short answer: If uncertain, replace it. Longer answer: there will be people who say to apply a multimeter or voltmeter to envision the DC outputs to be certain in the event that they're in spec. the issue with this attitude is two-fold: a million) ninety% or greater powerful of undesirable/defective potential substances will attempt wonderful once you examine the DC outputs with a multimeter. a potential grant is an lively ingredient...it does not basically convert AC to DC. Plus, making use of a multimeter does not effectively attempt a potential grant unit *over the years*. (a short-term examining of +12.04V, as an occasion...says no longer something in any respect smart) 2) For the few (share smart) potential substances that are so some distance out of spec that they are going to attempt undesirable on a multimeter... there is going to be little question that the potential grant is undesirable earlier you examine it with the multimeter. So at proper, attempting out the DC outputs might permit you recognize WHAT you will desire to ALREADY recognize. (that is redundant) possibly ninety 5% of the time that a potential grant is *suspected* of being undesirable, it is unquestionably undesirable. potential substances fail with alarming frequency. it is likewise considerable to observe that infrequently does a potential grant fail in a manner that it will no longer do something. generic failure mode is, gadget will activate, followers will spin, LED lights will get rid of darkness from, annoying drives will spin up...yet you get no BIOS beeps and no video. that could be a typical failure mode for a potential grant. the proper attitude to "attempting out" a suspect potential grant is to purchase a stable call variety, NEW potential grant and installation that.