I noticed during extra testing of the SX700-LPT SFX-L power supply from SilverStone that I could trigger the Over Temp Protection with a heatgun before the fan kicked on. After asking SilverStone about it, I learned that the fan controller was set to only turn the fan on above 150W load to ensure that the semi-fanless feature really worked. I imagine this was done due to user complaints about the SX600-G and SX500-LG v1.0/v1.1 where the simple thermistor-based controller would cause the fan to turn on even at low loads after the power supply warmed up to operating temperature inside a SFF case.

It turns out though that SilverStone was a bit too aggressive in keeping the fan off and they underestimated the number of people who would buy a 700W power supply for systems that would only draw around 150W for sustained periods (like gaming). So as some of our forum members discovered, with the SX700-LPT in a small case like the SilverStone ML08 and a non-blower video card this could cause the PSU to reach the OTP temperature before the fan had a chance to turn on and cool down the unit.

To address this issue, SilverStone has made a running revision to the SX700-LPT to adjust the point at which the fan kicks on. Here’s the statement I got from Tony Ou, the Marketing Manager at SilverStone:

Hi James, I want to let you know that updated SX700-LPT are now available in the retail channels worldwide (they were actually already available a couple of weeks ago but we wanted to wait until nearly all older stock were sold through before notifying everyone). This was a running change that we implemented while production was still ongoing and we also reworked some of the inventory that was waiting to be shipped out from the factory so there is no version change. To differentiate updated SX700-LPTs, you have to check the serial number. Numbers starting with 1621 or earlier are the original ones while numbers starting with 1624 are the updated units. We underestimated the number of users with mid-range Mini-ITX systems (drawing around 150W on typical load) that would buy our SX700-LPT. Whereas the original cutoff point was 150W as the minimum target for always fan off (due to analog nature of PSU, the trigger point isn’t exact), the updated units will have more relaxed tolerance and will start the fan by around 5% ~ 10% earlier than before (while technically having the same spec. for 150W trigger point). For current owners of SX700-LPT that are experiencing unexpected shut downs, we encourage them to contact the closest SilverStone office for information on how to exchange for an updated PSU. http://www.silverstonetek.com/contactus.php For owners that are not experiencing shut downs, they are still welcomed to exchange for the updated PSU if they wish. However, the updated PSU may start up its fan sooner or more frequently than what they are used to now depending on system and temperature conditions.

The fan turning on just 5-10% earlier may not seem like much so I asked Tony about it and he said with this new revision, in their testing “the SX700-LPT can cope much better in those conditions”.

So there you have it, if you purchased a SX700-LPT right after it was released and the serial number is 1621 or earlier, you can contact SilverStone to arrange a swap with one of the revised units.

Thoughts? Discuss them in the forum here.