40 W) |
| +3.3 V | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) | 8 A (26.4 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.8 A (9.6 W) |
| Total | 148.9 W | 297.9 W | 448.1 W | 608.6 W | 740.0 W |
| % Max Load | 19.9% | 39.7% | 59.7% | 81.1% | 98.7% |
| Room Temp. | 47.0° C | 46.9° C | 47.3° C | 48.3° C | 52.1° C |
| PSU Temp. | 48.3° C | 48.9° C | 47.7° C | 50.2° C | 52.8° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 168 W | 332 W | 502 W | 699 W | 873 W |
| Efficiency | 88.6% | 89.7% | 89.3% | 87.1% | 84.8% |
| Final Result | Pass | Pass | Pass | Pass | Pass |
Zalman ZM750-HP proved to be an outstanding product. Efficiency when delivering between 40% and 60% of its labeled power (between 300 W and 450 W) was at 89% and the lowest efficiency we’ve seen was when the unit was delivering 740 W, at practically 85%, which is a number far from low.
Voltage stability was impressive, with all outputs – including -12 V – always within 3% from their nominal values (the maximum allowed is 5%; 10% for -12V).
Noise level was always below the maximum allowed, even though we’d prefer to see lower numbers for the +5 V and +3.3 V outputs. Below you can see noise level when we were pulling 740 W (test number five) from this power supply. Just to remember, the maximum allowed for the +12 V outputs is 120 mV peak-to-peak and the maximum allowed for the +5 V and +3.3 V outputs is 50 mV peak-to-peak.
Figure 15: Noise level at +12V1 input from our load tester with the reviewed unit delivering 740 W (51.4 mV).
Figure 16: Noise level at +12V2 input from our load tester with the reviewed unit delivering 740 W (54.6 mV).
Figure 17: Noise level at +5 V input from our load tester with the reviewed unit delivering 740 W (30.4 mV).
Figure 18: Noise level at +3.3 V input from our load tester with the reviewed unit delivering 740 W (29.6 mV).
Now let’s see if we could pull even more power from ZM750-HP