Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I have an Acer aspire 5000. When I turn it on, the ambwer 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 3.42 amps, while the new one is 3.95 amps.

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


Edit: Ah! I got this mixed up. The old one is 3.95, while the new one is 3.42. So it sounds like from the answers so far, I shouldn't be using this new one.

share|improve this question
1  
And now that I'm looking athte bottom of the laptop, it says "19V, 3.42 A" next to "DC rating". So I'm guessing it's okay to use the 3.42A adapter, since the 3.95 was overkill in the first place. –  user13743 Jan 25 '10 at 19:51

2 Answers 2

up vote 5 down vote accepted

You should be able to use this adapter.

Current ratings on the PS are maximum allowable draw.

That is, you shouldn't connect a 3.95amp powersupply to a device that will pull 5 amps.

However, connecting a 5amp powersupply to a device that only needs 3 amps is fine (assuming the voltage ratings are the same).

Edit:

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.

share|improve this answer
    
The new one capable of supplying more current than necessary will run cooler (and should also last longer) than the original. –  Brian Knoblauch Jan 25 '10 at 20:17

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.

share|improve this answer
1  
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 Jan 25 '10 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 Oct 6 at 7:15

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.