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I have an Acer Aspire 5000. When I turn it on, the amber power LED blinks 6 or 7 times, and no booting happens. From my Googling, it seems to be a power issue.

I tried swapping out for a different power supply from another Acer. The pos/neg charge is the same, the output voltage is 19V, but the amperage is different. The original is 3.95 amps, while the new one is 3.42 amps.

Note that on bottom of the laptop, it says "19V, 3.42 A" next to "DC rating". So I'm guessing it's okay to use the 3.42 A adapter, since the 3.95 was overkill in the first place?

Can I use this new one with my laptop, or will I need to find one that matches the 3.95 A rating better?

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You should be able to use this adapter.

Current ratings on the power supply are maximum allowable draw. This means you shouldn't connect a 3.95 A power supply to a device that will pull 5 A, but connecting a 5 A power supply to a device that only needs 3 A is fine (assuming the voltage ratings are the same).

When selecting power supplies: Match the voltage exactly. You can use a power supply with a higher rating on current (amps) or total power (current * voltage, so directly related anyway).

Do not use a power supply with a lower current rating or power rating than the original.

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  • The new one capable of supplying more current than necessary will run cooler (and should also last longer) than the original.
    – Brian Knoblauch
    Commented Jan 25, 2010 at 20:17
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Background:

According to Joule's Law:

Power = Current x Voltage


Calculations:

The old supply provides 3.42 amps x 19 volts = 65 watts of power.

The new supply provides 3.95 amps x 19 volts = 75 watts of power.


Conclusions:

Both adapters provide 19 volts, but the new adapter provides 10 watts more power.

If the laptop was running and charging with the old 65 watt adapter, the new 75 watt adapter will work.

As an added benefit, the battery may charge more quickly with the new adapter.

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    This calculation is correct, but obviously written before the question was edited. Using the lower rated power supply will work. You may (probably will) run into issues if the machine is running and charging the battery at the same time, as this is when the highest current draw occurres.
    – Brettski
    Commented Jan 25, 2010 at 19:55
  • This really depends on many factors, original 75W power brick is designed to provide charging computer running at 100% utilization necessary power to run and leave some headroom. As the power supply gets older power rating will drop, so manufacturers factor this in too. Given that you have a quality, new 65W power supply and you do not load your computer to 100% it will run just fine. For example I run mine at 65W at work and 95W (came in the box) at home.
    – Enis P. Aginić
    Commented Oct 6, 2014 at 7:15

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