Is there any way to check if a power supply is auto switching multi-voltage input (120-230VAC) with an output of 6VDC? The supply is an electronic power supply (not transformer based) but has absolutely no information on it. I do not want to fry it by trying 230VAC, as it does work on 120VAC. Thanks.

  • \$\begingroup\$ If there are no markings on the case and you don't know where it came from... probably not. \$\endgroup\$ – Trevor_G Apr 17 '17 at 19:33
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    \$\begingroup\$ open the case and look at the parts inside. probably easier to just replace it. \$\endgroup\$ – Jasen Apr 17 '17 at 19:38
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    \$\begingroup\$ "The supply is an electronic power supply (not transformer based)..." - Switching power supplies like that are also transformer-based. No transformer means no isolation between mains and output. \$\endgroup\$ – marcelm Apr 17 '17 at 20:22
  • \$\begingroup\$ @marcelm not that there aren't such horrible, horrible devices... Though they luckily can't legally be imported into the EU nor the US as consumer devices. \$\endgroup\$ – Marcus Müller Apr 17 '17 at 20:24

There are two ways to do this check; one, of course, is to examine the power supply for a label. Most AC-input power supplies are well-labeled so that the user does not need to guess how to safely plug them in. It may be necessary to examine the very fine print, closely. It is sometimes necessary to ensure that a switch or jumper connection is made, on some older power supplies, to select a voltage range.

The other way, is to reverse-engineer the power supply, by examining the internal circuitry. Sometimes the power connector is suitable only for one national standard power connection, and examining the plug is a very strong hint.

Checking the output power is easy; just apply a voltmeter while a suitable load (usually a resistor) is attached. One would use the voltmeter, also, before touching any metal on an unlabeled box that accepts AC power, to ensure you don't get a shock.

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  • \$\begingroup\$ The question does state that the transformer has no markings on it. So why suggest that he checks the labels? RTFQC \$\endgroup\$ – Gineer Apr 18 '17 at 7:47
  • \$\begingroup\$ @Gineer Very fine print, pale grey-on-white, molded lettering, are not easy to read. I've seen a variety of power supplies, but none without some labels, somewhere. \$\endgroup\$ – Whit3rd Apr 18 '17 at 11:43

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