Dodgy mains adaptor?

[bob_mllr]

I acquired this "Singway" power converter.  This unit uses an autotransformer to step the mains voltage up or down, depending on the position of switch, so the output is NOT isolated from the mains. But the socket side has provision for accepting an earth pin, and the mains side does not have an earth pin, so non-double insulated appliances can be used with it without actually being earthed! Also the switch is confusing - it's not plain if you are selecting 117 in and 230 out or 230 in and 117 out, which might result in 500V on the socket! Am I missing something here or is this device just plain dangerous?

[bob91343]

Apparently there is a switch to select the input voltage at either 120 or 240 but I don't see how to select the output voltage.  So what I would do is plug it in and measure what comes out with a voltmeter in each position of the switch.

[Daixiwen]

No it's completely safe, it has a "QC PASSED" sticker!

[Ian.M]

If you plug it in to a 230V supply with the switch set wrong, odds are it will let the magic smoke out.  Its an autotransformer, which will saturate and draw excessive current if overvoltaged.   One of three things will happen - it *may* trip upstream circuit protection, or if it has a thermal fuse it may trip and render it dead, but IMHO its cheap and nasty enough not to be thermally protected, and in that case it will most likely draw a grossly excessive current and burn out its windings.   Whether or not it will get hot enough to catch fire before the winding shorts out badly enough to trip upstream circuit protection is a gamble I wouldn't be willing to take!

[bob_mllr]

Probably right about the smoke, but my main concern is that the output is neither isolated nor earthed yet will accept a plug with an earth pin and so will accept non-double insulated appliances, with consequent risk of live chassis/frame.

[Ian.M]

While we are piling on the defect list, its got a nasty 'universal' socket, which is unlikely to adequately prevent some mains plugs being mis-inserted, so even if it had a ground pin on its input side, it wouldn't be safe  Its also not shuttered, but that's a minor issue compared to its other egregious defects.   

I also suspect its illegal to import to or sell in Australia.

[AVGresponding]

This is the sort of "deathdapter" that bigclivedotcom loves to tear down.

[bob91343]

After thinking this thing over, I think it may have some use.  Apparently selecting the input voltage also selects the output voltage.  So if 120 is input, the output will be 240 and vice versa.

I wouldn't worry about safety.  Just use common sense.  Make sure the switch is set properly for your mains and don't overload it.

[AVGresponding]

Regardless of the likelihood of the magic smoke escaping, the fact that it accepts plugs with an earth pin whilst not providing an earth connection makes it unsafe, as it allows Class 1 appliances to be plugged into a device that only provides for safe use of Class 2 appliances.

Many a time I've cut 3-pin 16A commando sockets from the end of festoon lighting cable where some pillock of an electrician fitted them.

[bob_mllr]

Yes I agree.,  I checked out bigclivedotcom and this is similar to some of the ones he's done, except with the addition of an autotransformer voltage converter.  The autotransformer and switch are just so you can convert up or down voltage. In conclusion a dangerous POS.

[wraper]

But the socket side has provision for accepting an earth pin, and the mains side does not have an earth pin, so non-double insulated appliances can be used with it without actually being earthed!

UK plugs of double insulated devices have a fake earth pin. You will not be able to plug any of them without a hole. As of European earthed Schuko plugs, they go just fine into non earthed sockets. So this adapter is a drop in a sea of confusion with mains plugs/sockets.

[wraper]

What makes no sense whatsoever is that this thing supposedly accepts 240V and converts it down. What's the point when it only has 120V plug?  . It's useable in this way only in combination with yet another adapter  .

[james_s]

It looks like a pretty standard travel converter, I have a couple of similar ones that I use to power old Soviet clocks. Mine aren't switchable but they're all just autotransformers that convert 120 to 240 or the switchable ones will also convert 240 to 120. They're fine when used as intended, the sort of small appliances they're meant to power wouldn't have 3 wire cords anyway. Here you don't typically see grounded plugs on anything that doesn't have a metal cabinet like a desktop computer, refrigerator, washing machine, that sort of thing. Clocks, phone chargers, most laptop chargers, lamps and such are all 2 prong with no ground. These converters are usually only rated at 50W, you'd use one to power your shaver, radio, battery charger or other small appliances while traveling to a foreign country. Now that most things are universal input these transformers aren't seen as much but they were very common back when AC adapters were all iron transformer types made for a specific voltage. My relatives who traveled a lot all had similar converters they packed on every trip. They also had triac based ones that were smaller but rated 1600W, used for resistive loads like hair dryers and curling irons.

[james_s]

What makes no sense whatsoever is that this thing supposedly accepts 240V and converts it down. What's the point when it only has 120V plug?  . It's useable in this way only in combination with yet another adapter  .

They normally come in a set that has an assortment of passive adapters that can be used on either the input or output. When you have the accessories that go with it then it makes perfect sense.

[MrMobodies]

I remembered seeing that video of Bigclive taking one apart that burnt and it had a transformer and something he said about it having a switching power supply? for low current stuff but it was set on the low current and it got overloaded.

Joke: On overload one of them might sing when the magic smoke escapes.