Using a laptop power supply (not to arduino); will it work

I need a regulated 5v with a lot of amps. I have a 19v 3A laptop power supply (I'm assuming SMPS for absolutely no reason) and I'm under the assumption that I'll only have to modify some resistors to change the voltage. Am I losing potential amps (probably a stupid question) because they are proportional in ohm's law, or will it magically draw more current from the AC? If I'm on track for an experiment, is it safe physically?

If all of that was off-the-wall bull, how can I get my regulated high-current power? I have tons of DC adapters, how do I tell if it's regulated? Are there components I can harvest to regulate it out of random stuff I probably have? Sorry about the obvious "buy one" as I can only comfortably afford free and my entire project is being held up by the power supply.

What is a lot of amps? I think that 10A is a lot, a truck driver would say that 200A is a lot.

You can not change the switching power supply just like that. Those are optimized for 19V and don't have a universal circuit inside that can do any voltage. Those power supplies have often a closed box (the plastic is 'glued' together with ultrasound). You would have to break the plastic to be able to open it.

A DC-DC converter outputs a regulated voltage. It is noisy and might influence analog signals, but it is regulated.

For a lot of amps, you could use a power supply for a computer. You need to activate the sense wire, and you have to measure the output without load. Some of those power supplies don't like it when there is no load.

Thank you. I’ll eventually be pulling ~5A, but for now 1.5A will be enough. DC-DC conversion is an interesting thought but if I use a car charger, would I have to use an AC-12vDC converter? Also, I’m gonna waste a fair amount of electricity when it’s idling, right? A desktop power supply would be ideal but I’m not testing/coding any analog signals yet, so the DC-DC converter should get me right on through. Thanks again!

A char charger for lead batteries can be regulator or unregulated rectified. A DC-DC converter that can handle an input of 30V should be okay.

19 v at 3a. Its almost certainly switchmode.

Do not even consider adapting it .

Use a 5 v reg will give 3A with loss.

What current do you NEED.

A pc supply power supply will give 5 v at huge amps , at fairlymlow cost, probided you waste some power wasting energy to meet minimum load requirments.

I use one at 40 A for electroplating.

UBECs like below might be of interest.

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR12.TRC2.A0.H0.Xubec&_nkw=ubec&_sacat=0&_from=R40