Articles: Cases/PSU

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The PSU features independent voltage regulation (the three choke coils in the left of the snapshot) and active PFC (the separate card with a heatsink in the right of the snapshot).

The PSU complies with the ATX12V 2.0 standard, but the allowable load on the +12V rail is but slightly above the requirements to 400W models (29A as opposed to the ACR-PS2100’s 30A). On the other hand, the Ryanpower2 has a good load capacity of the +5V and +3.3V rails, but the question is if you really need it in practice? It may come in handy in old computers, but such systems can hardly need a 500W PSU.

The following cables are supplied with this power supply:

  • Mainboard cable with two connectors: a 24-pin on the PSU end and a 20-pin on the mainboard end; it is 47cm long
  • CPU cable with 4-pin ATX12V connectors on both ends; 48cm
  • One cable with three Molex connectors and one floppy drive connector; 28cm to the first plug and then 9cm more to each next plug
  • Two cables with three Molex connectors on each; 28cm+13cm+13cm
  • One cable with three SATA power connectors on each; 28cm+10cm+10cm
  • One cable for powering external fans with four connectors; 28cm to the first plug and 13cm more to each next plug
  • An adapter from two Molex connectors to one 6-pin graphics card connector

As I mentioned above, it’s impossible to connect normal SATA connectors with 3-volt power (the enclosed connectors just lack this wire) or a separate graphics card cable to this power supply. You will also have to purchase another mainboard cable if your mainboard has a 24-pin power connector; the enclosed cable has a 20-pin connector only. To be exact, the cable has a 20-pin plug on one end and a 24-pin plug on the other, but if you attach the latter to your mainboard, you’ll have to use the 20-pin plug for the power supply, transferring the problem of connector overload under high currents from the mainboard to the PSU (and this is the very problem the new 24-pin connector has been introduced to solve). The 24-pin connector is necessary: many manufacturers of mainstream PCI Express graphics cards with a peak consumption of 50-60W do not install additional power connectors on their devices, so the mainboard’s power connector has to bear the whole load.

The power cables for hard and optical drives are rather short and may give some trouble to owners of big system cases.

The cross-load characteristic of this power supply looks as superb as can be expected from a model with independent voltage regulation. On the other hand, the unit only reaches its maximum output power when the +5V and +12V rails are both under max load which is a virtually impossible situation in real life. In other words, if this PSU proves insufficient for a modern computer, it will be due to an insufficient load capacity of its +12V rail rather than due to its low overall wattage.

Well, I never happened to get the full declared output power from this power supply. In order to measure the speed of the fans and to check the PSU’s operability under full load, I was steadily increasing the load from 50W to the allowable maximum, stepping 50-100W. The PSU has to work for 30-40 minutes at each step. The ACR-PS2100 passed the step of 450W successfully, but then burned down at a load of about 510W. It put on an impressive show at that, with a series of plopping sounds and sparkles flying out of the fan grids… The subsequent autopsy revealed that the high-voltage section was all burned out (not the active PFC, but the PWM controller itself, farther along the circuit); the heatsink and surviving components were all sooty.

This is why I couldn’t measure the voltage ripple on the PSU’s output.

The power supply has two fans, an 80mm fan from an unidentified manufacturer and a 92mm JDDA SDF9225S. Its speeds are varied depending on the temperature in a linear-like manner. The PSU is quiet at low loads, but at high loads the fans become audible, even though not actually loud.

The efficiency of this power supply is rather low as today’s PSUs go – a mere 74% at the maximum. Of course, this meets the requirements of the standard, but you should be aware that many other PSUs are 80% and more efficient.

Thus, the Ryanpower2 ACR-PS2100 hasn’t any big advantages over its predecessor, the ACR-PS2094 model. The unit couldn’t work under the maximum specified load and it is also not free from the drawbacks of the junior model like too few cables or a paltry selection of connectors (you can’t attach a graphics card power cable; there are no connectors for SATA drives with +3.3V power). Contrary to the boastful epithets in the manual and on the box, this power supply is not better, but inferior to many competing products. The only definite plus of this PSU is the excellent stability of its output voltages.

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