I have got a laptop that requires a power supply of 15V 3A. I have a power supply that is 15V 1.4A. Will this power supply work with this laptop? I read this on a website somewhere: "1. What's all this about? If you have a laptop but no power supply, then read on. You may be able to use a power supply from a different laptop (or even from a different products altogether). The main advantages of this are that * it might be a lot cheaper * it may not be possible to buy a specific power supply Getting it wrong could damage your equipment. This file is intended to help you know what you're doing. It is provided in good faith, but without warranty. 2. How do I know if a power supply will work safely with my laptop? You will need to find out the Voltage (/V) & Power (/W) of the laptop. For the power supply, you need to know the Output Voltage (/V) & Power (/W). If the output voltage of the power supply is less than or equal to the computer's input voltage, and its power is greater than or equal to that of the computer, then the two should be electrically compatible. Do check the polarity of the plug (see question 8) before trying it. 3. What is the rating of my laptop/power supply? Electrical specifications of computer equipment are usually written on the bottom. If there is no mention of the power, then it can be calculated by multiplying the voltage and current. i.e. A laptop which requires 18.5V and 2A has a power of 37W. 4. My power supply's voltage is less than my laptop – is this OK? Well, in theory, I suppose this could damage the laptop, but I haven't ever seen this. If it's a lot less then it just won't work. My laptop takes '19.5V', but behaves roughly as follows: < 7.5V Not enough to power the motherboard (can't use at all) < 9 V CD use not possible (causes reboot) < 10 V Hard disk use causes the screen to darken < 12 V Very little charging of the internal battery 12 - 19.5 V Works as normal except for charging the internal battery, which is slower with a lower voltage. 5. My power supply's voltage is more than my laptop – is this OK? No. If you give it too much, then something's bound to be damaged (by definition). In the best case, this is a fuse, in the worst case you've just blown up the whole computer. My laptop which is rated at 19.5V has accepted up to 20.2V for a few seconds without complaint. 6. My power supply's power is less than my laptop – is this OK? Probably not. Even if it does seem to work, the transformer is likely to overheat. If you want to try this, then check for a burning smell every so often the first time you use it. Of course, if the difference is marginal, then it might work long term without a problem – since a computer probably doesn't use all its devices (Hard Disk, CD, etc) all of the time, but this is not recommended. It all depends how much margin the manufacturer have left for safety. 7. My power supply's power is more than my laptop – is this OK? Fine. This is the most your power supply can manage, so the higher, the better. 8. The plug doesn't fit. What do I do? Pay a visit to your local electronics store. Expect to pay about $1-$2 each for a suitable plug and socket with which to make your own power jack adaptor, or buy an off the shelf one if they've got one. Be certain to check that positive and negative are the right way round! AFAIK, there's no international standard on this, but the positive pin is usually in the middle, I think. 9. Can I use one transformer for more than one device simultaneously? In theory, yes. If you have a laptop rated at 35W and a printer rated at 15W, you'll need a 50W power supply to run them both at the same time. So, this means one from some other piece of equipment. If you've got that many transformers knocking around, then you're probably up to the task of wiring the things in parallel yourself, so go ahead and try it." The voltage matches but I am unsure about the A? Will it work? Thanks Alex

Well you have all the information there to work out if it will work. Item 6 applies. You will burn out the power supply if the current demand is greater than 1.5 Amps which it probably is if the manufacturer reccomends 3 Amps. Stuart

You might even damage the laptop. You need a 3 amp power supply.

Should have said `at least' a 3 amp supply.