Please help me use a 120V scanner in Australia

October 31, 2009 4:50 AM

Can I safely use this step down voltage converter with this scanner?

The scanner's AC adapter specifies an input of:
100-120V~
50-60Hz
1.0A (don't know what this is)
40W

My friend's dad said any step down converter rated at 60 Watts or higher will be fine (a lower watt output might cause the scanner to overheat). Is this the only concern?

In hindsight, I should've purchased the 240V version but now that I'm here I'm prepared to fork out around an extra $100 to get my scanner working (ah the things we do for film!). I have seen devices ranging from $9 to over $100; is there a difference in reliability and which is suitable for me?

I live in Australia.

posted by quosimosaur to technology (12 comments total)

You might be able to get the correct power supply from Epson Australia for about the same price as a step-down converter.
posted by scruss at 5:15 AM on October 31

1.0A (don't know what this is)

It means 1 ampere. The converter you linked to is rated at 60 watts, which is only half an amp at 120V. So no, it won't work.
posted by jon1270 at 5:42 AM on October 31

With a second look at the scanner's specs, I'm not sure what to make of them. 120V, 1.0A and 40W don't agree with each other, so I'm clearly out of my league on this question.
posted by jon1270 at 5:51 AM on October 31

The scanner's electrical specifications are a bit strange, in that they give several different rated power values.

Scanner power consumption is 17.5 Watts (Operating, with ADF)
Scanner input power is 24.0v*1.3 A = 31.2 Watts
AC adapter output power is 24.0v*1.3 A = 31.2 Watts
AC adapter input power is 120V*1A = 120 Watts.

Now, there's two things that explain that. The first is, if you've got a product that needs 20 watts and you supply it with a 30 watt power supply, it will work fine, drawing only as much power as it needs - just the better power supply will cost a bit more. So it's not uncommon for products to come with power supplies that are bigger than they need be. The other explanation is inefficiency. You'd expect a bit of inefficiency, but not so much that you'd need a 120 watt power supply to run a 17.5 watt scanner; anything that inefficient would get dangerously hot, so no-one makes anything that inefficient.

In summary, it's likely Epson just supply a more powerful power supply than they could get away with; you should be fine with the product you've found on ebay.
posted by Mike1024 at 9:09 AM on October 31

Yes, the converter will probably do the job. The scanner specs from Mike1024 show that the scanner only uses 17.5 watts and the converter you are considering can output up to 60 watts. It has a thermal fuse so the worst that would happen is that it may shutdown if overloaded. But as scruss suggested, why don't you call Epson in Australia to see if you can get the proper power supply.

Either solution should do the job.
posted by JackFlash at 10:24 AM on October 31

It looks okay. I'm having a hard time imagining what the scanner might be doing to need 120W -- I'm going to agree with those above who say that the scanner is using a fraction of the power that the supply is rated for (this is not a bad thing for anyone but Epson, who are paying extra for a beefier supply).

The voltage converter appears to be the right type (a transformer). The wrong type is usually labeled "for hair dryers, irons, and other heat-producing devices" and just has a rheostat inside. You can tell the difference because the transformer type is about a million times heavier than the rheostat type.
posted by range at 12:11 PM on October 31

What's happening here is that the scanner's power supply does not have power-factor correction (PFC, google it), which means the current it draws is not in phase with the line voltage. That means that the scanner draws a lot more current than you would expect from its power consumption. In other words, its input impedance is complex rather than real.

Given they say 1A and 110-120V, you want a step-down converter capable of 120VA. Note that this is NOT the same as 120W, due to poorly-designed corner-cases like this power supply. If you buy a transformer-style step-down thing, it will say either 120VA or 120W on it (or higher) and it will be fine. If you buy an electronic step-down, it may well not be fine at all, regardless of its power rating, due to the lack of PFC on the scanner's supply.

If the scanner has an external power supply brick, a much better option would be to replace that with a 240V version that has the same DC output voltage and with a rated DC current that is higher than what the scanner needs.
posted by polyglot at 8:26 PM on October 31

I wasn't able to learn the difference between a transformer-style step down thing versus an electronic-style step down thing using Google. But anyway, I will see if I can do this the proper way by ordering the 240V AC adapter from Epson Australia.

I really appreciate all the help I've been given. Thanks!
posted by quosimosaur at 2:47 AM on November 1

What does the power brick say about its output voltage and current? There's a good chance it's pretty generic and you could get one from Jaycar or Altronics or whatever.

In terms of transformer-vs-electronic, the transformer ones are heavy because they're full of iron, the electronic ones are really light. A compact toroidal 120VA transformer weighs most of a kilogram last I checked, and a traditional E-core one will weigh about 2.5kg. You can buy them locally but that's not necessarily the cheapest option.

If (for example) the brick has a 12V output, this sort of thing will do what you want for a lot less.
posted by polyglot at 2:04 AM on November 2

The power brick outputs at 24V and 1.3A.
Between these two values is a symbol that looks like '=' except the bottom line is a dotted line separated into 3 dashes.

I'll give Epson a call tomorrow while I'm at work and I might also visit Jaycar after I finish up. Thanks again, polyglot!
posted by quosimosaur at 5:55 AM on November 2

The dotted = sign means direct current (DC). The Epson supply is your best option if it's available and affordable since it will just plug in and you know it will work. If you can't get one then this will do the job for you, electrically at least. Altronics is likely to have an equivalent but their website seems down right now.

The hardest part of using the 3rd-party supply will be making sure the plug is compatible since it's unlikely to come with the same one that your scanner requires. You may need to transplant the plug from your old Epson supply to it, and it's critical that you get the polarity right - easy for someone familiar with electronics. Do you know anyone who tinkers with this stuff? Got any tame electrical engineers or technicians nearby?
posted by polyglot at 5:15 PM on November 2

I'm ordering a power supply from Epson. I've been quoted about $40 inc. shipping from an Epson spare parts supplier which sounds fairly reasonable considering the options.

My friends and family are all trained in useless fields. Hopeless fuckers. But then I'm no better.
posted by quosimosaur at 3:15 AM on November 4