The division of the +12V power rail into four channels is traditionally virtual, i.e. there is actually one high-power 12V rail inside the PSU which is split in four by means of four shunts and an over-current protection circuit.
The cross-load diagram looks well. The only thing I can cavil at is the +5V voltage which goes down considerably at high loads. This is not going to be a big problem for a modern computer system where the consumption from the +5V and +3.3V rails is never higher than a few dozen of watts. Otherwise the cross-load diagram proves that the power supply can really yield its full power along one 12V channel only.
The PSU proved to work normally under a sustained load of 680W and the temperature of the heatsink with the diode packs, which is the hottest one, was not higher than 70°C at that.
The voltage ripple on the +5V, +12V and +3.3V rails was 42, 78 and 43 millivolts, the allowable maximums being 50, 120 and 50 millivolts, respectively. Most of this ripple is caused by short-term spikes at the moments the inverter’s transistors are switched over. Low-frequency pulsations (at the double mains frequency, which is 100Hz in our case) are missing altogether.
The Epsilon is cooled with a Protechnic Electric MGA12012HB-O25 fan whose speed control circuit is located on the main PCB (in previous PSU models from FSP it used to be placed on a separate small card fastened to a heatsink).
The fan speed depends linearly on the PSU load (on its temperature, to be exact) across all the measurement range. This PSU is among the quietest ones ever tested in our labs at loads lower than 300-400W and is definitely quieter than any earlier produced power supply from FSP, except for fan-less ones, of course. THN series PSUs with 120mm fans brought FSP the reputation of a manufacturer of quiet, but not exactly silent, PSUs. The GLN series is now among the best as concerns its noise characteristics.
When you turn the power supply on, the fan may be altogether idle for the first 2-3 minutes, but as the PSU gets hotter and the voltage on the fan rises, the blades begin to twitch a little (the fan’s electronics are trying to spin up the fan with such jerks) and then get to rotate constantly.
The manufacturer declares an efficiency of 85% and is honest about that, as you can see. The power factor is not so good, but the difference between the Epsilon’s 0.97-0.98 and many other PSUs’ 0.99 is really negligible.
So, the FSP Epsilon FX700-GLN power supply is a very well-made model and is a worthy replacement for the previous THN series. It is a very quiet and high-wattage unit that yields stable voltages and is well equipped with various connectors. It is also not very expensive at $180 which is not too much for a PSU with characteristics like these. The Epsilon series comprises only two models, FX600-GLN and FX700-GLN, but the GLN series of OEM power supplies includes a number of models from 250W and higher, so it is quite possible that more models, also in the entry-level sector, will be available to users in retail shops.