A Detailed Look
One of the first things you will notice when unboxing the SX500-LG power supply is the bright yellow label wrapped around the PSU. This is to let users know this power supply features a semi-fanless operating mode. The cooling fan doesn’t start spinning when the PSU is first turned on; it only spins up after the load and internal temperature reach ~41°C.
The SilverStone SX500-LG power supply enclosure features a scratch resistant, lead free black matte finish and measures 130mm (5.3”) deep. The back panel includes a power receptacle and master On-Off switch.
The power supply uses a 120mm cooling fan made by Globe Fan (S1201512MW), which is rated for 0.35A at 12 VDC. The fan uses sleeve bearings for quiet operation but potentially sacrifices the longer-life offered by a high-quality ball bearing fan.
The SX500-LG incorporates an “intelligent semi-fanless” fan speed controller, which allows the fan to turn off for silent operation at low loads.
The power supply includes five nicely labeled sockets on the front panel for connecting the modular cables.
The PSU comes with a basic assortment of all modular flat, ribbon-style cables. As we mentioned before, if you find one or more cables are too short for your particular build (especially if you are installing the SX600-G in a larger ATX enclosure) SilverStone offers a complete line of full-size modular cables that can be purchased separately. All of the sleeved cables in the PP06 and PP07 Series will work with the SX600-G SFX power supply.
(Courtesy of SilverStone)
For this particular power supply, SilverStone is using High Power as the OEM for the SX500-LG power supply. A modern design is used to obtain relatively high efficiency (80 Plus Gold) and the secondary features dual DC-to-DC converters to produce the 3.3V and 5V minor rails (on the left side in the photo below).
With the cover/fan assembly removed, you can see the internal layout of the SX500-LG power supply. The main filter capacitor on the primary side is a Rubycon unit rated for 390uF, 420V, and 85°C. All of the capacitors used in the SX500-LG V1.1 are high quality Japanese made units. The original SX500-LG V1.0 used Japanese made capacitors on the primary but mostly Taiwanese capacitors on the secondary.
The extra 30mm of chassis depth provides room for good spacing and airflow from the larger 120mm cooling fan. The overall build quality appears good and the soldering on the PCBs is also very good.
An important thing to note
An important thing to note about the ‘fanless’ mode: The entirety of the fan control system is composed of a thermistor attached to the internal heatsink that controls fan voltage, and Silverstone using a fan which happened to have a startup voltage that worked well with the voltage produced by the thermistor and desired startup temperature. The problem being that it is an entirely dumb control system, with only the thermal load of the heatsink (or rather, the thermistor strapped to the heatsing with a short length of heat-shrink tubing) providing any hysterisis.
The upshot being that under idle/low-load conditions, the fan will tend to hover just at the startup voltage. Unfortunately, the fan will also make a lot of noise in this regime, with clicks coming from startup/shutdown and buzzing just below startup as energy is dissipated into the rotor sufficiently to produce audible vibration but insufficient to overcome static friction and start the rotor moving.
Sadly, this makes the PSU in practice a lot noisier than it should be. Infuriatingly, without the ‘fanless mode’ the PSU would be really quite silent. Silverstone (via Tony Ou on the HardOCP forums) even tried their own slim 120mm fan, [url=http://hardforum.com/showpost.php?p=1041479391&postcount=596]and rejected it doe to not spinning down[/url], meaning the PSU is semi-fanless at the expense of actual low-noise operation!
There are quite a few other PSU sellers using the same Sirfa platform that Silverstone are using here, and with different fans, so if they avoid the ‘semi-fanless’ mode those should in practice be quieter. Or the SX500-LG could be modified with Silverstone’s own fan if you’re willing to void the warranty (the fan is soldered to the PSU PCB). Option 3 would be to strap a thick 120mm fan to the outside to keep the PSU cool enough that the thermistor never gets hot enough for the fan to approach the startup voltage in the first place.
I’ve replaced the stock fan
I’ve replaced the stock fan in my SX500LG with the Silverstone FW121 that Tony Ou used. It’s not perfect as the fan still has a quiet buzzing/chatter while spinning, but it’s a good improvement over stock.
Also the stock Globefan was not soldered down. It used a 2 pin fan plug+socket, with some sort of glue on top (not engulfing) to secure it.
My next plan is to swap the FW121 for a Scythe Slip Stream SY1225SL12M as it has a very low starting voltage, although this is a full thickness fan that will need to be mounted to the outside.
I recently purchased this
I recently purchased this power supply and it’s installed in my Xigmatek Nebula ITX case with Z97 mobo, 4690k, GTX970 ITX and even while gaming (Shadow of Mordor – high/ultra settings for example) the fan on the psu still doesn’t spin up. I figured out that because my case has negative air pressure, air is being drawn in from the rear of the power supply keeping it cool enough so it never gets to the target temperature for the fan to kick in – making it passively cooled. Fantastic power supply – I’d just rather it didn’t use semi fanless mode as the Nebula case is designed so that the psu aides the removal of warm air. My case, GPS and cpu temps are all fine, I just think they’d be a little lower with the extra exhaust provided by a spinning psu fan.