On 08/19/2017 03:17 AM, Dominique Carlier via cctalk wrote: > Hello Marc, > > In fact no, i am not really sure, I checked twice all the > big filtering caps but as you with a low voltage tester. > These caps comes apparently from a new old stock and some > doubts persists now. > I admit, I don't know how to test these caps at rated > voltage with my tools or in situ with the caps inside the > working (and thus closed/packed/connected) PSUs > It could also be an open rectifier diode. The caps might store enough charge to keep the regulator from dropping out at light load, but the DC input sags under more load. You could check for AC on the DC output when it starts to fail. It could also be a fuse socket that has developed some resistance, although when that gets bad, the heat causes the fuse to fail. We had a Versatec printer that this would happen to every 5 years or so. The fix was to clean the fuse clip with the finest sandpaper available and put in a new fuse (even if you caught it before the fuse blew.)
Jon