Listan, a company based in Glinde near Hamburg, Germany, sells its hardware products for the IT sector under various labels. Among these are power supply units, which, offered under the brand name "Be quiet", have become quite well known. These devices are manufactured in China and Taiwan according to the specifications of the German mother firm. As part of our live stress tests, we tested this top-model among power supply units on the market. This device broke down during 24-hour operation under full load.

After the power supply units from Be Quiet in the 520-watt class broke down during the live stress tests, company representatives paid a visit to the THG laboratory in Munich. In a relaxed atmosphere we talked with Listan's Public Relations officer, Mrs. Renger, and the company's Service Director, Mr. Rex, about important aspects of the manufacture of power supply units and this hard-fought market.

Listan's Public relations officer Dorothee Renger

THG: Are you now able to tell us why the Be quiet! power supply unit failed during the THG live stress test? As a result of these tests you've recalled the Revoltec power supply unit. Why?

Be quiet!: We now know that a slightly loose transistor is connected to the failure of the power supply units during the 24-hour full-load test. The test procedure used by THG subjected the power supply unit to unusual burdens, which in real-life situations - even under high-performance programs - never occur, in our opinion.

We therefore withdrew the Revoltec power supply unit, since when the breakdown occurred we didn't yet know the reasons why the Be quiet! power supply units failed. We preferred to be careful and wanted to first investigate this case ourselves in order to be sure what kind of failure had occurred, and to prevent this in the future.

We therefore thought it was prudent, first of all, to wait for the results of the analysis of the defective model before sending other power supply units to participate in this kind of public performance test. As a result of our discoveries, we will, in the future, install a block for the transistors against vibrations in our power supply units.

We could have provided you with "golden samples" for a new run in the stress test; however these samples would not be the ones used according to the rules we have laid down, which say that we can only send power supply units to performance tests if they are also available to customers in stores. To be more precise: we only release "golden samples" for test phases, when all improvements have been implemented in mass production and are thus available in stores and for retail customers.

THG: Do you carry out your own tests on power supply units? If so, which ones?

Be quiet!: Yes we do. A rough estimate is that there are about 20 to 35 different test procedures which we at Be quiet! conduct before and during the market launch. For example, we carry out continual performance tests, which can be defined as including maximal stress tests of more than two hours. Additionally, we test the efficiency, the stability and tolerances of the individual AC voltage lines, temperatures as well as the AC voltage share of the direct voltage. For the latter, we test to see if the AC voltage share lies within the prescribed maximal values. In addition, we check the active PFC values, and furthermore we cause short circuits ourselves to check the reaction of the power supply units in the framework of the OCP in order to prevent further damage.