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    Need help in reverse engineering this power failure alarm circuit

    Thanks Delta Prime for your response. Sorry for the late reply. Yes, you were right that the working voltage indeed is 5V. However, I can confirm that there are no markings on the electrolytic capacitor, either because it was etched out, or wasn't present in the first place. But the fact that a...
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    Need help in reverse engineering this power failure alarm circuit

    Thanks for your response Martaine. The markings at Q1 and U4 have been etched out as is typical in chinese manufactured circuits. This is why I needed the help primarily. I'm struggling here to figure out this circuit because of that reason. I've used AI to figure out what Q1 and U4 are, but...
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    Need help in reverse engineering this power failure alarm circuit

    Namaste, I need help to reverse engineer and get the schematic diagram and the BOM of a power failure alarm which has the attached circuit board. It runs on a 9V battery during power failure, and provides a 120db alarm aound output. Can anyone please provide any help.
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