UL Numbers From Underwriters Laboratories
"Underwriters Laboratories, an independent firm working with product safety certification, has been active in the field of product testing and preparation of safety standards for more than a century. UL evaluates more than 19 000 types of products, components, materials and systems annually. Every year more than 20 billion UL marks are placed on products from 66 000 different manufacturers. The UL Group and its network of service providers include 68 testing and certification labs worldwide, serving customers in 102 countries."--From the About UL page at ul.com
Essentially, this means that all PSUs sold on the North American market must be marked with a UL number. This number should identify the actual manufacturer of a product. However, not every PSU has such a number. UL number omission on a North American product might indicate poor quality.
Step 1: Reading the UL Number
To find the UL number, there's no need to open your PSU or de-solder anything. Simply open your PC and look at the power supply's label. The UL number usually begins with an "E" followed by a string of numbers. See the three examples below.

If your PSU has such a number, you can move onto the next step, finding out what it means.
Online UL Number Query

Now let's find out more about your PSU. Go to the UL Online Certifications Directory and enter the UL number in the UL File Number field. If the number exists in the database, you should immediately see the result. If not, the number is invalid, fake, or the manufacturer no longer exists.


Huh? Since when Seasonic is not the maker of their products?
Nice article and much needed. Thanks
The ones in question were probably older ones with cheap caps that failed. And probably made by one of the lesser companies there too.
I am not sure that Channel Well is that great. I had Antec Smartpower 2.0 die on me. Currently I own EarthWatts 500D from delta. Read that this is a decent unit.
That can happen and I'm sorry for you.But the fact is that there are quite a few PSUs form them for Antec and Corsair that have received great reviews form sites like jonnyguru.
http://www.hardwaresecrets.com/article/How-to-Discover-Your-Power-Supplys-Real-Manufacturer/370
When i want the best power supply for any system i'm building my first choice is Seasonic.
Perhaps you are right. It have been years ago when it died. I even used Thermaltake Purepower for a few years after that before I purchased EarthWatts. Thermaltake still kicking but I decided that it was time to change. Anyway, things change and I decided to give Antec a second shot. I would say, the best advice would be to read reviews and not just any reviews where they just use PSUs in a system, but reviews where they measure voltage regulation, DC quality, ripple, etc. and open units to see if there is turd inside, or something worthy.