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I've searched for an answer to this question, perhaps with the wrong terminology.

I have several little DIY boards around the house with a small on board 3v3 regulator. I feed these with old 5v phone chargers. Lately I had 3 of them break, all of these were genuine Samsung brand 0.7A USB chargers (older type where the USB lead is permanently connected to the housing, before they started making them detachable).

And with break i mean, the samsung supply stops supplying 5v, its more like 3v now, both open circuit and under load. My boards stop working altogether as well (although hooked up to my desktops 5v they still work fine).

Now the question is, are these switching power supplies breaking of old age ? or aren't they designed to supply a comparatively small load of 20mA 24/7

Any input would be appreciated!

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closed as off-topic by Andy aka, Marcus Müller, brhans, PeterJ, Dmitry Grigoryev Jun 28 '17 at 16:29

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Andy aka, Marcus Müller, PeterJ
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Questions about "consumer electronics such as media players, cell phones or smart phones, except when designing these products or modifying their electronics for other uses" are off-topic. See this: electronics.stackexchange.com/help/on-topic \$\endgroup\$ – Andy aka Jun 28 '17 at 10:21
  • \$\begingroup\$ @Andyaka but this isn't really about the consumer electronics listed per-say, but more about whether the switching power supplies that just happen to be in the charger of such an item in this case are susceptible to degradation over time? \$\endgroup\$ – Trotski94 Jun 28 '17 at 10:46
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    \$\begingroup\$ I'm confused. A 3v3 regulator should deliver "more like 3v", i.e., it should deliver 3.3v, not 5v. \$\endgroup\$ – Pete Becker Jun 28 '17 at 13:11
  • \$\begingroup\$ @PeteBecker - "I'm confused. A 3v3 regulator should deliver "more like 3v", i.e., it should deliver 3.3v, not 5v." As I understand it, the OP is saying that his 5V USB power supplies, after becoming "broken" from long usage (for unknown reasons) only produce "more like 3v" (in other words something around that value - did you interpret the OP as saying "more than 3V"? Of course that (something around) 3V going into any kind of linear 3.3V regulator (even LDO) won't produce 3.3V at the output :-( Hope that helps explain the OP's description from someone else's viewpoint. \$\endgroup\$ – SamGibson Jun 28 '17 at 14:22
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    \$\begingroup\$ @SamGibson -- good point; the problem is that in "Lately I had 3 of them break", the "them" is ambiguous, referring to either the DIY boards or the "old 5v chargers". You're probably right that it's the latter; that fits better with the rest of the words. \$\endgroup\$ – Pete Becker Jun 28 '17 at 15:09
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Most probably some of the output electrolytic capacitors have failed due to aging. This results in large voltage ripple, which messes up the feedback and average voltage measured with a multimeter drops to 3V, while maximum voltage still would be about 5V if you look at it with an oscilloscope.

You have a big chance to repair these chargers successfully just by replacing the old caps with new. Be sure to use high temp (105C) and LOW ESR type capacitors. Be aware that there is High Voltage on PCB. After unplugging the adapter from mains you should wait long enough for it's input capacitor(s) to discharge.

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