question about amps


Old 01-16-13, 05:43 AM
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Join Date: Mar 2010
Location: USA
Posts: 12
Question question about amps

I got an old Westell DSL gateway (computer) modem from a friend, but it didn't have the power adapter. I looked on ebay for replacement power adapters and it looks like it requires one that has an output rating of 12V and 1amp/1000mA.

Now, I also found another power adapter laying around. Its actually a Westell branded power adapter and was previously for some other similar piece of equipment. Its plug fits this Westell gateway, but it has a power output rating of 12V and 1.25amps/1250mA.

Logically, I'm thinking it can't be used since it has too many milliamps. Yea, it might initially work, but will ultimately burn up the equipment at some point. Is this pretty much the case or will a 250 milliamp difference not really matter?

Also, I found another adapter laying around that while it fits this Westell gateway as well, it has a lower output rating. I think its basically 7.5V and 800milliamps. Will this rating damage as well?
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Old 01-16-13, 06:19 AM
Join Date: Jul 2012
Posts: 70
You can use the adapter with the higher amp rating (1250 mA). The rating is only what the adapter is capable of supplying, not what it would force the modem to use.

You can't use the lower rated adapter because the voltage iis wrong and the current rating is too low.

Also, before you plug in the modem to the adapter, you need to check the polarity on the plug (assuming it is a DC adapter). There should be a symbol on the adapter and one on the modem indicating whether the center of the plug is positive or negative. The adapter and modem need to use the same polarity. If the modem and adapter are 12 V AC, then it doesn't matter.

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