The network router in the basement was not working and I found its wall wart was hotter than it should be. When you work with electronics you get a feeling for if something something is getting too hot, even when it is encapsulated in a plastic case.
As expected there was no power at the output (it is rated 24 V DC / 1.2 A). After opening the device forcefully, I found the schottky diode on the secondary side shorted. Everything else seems okay. So I wanted to know what was heating up.
With primary power applied, the SMPS runs in intermittent mode as it should be due to the shorted secondary side. But the MOSFET on the heatsink gets very hot. I measured over 100°C after a few minutes. Probably not the best design I guess.
I already replaced the wall wart by something I had floating around, so this is not a repair issue. More kind of a informational post-mortem analysis.
And... maybe someone has a clue about
chip identification: I was curious about the 6-pin control IC labeled
DP81 OH18.
It's a TSOP6 package with GND on pin 1, feedback on pin 2, output on pin 4 and Vcc on pin 5.
I guess it is a clone of
NCP1250 by ON Semi but is there no kind of search engine for those SMD chip markings? Octopart and Duckduckgo had no clue. Google finally pointed into the right direction...
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