question about amps

903 Views 6 Replies 3 Participants Last post by bernie963, Jan 16, 2013

mcf57

Discussion Starter · Jan 16, 2013

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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bernie963

· #2 · Jan 16, 2013

the first one should be fine. the voltage is the same and the current listed is the max. the modem will draw what it needs (in terms of current) at the rated voltage.

there are two other factors which are more important than your question.

first, is the output of the supply ac or dc? what is the required current Ac or dc. they must match.

second, if the current is dc, then the polarity must match on the power supply and the modem. if it is ac, then it does not matter.

bernie

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md2lgyk

· #3 · Jan 16, 2013

The 1250 mA is just the maximum current the adapter is capable of supplying. The modem will only draw the current it needs.

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mcf57

Discussion Starter · #4 · Jan 16, 2013

bernie963 said:
first, is the output of the supply ac or dc? what is the required current Ac or dc. they must match.

second, if the current is dc, then the polarity must match on the power supply and the modem. if it is ac, then it does not matter.

I'm not sure what the output supply is (ac or dc). I'm at work now and don't have it in front of me, but will this info simply be stated on the power adapter when I get a chance to look at it?