X-bit labs

In Win Power Supply Units Roundup (page 2)

Category: Other

by Oleg Artamonov

[ 07/13/2005 | 10:51 AM ]

The PSUs have a typical (for their class) selection of connectors:

• A 20-pin ATX connector on a 41cm cable
• A 4-pin ATX12V connector on a 43cm cable
• A cable with two Molex connectors for disk drives (24cm from the PSU to the first connector and 15cm more to the second one)
• A cable with two Molex connectors for disk drives and with one floppy mini-plug (24cm to the first connector and 15cm more to each next connector)
• A cable with one Molex connector and one mini-plug (24cm+15cm)

There are no power connectors for SATA drives, but it is normal for an inexpensive ATX12V 1.2 product. A more serious drawback is that the 24-cm-long disk drive cables may be too short in large system cases.

The cross-load characteristics of the power supplies aren’t ideal, but good. These PSUs will handle a midrange computer quite confidently. The only surprising thing is the low stability of the +3.3V voltage. It usually deviates by no more than 2-3% from the norm, but here it reached 5%. Still, this shouldn’t be a problem anyway.

There’s distinct voltage ripple at full load (250W) but it never goes outside the prescribed limits: 30 millivolts on the +5V rail and 80 millivolts on the +12V rail, the allowable maximums being 50 and 120 millivolts, respectively. There is no low-frequency ripple here (at the double frequency of the power grid, i.e. at 100Hz).

The PSU is equipped with one 80mm Top Motor DF1208SH fan. The speed of this fan is controlled rather ineffectively: the speed changes with a jump as the load gets over 150W. So, the power supply is going to be very quiet at small loads (less than 150 watts), but at high loads the noise will grow up noticeably – the fan rotates at almost 3000rpm at its full speed.

The efficiency of the two units is average, about 75%, while the power factor differs, of course. It is almost 0.8 with the unit that is equipped with a passive PFC device.

So, these two power supplies left me perplexed. They are neatly assembled and have good parameters, but the short length of the cables and the manufacturer’s intention to overstate the allowable wattage of the units are disturbing. Yet anyway, they will both suit nicely for low-end and midrange computer configurations.