The senior model worked with an APC SmartUPS SC 620 at loads up to 350W irrespective of the power source. The junior model worked at 340W and 330W from the mains and battery, respectively. The switching to the batteries was performed without problems.

At a load of 850W the voltage ripple amounted to 21 millivolts on the +5V rail, to 70 millivolts on the +12V rail, and to 43 millivolts on the +3.3. Both high- and low-frequency pulsation can be observed here. The pulsation amplitude was 1-2-millivolt lower with the junior model at a 720W load.

The cross-load diagram looks very good. Both PSUs work without problems through the specified load range.

I have mentioned above that the PSUs came with two fans each, a Delta Electronics EFB0812SHF (a nominal speed of 4700rpm!) and a Sanyo SanAce40 109P0412J3023 (12,500rpm). I only measured the speed of the former fan because the second, 40mm fan proved to be too small for our optical tachometer, let alone being situated deep in the case (I test power supplies with a closed cover to avoid interfering with the thermal conditions of the PSU as well as to protect myself from splinters of transistors in case it fails the test).

The fans proved to be far not the best I had met with. The PSUs both produced a loud high-frequency whistle, much more annoying that the ordinary noise of the PSU fan. This noise is not only audible above the common noise of the system case, but even above the noise of my testbed that is equipped with four powerful fans and has never been intended for quiet operation. I have to admit that the Zeus PSUs are much more pleasing to deal with, even the model with a defective fan. Well, the speed graph that closely approaches the 4500rpm mark speaks for itself.

The efficiency of these PSUs (it coincides up to 1% between the two models) is yet another unpleasant surprise. It barely notched the 80% mark, which is very low for a power supply of that class, wattage and price by today’s standards.

Being comparable to the Silverstone Zeus in price (and being much more expensive than typical 600W power supplies), the PSUs from Zippy are inferior to them in other aspects, mainly in their noise characteristics. Their noise is loud and has an irritating spectrum that lies in the area of high frequencies. To put it simple, these PSUs produce a piercing shrill that is downright unacceptable not only for a home computer, but even for a workstation unless it is a server located in a special room where the noise factor is of the least concern.