Are all 5v 1A adapters all equal?

April 3, 2012 at 14:58:45
Specs: Windows 7
I sell ZipDrives second hand to the music market. A ZIpDrive takes a 5v 1A DC adapter, and typically I get ZipDrives in without power supplies. So I decided to get a bunch of 5v 1A power supplies for cheap.

If I use one with any ZipDrive, it powers it up, but it doesn't drive the motor per se. It's like the ZipDrive is getting enough power but not enough. I have a nice multimeter and it says 5.40v for the new adaptor and 5.16 for a working valid stock ZipDrive adaptor. The power supplies are identical as far as I can see.

Why is this happening?

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April 3, 2012 at 17:54:57
If it's truely capable of putting out 1 amp then it should be working. The only other variable would be polarity and you would most likely see nothing happening or possibly smoke instead of it powering up.

Can you take one of your zip drives apart? If so, plug in the power supply and power it up. Then test the voltage on the power input. If the voltage drops more than 10%, then the power supply isn't capable of it's 1 amp rating.

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April 3, 2012 at 18:05:55
NO. All power supplies lie to some extent.

Some have both current and voltage controls.

Some have only one or the other.

Some have basically no controls and use the proper device as a limiting factor.

The only way to be sure is to test both voltage and current and maybe AC component.

A Pit Bull is like a gun you can pet. And there is no safety on it.

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April 3, 2012 at 19:46:21
Are the plugs on the new adapters the same as the original zip ones? They might fit but if it's not a tight connection it might balk at supplying higher currents. Kind of like a loose battery cable on a car--the radio will work just fine but it won't start.

Just curious, how much do you pay for zip drives and what kind are you looking for?

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April 3, 2012 at 20:37:43
It's a tight fit, the specs are the same 2.5x5.5mm. These are wall-wart AC Adapters.

I look for SCSI ones, I won't pay over $20 when all is said and done.

How would you measure current (I'm a little dumb there).

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April 3, 2012 at 22:40:16
Most multimeters can test for current. The meter leads need to be part of the circuit. You might need to do something like cut one of the wires from the adapter and connect the meter leads to each cut end. But I wouldn't bother doing that. If they're not working with the drives then they must be defective. There are inductive ammeters that don't require an in-circuit setup but I doubt you have one of those meters.

Are you sure they're the same polarity (negative ground) as the original zip ones and are rated at 1 amp (1000 mA)?

I probably have about a dozen external SCSI zip drives. Most are 100 meg, at least one is 250. I use a parallel port and a USB port drive and don't have any use for the SCSI ones. If you think you might be interested I can give you can exact count on them and the SCSI cables they use in the next day or two.

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April 3, 2012 at 22:52:33
Other ratings surge current and voltage drop. Output voltage regulation under input voltage change. Ripple component. RF and other hi-frequency noise.

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April 4, 2012 at 07:34:47
The polarity is the same (neg grnd) and the adapters SAY they are 5v 1A. If the polarity was wrong the Zip wouldn't power on at all, would it?

My feeling is that these cheap adapters don't really handle 1A. They are VERY light, but of course I've seen Iomega adapters that work that are light. I might find a electronics shop in town (I live in a small town) to check.

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April 4, 2012 at 17:39:22
Without cutting the wire and putting your voltmeter/ampmeter in series, you can't really measure current. That is why I suggested testing the voltage under load by opening up the zip drive and testing it on the input. If tit drops more than 10%, it's not supplying enough current.

If the polarity is wrong, yes it probably woudn't work and possibly burn out the drive.

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April 5, 2012 at 05:18:24
This may be obvious, but if I got a 5V 2A adapter, would that guarantee it would provide the load the ZipDrive needs?

Short of taking apart the ZipDrive (which is actually not doable if you know ZipDrives), it seems that these cheap adapters aren't really 1A, more like 750ma or something like that.

So even though the Iomega comes with a 5V 1A adapter, would using an 5V 2A (counting on them to be at least 1750ma) be an alternative?

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April 5, 2012 at 05:28:56
On a power supply designed for a wide range of current, as long as the current draw is within limits the voltage should remain within tolerance.

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April 5, 2012 at 05:53:07
Right, but I wasn't talking about voltage - the adapters are all 5v and when tested under no load they display voltage slightly higher than 5v. Given a higher amperage rating on the adapter, that means the Zip won't drop the voltage given it's load, right?

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