Just wondering about the AC adaptor for a My Book. How important is the Max value?



I have a Western Digital My Book Essential 1.5Tb HDD: Model Number: WDBAAF0015HBK-NESN.

I was wondering what kind of power supply this model needs. I bought two external drives, and one was not a WD product. I did not write the numbers down like I normally do, I moved the drives when I got them out of the box, so I mixed up their cords.

I read a knowledgebase article: The drive needs 12 Volts, 1.5 Amps, 18 Watts.

I was wondering about the Max value though. On the AC adaptors I have 1 says 0.5A Max, the 2nd one says .65A Max.

I am concerned about the drives potentially failing. How important is the Max value? I tried emailing customer support, they only talked about “The drive needs 12 Volts, 1.5 Amps, 18 Watts.”. They would not touch the Max value though. And they told me that the forums would be a potential help.

Does anyone know about electronics? Or have link to a reliable site?


The max value is not important. In fact the greater, the better. Your drive will only draw the amperage that it needs, ie a 1 amp hard drive will draw 1A from a 1.5A supply, and 1A from a 2A supply. The voltage must be accurate, though. Don’t use an unregulated adapter. These have output voltages that vary under load. Unregulated adapters are usually noticeably heavier than their regulated counterparts. This is because they use an iron core transformer. They are supplied with devices that have their own internal voltage regulation, eg cordless phones.


So just look for volts amps and watts in general then. What about a lower max value?

Should I be aware of any other information or symbols on the AC adaptors?

Thank you for the reply.


Don’t go any lower. For example, don’t use a 1A adapter if the drive needs 1.5A. Similary, you wouldn’t expect 8 x 1.5V series-connected alkaline batteries to start your car, even though their combined voltage is 12V.

One other very important thing is that your adapter needs to deliver 12Vdc, not 12Vac. Also be very certain that the polarity is correct. I believe the centre pin should be positive, but that’s something that you’ll need to confirm for yourself.

If you purchase a universal adapter, then the configuration on the left in the following diagram is for a positive tip:


The one on the right is for a negative tip.