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I've lost my original power adapter, and I can't find the proper one in any of the stores currently available.

I've HP Compaq 6730b, and as per cutratebatteries.com it outputs 18.5V 3.5A. However, I've found an older power adapter I have which outputs 19.5V 4.62 A.

So, my question is: how much of a difference between those two it really is, and more importantly, how much of a risk would it be if I tried the power adapter I already have.

P.S. I know pretty much nothing about electricity/electronics.

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2 Answers 2

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You should always try to find a power adapter that matches the factory specifications.

Having said that, the charger you found should be acceptable. Voltage is the key variable. Your laptop takes 18.5V and the new charger is 19.5V. That is just a just a hair under 5% difference (18.5 + 5% = 19.425). Generally speaking, a 5% variance in voltage up or down is acceptable when in computer power supplies. Plugging in an adapter with more than a 5% voltage difference and you are running the risk of damaging or destroying the laptop. As for amps, the computer will only draw as many amps as needed. Since the replacement supply offers more amps than the previous one, you are OK in that regard. If the amperage was lower, your laptop could not function correctly, or even turn off suddenly under heavy load, due to a lack of power.

Also, be sure that the barrel plug is the correct size. There are barrel plug adapters that can change one size to another. However, I dont recommend these, as they are easily lost and the added length can make it easier to damage the female plug inside the laptop when under torque. Additionally, make sure the polarity matches. There should be a diagram on the laptop and the charger that indicates if the center post is positive or negative polarity. Similar the image below:

enter image description here

Make sure the new charger matches the polarity. If it does, you are good to go. If it does not match, you will have to find another charger, or if you are confident with soldering electronics, you could modify the incorrect polarity of the power adapter's barrel plug.

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  • Thanks for your answer, it helped a lot in understanding what's going on. One question though, isn't there a standard when it comes to making barrel plugs? I though all of them used center for +.
    – errorous
    Commented Dec 3, 2018 at 17:09
  • @Milos Unfortunately, no. Most US manufactured products are center positive. However, many Japanese products are center negative. You need to pay attention to polarity. Reversed polarity will not necessarily damage your device, but it wont work.
    – Keltari
    Commented Dec 3, 2018 at 17:12
  • This is Chinese one, I believe. This being said, if the barrel plug fits, would this be fixed by simply cutting the cable in the middle and simply reverse wires(I'm naively assuming it's using 2 or 3 wires, not coaxial cable like config)
    – errorous
    Commented Dec 3, 2018 at 17:15
  • @Milos Whoa! Slow down. First you need to check the polarity on your laptop. Is it center positive or negative? Then check the power adapter to see if it is center positive or negative.
    – Keltari
    Commented Dec 3, 2018 at 17:23
  • yeah, I understand that. I was asking what could be done should the polarity on the cable/laptop does not match.
    – errorous
    Commented Dec 3, 2018 at 19:06
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There should be no problem. The amount of amps that the current charger gives is more than enough to charge your laptop. You don't have to worry about frying your components either, as laptops have built-in regulators.

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    This is not an acceptable answer. amperage is only one of many variables involved in using a charger. Based on your answer alone, one could easily damage or destroy their laptop.
    – Keltari
    Commented Dec 3, 2018 at 17:05

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