I recently came about one such transformer while fixing a boiler PCB and I suspect it's damaged. How do I test it?
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\$\begingroup\$ Welcome to EE.SE. In contrast to purely magnetic transformer a SMPS is a very complex circuit. It can be built in very different ways, so that no simple answer can be given. When you ask: "There's no water coming from my garden hose", we could at least say: "check the valve". But when you say, "the plates keep coming dirty out of the dishwasher", there's no way to analyse it without further information. Same for the SMPS. \$\endgroup\$– AriserCommented Feb 14, 2020 at 15:26
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2 Answers
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Checking SMPS transformers is always a bit hard:
You probably have no information to information that would tell you what the intended winding ratios are; and without, shorts between traces on either side are hard to detect.
Even worse, if it's e.g. a flyback configuration, it'd be non-trivial to reliably test isolation non-destructively, since these things tend to fail "OK-ish", until environmental parameters (e.g. humidity) change.
Also, since they are typically relatively custom components, it's usually questionable whether diagnosing the transformer is helpful: If that's broken, you'll have a hard time to find replacement, since you don't know the original specs. It's one of the things that typically lead to "oh, the supply is broken, replace it as whole". Also, in most SMPS, it's far more likely that semiconductor parts failed than the magnetics, so you're probably barking up the wrong tree.
answered Feb 13, 2020 at 19:14
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About the best you can do is to ohm out the windings for continuity, or maybe check for a short between a winding and the core, for instance. Otherwise, as Marcus said, you're basicaally out of luck.
