Articles: Cases/PSU

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The A-55GA is cooled with an MGT12012HB-025 fan from Protechnic Electric and equipped with the following cables and connectors:

  • Mainboard cable with a 24-pin connector (54cm long)
  • CPU cable with a 4-pin connector (55cm)
  • CPU cable with an 8-pin connector (55cm)
  • Two graphics card cables with one 6-pin connector on each (55cm)
  • One cable with a Molex and a floppy-drive plug (55+15cm)
  • One cable with three Molex and one floppy-drive plug (54+15+15+15cm)
  • One cable with four Molex connectors (53+15+15+15cm)
  • One cable with four SATA power connectors (54+15+15+15cm)
  • Cable of the fan’s tachometer (31cm)

The selection of connectors is good except that the SATA cable is only one. In many system cases it is going to be impossible to connect both a hard drive and a DVD drive without adapters. The abundance of Molex connectors is going to be uncalled for, however. I guess the manufacturer should have replaced one of the PATA power cables with a SATA one.

The PSU has a high load capacity of the +5V and +3.3V rails but the +12V power rail, the most demanded one in a modern computer, has a maximum current of 30A only. It means that the maximum effective output power of this PSU, i.e. the power it can yield considering the typical distribution of load among the different power rails, is about 400 watts.

The PSU worked without problems at a load of 515W in my tests.

When working with an APC SmartUPS SC 620, the PSU was rather unstable: the UPS switched to the batteries normally at a load of 350W but then produced a gurgling sound, reported overload and shut down. It was only at a load of 300W and lower that the pair could work normally on the batteries. In this case, when the switching to the batteries is performed well but the operation is unstable, you can solve the problem by using a more expensive UPS with a sinusoidal output voltage.

The output voltage ripple is within the allowable limits, but there are also high occasional spikes in the oscillogram.

The output voltages are not very stable. The voltages on the +12V and +5V rails sag under load. And if the sagging +5V voltage is not a problem for a modern PC, the reduction of the +12V voltage by over 3% below the nominal value may make some graphics cards unstable. Thus, the maximum reasonable load on this PSU’s +12V rail is 250-300 watts. This is more than enough for a configuration with a fast CPU and one mainstream graphics card, though.

The PSU is about 80% efficient. It even hits 82% at one point of the graph but then its efficiency droops again as the load grows up. That’s an acceptable result, but you can see PSUs with an efficiency of 85-87% today.

The PSU is very quiet under low loads but the fan starts to accelerate linearly at loads above 150W, reaching 1700rpm at 300W. As a result, the A-55GA is just average in terms of noisiness.

Summing it up, the A-55GA is a typical midrange power supply suitable for configurations with one mainstream graphics card. The effective output power of this PSU is about 400W or even less considering the instability of the output voltages. It is not quiet and there is nothing exceptional in its other characteristics. And it has got a lot of cheaper competitors in its product class.

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