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enter image description here I was using this adapter to power a 12VDC LED strip and felt electric shock from the output wire. When I measured the output with a multimeter, I found both 12VDC and 26VAC on it's output. What could be the cause and can it be fixed? enter image description here

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    \$\begingroup\$ A single picture and no other information isn't the greatest starting point. It would help a lot if you could trace out the schematic. To add it to the question, just edit your question and click the schematic button. \$\endgroup\$ – Dampmaskin Jul 22 '18 at 21:28
  • \$\begingroup\$ If you are using a multimeter (not a scope) and have it set on DCV, and the signal of interest is actually AC voltage, then the reading you are seeing on DMM is not to be trusted. IOW, your mysterious board is outputting AC voltage. \$\endgroup\$ – mike65535 Jul 22 '18 at 21:39
  • \$\begingroup\$ @KingDuken Thank you. I've added a picture of PCB from underneath in the same orientation as the top view picture. \$\endgroup\$ – Jishnu Anilkumar Jul 22 '18 at 21:46
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    \$\begingroup\$ Some inexpensive DVMs mistakenly show a higher voltage reading when set to AC, but actually measuring DC. Try measuring a 9 volt battery with the meter set for AC - the meter will probably show 14 volts or so. \$\endgroup\$ – Peter Bennett Jul 22 '18 at 22:21
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    \$\begingroup\$ felt electric shock ... it is odd that you would feel anything from 12V or even 26V ..... measure the AC voltage between any of the outputs and power line ground .... you may have a leakage \$\endgroup\$ – jsotola Jul 23 '18 at 4:02
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From the photos, this is a very simple inverter power supply. The transformer outputs some 9VAC at a multi-kHz frequency, which is then rectified through the two diodes on the bottom left of the first photo, then filtered through the caps on the bottom.

Because the frequency of the transformer output is in the kHz range, the ripple also is. Your multimeter cannot handle this. The AC reading has no meaning.

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I believe its because there is a class Y capacitor between the input and the output of the transformer, to filter high frequency noise (Example). If you measure with a high Z multimeter, you will measure some amount of mains voltage.

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