AC or DC

[p.mc]

Hi

I lost a power supply for an external HDD but I do have an AC-DC voltage adapter with the options of 0 - 12volt and Positive or negative tip switch. The external HDD needs a 12v DC current but I don't know wether to switch it to+ tip or -tip. The HDDs power input shows (DC IN, this has a straight line below "DC IN" and a broken line under the straight line)

Could someone with electronic knowledge advise me please?

The manual doesn't show any details or parts list, but I suppose the adapter will do the job.

[F Murtz]

It would be dc and if you look at the drive there is probably a little picture near the socket which is like a C with a dot in the centre which are marked plus and minus. if the dot is plus then the centre contact is positive

[Roger R]

My Seagate Ext HDD has the tip +

The symbol indicates it's DC.

My Seagate Ext HDD desktop size unit is 12V at 2 Amp rating.

Roger R

[NT]

You dont really give enough info yet, but the chances are such a supply would kill the HDD. HDDs need a regulated psu, and most such things are unregulated.

NT

[Dave Plowman (News)]

Most of these universal PS won't supply enough current for an HD. What does the PS say it can supply, and what does the HD take?

[Dave Liquorice]

Aye like tip pos or neg. Others have described the symbol for that but as it's not mentioned I suspect it might not be there.

The broken line under straight line I take to mean smoothed but not regulated. (How do you google for summat like that?). The regulation being done in the housing along with the derivation of the +5v rail.

Best bet would be for the OP to google on the maker/model number of the HDD and see if the required information can be found out there.

[Andy Dingley]

Internal HDDs don't use these concentric plugs

External HDDs that use this connector don't need precise regulation.

if it was mine (it would already have the connectors written on it, and the name of the gadget written on its matching plug) I would pull the case off and work out the polarity from the circuit board. Otherwise it's more commonly + on the centre or tip, but that's a risk of killing it if you are wrong.

[Roger Mills]

Be careful! There are *four* parameters which need to be right - otherwise the HDD won't work, or might even suffer damage:

1. Voltage
2. Stability - whether or not regulated
3. Current rating
4. Polarity

If you use any old power supply without knowing what you're doing, chances are that at least some of these parameters will be wrong.

The input to the HDD should have a diagram with an indication as to which - centre or outer - is positive.

Regulated and unregulated supplies have slightly different connector sizes to prevent an unregulated supply being accidentally connected to something which needs a regulated supply.

Make sure that your substitute supply can deliver sufficient current - probably at least one amp - maybe 2 - required.

[Dave Plowman (News)]

Surely it would have an internal PS since an HD needs both 5 and 12 volts?

[chris French]

In message , "Dave Plowman (News)" writes

a;ll the external drives I have used have had an external PSU and the power connector uses a 4 pin Din plug to supply the 12V and 5V.

Though there is no fixed standard for the pin assignments

[Dave Plowman (News)]

That would make sense to me - either have the PS external, or a wall wart supplying AC and the DC part internal. But it would not seem to be the case here.

[Roger R]

Power adaptor units come in two basic types:

1. Older types utilising a transformer that may or may not be well regulated.

2 .Newer types using 'switched mode' techniques, often better regulated.

Both types are about the same size but the switched mode types are significantly lighter than the transformer types.

All the external desktop HDD's available here use the switch mode type unit.

I suspect from your description your adaptor is the transformer type; the sort of thing sold in Maplin's. When customers say they have lost their HDD power supply Maplin's advice is get another from the drive manufacturer. They don't sell them and presumably don't recommend their own power adaptors.

If you value the data that may be on the drive I wouldn't take a chance using your adaptor, but would advise getting the right part from the manufacturer, even though that means delay and expense.

Roger R

[D.M.Chapman]

Most of the ones I've got here are single power connector - 12v 1.5-2.5A.

Mainly Western digital and samsung. I do have a Lacie here that has a

4 pin psu but that seems to be the exception not the rule.

Do we know what model the OP has?

Darren

[p.mc]

Hi all

I sent off for a replacement part but it's not official, although it states for WD Essential HDD.

Thanks for the input

[Ian Stirling]

I've seen one that has a 12V adaptor, and an internal 12->5 SMPS.