# Newbie AC/DC electronics question

Discussion in 'Electronic Basics' started by Jamie El Fattal, Oct 8, 2004.

1. ### Jamie El FattalGuest

I am totally lost on understanding most electronics/power
requirements, so please forgive me for the following.

I have a laptop. On the power adapter, it has the following specs:

input: 100-240V ~ 1.6A 50-60 Hz (-)---(o---(+)
output: 18.5V 3.5A LPS

I want to know if I can use this second power supply for my laptop, or
will it fry my system?

input: 100-240V ~ 1.8A 50-60 Hz (-)---(o---(+)
output: 19V 3.16A

Mostly the part I need to know is do all the numbers have to match
*exactly*? Or can I have, say, a higher Amp value and still be OK? I
guess it is mostly the output that I need to be concerned about, is
that correct?

TIA.

- Jamie

2. ### Guest

The output matters..
You _might_ get away with .5V more, and .34A less. But it's takeing a chance
so you better decide wheather it's worth it. And don't forgett that laptop
batteries with wrong electricity might blowup.. without warranties.

I did an theoratical evalutaion of my own laptop battery. And the energy inside
it is equalient to 3 kubic meters of water falling down 7 meters (approx). So
one should have respect for it.
Ofcourse it also illustrates the power difference between the electromagnetic
and gravitational forces

3. ### BruceGuest

I am totally lost on understanding most electronics/power
Chances are you would be fine using the other power supply, but nothing beats
checking with the manufacturer first. Especially with the price of laptops...;o]

They both have center positive, and the specs are very close with only a 1/2V
340mA difference, but I would definitely check with the mfg before plugging it in
to my laptop.

I doubt the mfg would ship a PS with a laptop that's right at the absolute maximum
input voltage of the laptop, so a 1/2V difference is probably a moot point. Most power
supply outputs aren't 100% what the spec says anyhow. If you measure the output
at the power supply jack, you'll most often see more than +/- a 1/2V difference.

Using one with a higher output current rating is normally just fine since the device it's
powering is only going to draw what it needs to begin with "unless it's shorted". Using
one with less may or may not work, but with only a 340mA difference, it's probably
going to work fine.

If your laptop were drawing right at 3.5A from the first one, then using one with a max of
3.16A would definitely cause problems, but even so, the original one would be getting
pretty darn hot with the laptop drawing its MAX current output rating continuously.

At any rate, I would check with the mfg first. It's much cheaper than a new laptop.

4. ### JamieGuest

its my guess you should be ok with that.
its only a .5 volt increase and most likely
will drop down a bit on load.

5. ### JajalGuest

I believe that if the second power supply is regulated then it should work
fine. A Non-Regulated power supply may be harmful to your laptop as the
voltage vary depending on the load. Assuming that your second power supply
is non-regulated then I would first check with the mfg. to see if the second
power supply can be used.