Zalman ZM750-EBT PSU Review

Reviews
By Aris Mpitziopoulos
published

Zalman's new EBT line consists of four PSUs ranging from 650W to 1kW capacity. Today, we're testing the ZM750-EBT, which, thanks to a low price, achieves a good value score. But how does it fare in terms of absolute performance?

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Ripple Measurements

To learn how we measure ripple, please click here.

The following table includes the ripple levels we measured on the rails of the Zalman ZM750-EBT unit. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V and 5VSB).

Swipe to scroll horizontally
Test12V5V3.3V5VSBPass/Fail
10% Load16.4mV12.5mV11.8mV14.7mVPass
20% Load20.6mV17.8mV16.2mV18.3mVPass
30% Load23.2mV22.7mV17.7mV24.2mVPass
40% Load27.7mV30.1mV22.0mV27.2mVPass
50% Load30.5mV37.9mV23.2mV31.6mVPass
60% Load35.1mV45.2mV26.7mV37.4mVPass
70% Load40.0mV38.3mV29.3mV44.1mVPass
80% Load45.4mV42.7mV32.0mV50.7mVFail
90% Load52.1mV46.9mV35.5mV56.6mVFail
100% Load69.2mV58.4mV43.5mV68.8mVFail
110% Load91.3mV63.1mV48.6mV82.7mVFail
Cross-Load 124.8mV22.5mV19.1mV34.3mVPass
Cross-Load 270.4mV48.7mV43.1mV59.5mVFail
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Ripple suppression clearly isn't among this PSU's strengths. The 5VSB rail failed not once or twice, but five times in keeping its ripple within limits. And the 5V rail went over 50mV in our full load and overload tests. We also measured close to 70mV at +12V under full load. That's a high reading, given that we don't want to see anything above 50mV, especially from PSU that utilizes a modern platform. Finally, the 3.3V rail performed significantly better, though it also has a problem with ripple control and isn't able to match the competition. Sirfa should revise this platform and fix its ripple performance.

Ripple Oscilloscope Screenshots

The following oscilloscope screenshots illustrate the AC ripple and noise registered on the main rails (+12V, 5V, 3.3V and 5VSB). The bigger the fluctuations on the screen, the bigger the ripple/noise. We set 0.01V/Div (each vertical division/box equals 0.01V) as the standard for all measurements.

Ripple At Full Load

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Ripple At 110-Percent Load

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Ripple At Cross-Load 1

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Ripple At Cross-Load 2

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Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.

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13 Comments Comment from the forums
  • Onus
    Although the article does mention safety, a very valid point, it still managed to imply that a single-rail PSU was "better" due to the complexity of managing rail assignments so as to not trip OCP protections. I've have not seen a multi-rail PSU actually get dinged for this in a review for maybe 8-10 years; it seems that everyone does OCP "right," so this is no longer an issue, ever. That being the case, the greater safety of a multi-rail design is superior.
    I'll need to make at least another pass through this article, but failing on +5V ripple under heavy load probably makes this a solid tier-3 unit; I'm not going to run screaming if I see one, but I wouldn't buy it either.
    Reply
  • JQB45
    Tier-3 might be generous. There were a lot of cons. What good is a 7 year warranty if the PSU takes something else out in addition to the PSU.

    CONS: Ripple • Noisy under stress • Hold-up time • Inrush current • Sleeve-bearing fan • Single EPS connector • Inaccurate PWR_OK signal

    Also it must also be strongly pointed out that this unit does not meet ATX specifications.
    Reply
  • Onus
    True, but the tier-3 units are the ones considered solid for lighter loads. Those cons are why I certainly would not buy one for a gaming or rendering rig, but for the typical PC that may not need even half this power, I wouldn't worry about it.
    Reply
  • Sakkura
    The fact that it's not just barely breaking the ATX spec at 100% load, but already starts to go out of spec at 80% and then has two rails well out of spec at 100%, is what makes this a tier 4 unit, and a clear "do not buy" regardless of price.
    Reply
  • yyk71200
    One would expect that a gold rated powersupply would be at least a solid unit and a safe buy. Guess not. Shouldn't buy one simply based on advertised efficiency rating.
    Reply
  • Onus
    That's definitely true. Coolermaster taught that lesson quite well.
    Hmmm, this one does seem a little worse than I thought at first. Any chance this particular unit had a problem? I'd think ripple could be fixed with a minor capacitor improvement, without adding too much to the price. Hopefully Zalman is paying attention.
    Reply
  • JQB45
    17328110 said:
    That's definitely true. Coolermaster taught that lesson quite well.
    Hmmm, this one does seem a little worse than I thought at first. Any chance this particular unit had a problem? I'd think ripple could be fixed with a minor capacitor improvement, without adding too much to the price. Hopefully Zalman is paying attention.

    agreed
    Reply
  • COLGeek
    It is interesting to see Zalman developing this line of PSUs. Hopefully, they will be better than previous generations. Had a couple Zalman PSUs a few years ago, when I used to use Zalman heatsinks.

    One died days after the warranty expired and the other about a month after. I'll give Zalman credit, they made right by me by exchanging both, but it was a painful process.

    While I would not recommend these current products, I can at least "tolerate" them in budget builds.
    Reply
  • turkey3_scratch
    I would think anything out of spec should be Tier 4. Ripple is trash. 3.3V rail was on the brink of being out of spec. 12V was also quite terrible at 90mv.

    Anyway, I like your power supply reviews, Toms. You go more in-depth than any review site for power supplies (Hardwaresecrets, Johnnyguru).
    Reply
  • Sakkura
    17328110 said:
    That's definitely true. Coolermaster taught that lesson quite well.
    Hmmm, this one does seem a little worse than I thought at first. Any chance this particular unit had a problem? I'd think ripple could be fixed with a minor capacitor improvement, without adding too much to the price. Hopefully Zalman is paying attention.

    Considering the same platform performs decently in the Silverstone unit, there's at least some hope that Zalman can go back, adjust a few things, and get a decent budget unit out of this.

    Edit: I went back and looked at the Silverstone review. Ripple suppression was really good up to 90% load, then the 5V and 3.3V rails jumped hugely, especially the 3.3V. They did stay within ATX spec, but just barely. The 5V ripple went from 13.1mV at 90% to 40.5mV at 100%, 3.3V ripple went from 14.1mV at 90% to 49.9mV at 100%. Obviously the 3.3V ripple went out of spec at 110% load, as well as one of the crossloads, but that's a lesser sin.
    Reply