Plug in power adapter ampage question


Old 11-14-06, 05:02 AM
Thread Starter
Join Date: Nov 2006
Posts: 2
Plug in power adapter ampage question

I have a device that requires 12V 1.7A and the adaper has failed (again, I already RMAd it once but its now out of warranty) however I have a similar adapter rated at 12V 3A and I'm assuming that if I use it, the 1.7A device will only draw what it needs from the 3A adapter and everything will be fine using it in place of the old one.

Seems sense to my hobby electronic experience but I wanted to check before I did it...we dont know what we dont know

Thanks for the help.
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Old 11-14-06, 05:34 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Maybe, maybe not.

Some cheaper adapters do not provide the proper voltage unless the current draw is sufficient. Drawing significantly less then the stated current MAY cause the voltage to be too high and damage the device.
Old 11-14-06, 07:32 AM
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Join Date: Nov 2006
Posts: 2
thanks for the reply racraft, I didnt know that, however wouldnt that be something that can be checked with a multimeter and a load? What kind of load would be recommended?

Thinking for a second, what about no-load conditions? If that was the case then wouldnt the adaptor be kicking out unusually high voltages with just the meter across it?
Old 11-14-06, 07:50 AM
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Join Date: Feb 2006
Location: Boston, Mass.
Posts: 27
Test under load

You can test the power supply under load using an 8 ohm, 20 watt resistor (Radio Shack has these, stock number 271-120 ). E=IR says the resistor will draw 1.5 A and 18 watts at 12 volts, which is close enough to your device's specs to show how the replacement power supply will behave at the lower current draw.
Old 11-14-06, 08:25 AM
Join Date: Sep 2002
Location: welland ontario
Posts: 5,678
As long as the polarity is correct I would try it. Measure the voltage when it is running your device. Most of the units that use those type adapters don't require that precise a voltage. They usually have quite a wide range of acceptable voltage.
check the name plate on the device. I have a GPS that use 8-35 volts.

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