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Rosewill Photon-1200 PSU Review

Today, we evaluate Rosewill's Photon-1200, manufactured by Sirfa, featuring fully modular cabling, Gold-rated efficiency and a high watt-per-dollar ratio.

Ripple Measurements

To learn how we measure ripple, please click here.

The following table includes the ripple levels we measured on the Photon-1200's rails. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V and 5VSB).

Test12V5V3.3V5VSBPass/Fail
10% Load29.2mV10.2mV24.0mV9.0mVPass
20% Load38.2mV10.1mV25.2mV9.0mVPass
30% Load46.1mV11.2mV26.7mV9.8mVPass
40% Load58.2mV13.4mV28.4mV11.6mVPass
50% Load69.6mV15.2mV29.3mV12.5mVPass
60% Load77.5mV14.1mV31.2mV13.8mVPass
70% Load86.2mV16.2mV36.4mV15.3mVPass
80% Load94.7mV18.9mV39.5mV17.0mVPass
90% Load105.0mV31.0mV45.1mV18.3mVPass
100% Load115.9mV41.2mV48.6mV24.5mVPass
110% Load126.7mV56.0mV63.2mV32.4mVFail
Cross-Load 146.2mV15.2mV23.0mV9.5mVPass
Cross-Load 2113.3mV55.8mV61.0mV29.8mVFail
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Ripple suppression isn't good, especially at operating temperatures that exceed 44 degrees C. On the +12V rail, we don't want to see results above 50mV. Clearly, this platform lets us down with ripple measurements close to 120mV. The Photon-1200 cannot operate properly at high ambient temperatures and this is why it didn't manage to keep ripple suppression under control, failing in the 110 percent and Cross-Load 2 tests. Keep this thing's operating temperature below 40 °C, just as Rosewill recommends.

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 usually set 0.01V/Div (each vertical division/box equals 0.01V) as the standard for all measurements; however, in this case we had to increase to 0.02V/Div for the +12V rail.

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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  • MasterMace
    Sirfa has produced too many poor units in the past to get any leeway or benefit of the doubt. It failed 80 Plus Gold in the hotbox at 100% load.
    Reply
  • boller
    I have a good perspective on that ripple thing: just finished repairs of a PC power supply and when I was measuring ripple I found it was out of whack (300 mV pp). After some investigation I found out that measuring ripple is a tricky thing. Tom's description on how they do it is very incomplete. Eevblog guy spent an entire episode on ripple. In my case I had to do this: limit oscilloscope bandwidth 20 MHz, instead of the grounding clip use that spring attachment and measure loaded PSU at the last cap before leads. Ripple went down from 300 to 48 mV pp.
    Reply
  • Aris_Mp
    First of all you don't just hook a scope on a PSU's output and measure ripple else you will catch huge spikes, like in your case, which will totally alter the measured result.

    Secondly most users aren't interested on how I do things (and even if I elaborated on all the procedures I follow only a fraction of them would understand them) but about the final result. For me the most important is to explain what ripple is and how it can affect the components of a system.

    Thirdly. You don't have to watch Dave to see how ripple is measured properly. You can check on the ATX spec which includes the ripple measurement procedure. I follow all guidelines of the ATX spec so if you need to see how I measure ripple or load regulation just take a look at them. In any case the following scheme will show you how to measure ripple on a PSU.

    Reply
  • boller
    No need to be defensive, I was just pointing out that your _description_ is incomplete, not that you do it wrong. Although it would be nice for you to place a note over there saying that actual procedure involves some additional caps and an honest to god differential probe (!)
    Reply
  • Aris_Mp
    I just replied to your concerns. No need to think that I am defensive because clearly this is not the case with me.

    I already stated that I don't mention how I measure ripple since among others all of us reviewers have to follow the ATX spec procedure. There is no point in repeating the whole ATX spec from the moment that anyone can download and read this spec with a simple google search.

    Besides these two caps (which are already pre-installed on the fixtures that most of us reviewers have. There also present on loaders like the Sunmoon ones) and the good quality probes you also need to isolate all external noise that can pass from the PSU's EMI filter. In other words you need to provide "clean" power to the PSU. Personally I do this with a Chroma AC source and in the near future I plan to get a online UPS with some extra circuits for EMI/noise protection which will feed the AC source (so I will have two layers of protection). In order to check if your line is clean firstly take some readings on the major rails (+12V, 5V and 3.3V) with the PSU in standby. If you see increased ripple (normally it should be close to zero mV) then your scope picks up noise or the PSU isn't properly isolated from the rest devices on your home/lab.
    Reply
  • CTurbo
    It's not a bad unit, but it's not competitive at all. It's more expensive than an EVGA G2 1300w Gold and and Rosewill Capstone 1200w Gold, and almost as much as an EVGA P2 1200w. Yikes!
    Reply
  • Mac266
    Shame it performed badly, a cheap high rated supply could stir the market up nicely!

    It's not a bad unit, but it's not competitive at all. It's more expensive than an EVGA G2 1300w Gold and and Rosewill Capstone 1200w Gold, and almost as much as an EVGA P2 1200w. Yikes!

    CTurbo! How ya been mate?
    Reply