I was playing around with a 16V output AC adaptor and I unfortunately shorted the output VCC and GND by mistake. A spark occured at the end of the wires. Since then, the output voltage is around 0.3 V. I was wondering if there is a common component failure that would explain this regulator failure (which part of a regulator is most likely to fail when the outputs are shorted?). I opened up the device, but there are no signs of component damage anywhere.

Thank you!

Edit: I should have mentioned it is a wall AC-DC adapter and regulator (for a camera I believe, looks like any laptop regulator though) so inputs 120V AC and outputs 16V DC

Hopefully photos can help determine the functionality of the circuit. I really haven't a lot of experience with AC PSUs yet... Hopefully I can learn a bit from this.

So the spark was seen at the end of the wire, but it seems it as destroyed an onboard component... I find this strange.

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  • 1
    \$\begingroup\$ Hmm... without seeing the device and a schematic, how is anyone else supposed to understand your device? This is impossible without lots more information. Click the edit button under your question and tell us lots more about this device, pictures would help. \$\endgroup\$
    – rdtsc
    Dec 19, 2020 at 21:42
  • \$\begingroup\$ If it's unregulated. check the bridge rectifier. \$\endgroup\$
    – user16324
    Dec 19, 2020 at 21:56
  • \$\begingroup\$ some of these devices quit until you turn the power off if they get shorted, if you've already tried that it's busted, you'll have to find the bad part and replace it. \$\endgroup\$ Dec 19, 2020 at 22:52
  • \$\begingroup\$ please post a picture of the inside of the adapter \$\endgroup\$
    – jsotola
    Dec 19, 2020 at 23:40
  • 1
    \$\begingroup\$ Check the mains fuse for continuity. That's the black cylindrical object behind the connector. The power supply is poorly designed if it cannot withstand a short on the output. \$\endgroup\$ Dec 20, 2020 at 1:15

1 Answer 1


You said:

I really haven't a lot of experience with AC PSUs yet...

Beware! PSUs can cause fire, explosion, property damage and personal injury etc. (not just from electrocution, but indirectly too e.g. a loud "bang" can cause a person to quickly move their hand away and then impact their hand against other objects, causing injury). I recommend you research about relevant safety precautions for working on such PSUs - that is a whole topic on its own. Using any information I have given is completely at your own risk.

In your photos of that PSU, I can see 3 points worth mentioning, which I have marked on this version of your internal photo:

Annotated version of OP's internal photo of the PSU

  1. As kindly commented by Spehro Pefhany, on the right appears to be a round, 2 A, time-delay (slow-blow) mains input fuse, designated F1 on the PCB.

  2. Close to that fuse, and only on that photo (not on the photo showing the reverse side of the PCB, for example) there appear to be 2 unexpected component leads or wires. This is a concern.

  3. Not yet mentioned, and very relevant since you shorted the output, is that there appears to be a rectangular, 4 A, time-delay (slow-blow) fuse on the output, designated F2 on the PCB. Obviously that should be checked for continuity (as should mains input fuse F1, but output fuse F2 is a more likely candidate for having blown, after the output was shorted as you describe).

Only replace any blown fuse with a functional equivalent, and never with a piece of normal wire. If the replacement fuse blows, than there is a further fault which will need to be investigated (or further repair attempts could be abandoned at that point).

  • \$\begingroup\$ Thank you for this answer. I am aware of the mains power dangers, I was mainly interested in learning about this subkect with the help of the community, and i do not plan on playing with live wires or execute any serious repairs on this. I do think the fuse is a very good guess (i will check if it blew tomorrow and comment results). The 2 wires on the photo are the dupont connectors at the output. I shorted the pins of this connector with my dmm while measuring voltage.. that was stupid and should have used a proper conmector \$\endgroup\$
    – JCSB
    Dec 20, 2020 at 8:38

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