SMPS Primary Winding Test Result
If you are using Blue Ring Tester to check on the primary winding of switch mode transformer then i would like you to keep in mind that it can’t test switch mode transformer that runs on less than 50vdc. The other day i while i was repairing a small switch mode supply that was using 24 vac as input, i found that the blue ring tester LED will go off if it test on the transformer primary winding. So please do no think that the transformer have problem. It is just that the winding is too less for the result to be shown on the Blue Ring Tester. This type of special small power supply was used in a machinery thus it requires lower ac voltage to run. Consumer electronics SMPS running on either 110 or 220 vac thus the blue ring tester have no problem in checking the power transformer primary winding.