The normal power adaptor for a laptop is rated at 19.5 V 7.7 A.

Got another adaptor from a previous laptop that is rated at 19 V 6 A.

Is it dangerous to try and power the laptop from the previous laptop's adaptor?

Could be.

The main part may be to find out if the psu is regulated. If the original is regulated and the second is regulated then it may be OK. You should watch battery or just remove it when on AC.

They usually sell products as a direct replacement for your laptop. Are you trying to save a few bucks? A very long time ago I got in a hurry and wired a cheapo laptop ac adapter backwards. Cheapo laptops also go up in smoke. Funny as it did work for about 3 minutes.

Without direct tested voltage and current readings on unregulated then I'd not try it.

be careful to check the polarity.
that's far more likely to fry hardware.

Ok just checked polarity and it is the same.

How do I find out if the laptop's psu is regulated? It's a Gigabyte P35W v3.

Normal adaptor's open-circuit voltage 20.3 V.

Old adaptor is actually a multi-purpose adaptor that has a switch that lets you choose the nominal voltage:

Nominal 19 V -> open-circuit 19.2 V
Nominal 20 V -> open-circuit 20.2 V
Nominal 22 V -> open circuit 22.1 V

So the 20 V mode is a closer match but still... How do I find out if the psu is regulated?

I'd go ahead (assuming polarity ok, which it likely is, tip +).

The extra amperage is for charging an empty battery while max cpu etc load running!!!
So, avoid that specific situation. The missing .5 volt, 3%, shouldn't matter.

I think there's some relevant power/battery/temperature monitor apps. for Linux.

Awesome laptop!!!

Looks pretty solid=regulated, .2 is 1%

And IF you had a 3ohm 100watt 'power resistor', you could check ps volts under load

The best answer is to get the correct device.

They are sold as regulated. Once in a while it says on it.

The generic one is somewhat regulated over this other single volt model.
Regulated tend to be very close to stated power levels but only regulated means regulated.

I am only an antique hardware engineer from the time that a computer power supply was built around a 6 kg (13.2 lb) transformers, capacitors a large as peanut butter jars and rectifiers which dwarf solar charger semiconductors.

But AFAIK a couple of voltages are running around in a laptop, 12V, 5V, 3.3V and a bunch of odd voltages for the processor and memory bus which are invariably lower than 3.3V. These voltage can only be generated by DC-DC converters. From the 19V input or derived voltages.

The only drawback of using a lower voltage power supply is that when the voltage input to a DC-DC converter decreases, the current increases to keep the power constant. But we are talking here about less than 3% difference in voltage. That is well within component tolerances.

I just don't know what effect the lower current rating will have. After all the power rating is decreased from 150W to 115W. Which is 20% less. You could run into stability problems with an empty battery, high screen brightness and high processor or GPU load.

jlinkels

"
Looks pretty solid=regulated, .2 is 1%
"

That was the old generic model he had. The new one is not regulated. It is unknown what the value would be on use.

Can you buy a proper replacement for it at any cost? Why were you using the generic adjustable, original long gone? I'd get a generic adjustable before I'd use the one you mention.

for a laptop, this technically isn't a PSU, it's a charger.
the laptop gets its power from the battery, transforms it internally to its needs etc.
so much of the needed regulation happens inside the laptop.
so i really don't see how one volt more or less would make any difference there, even amperage - less ampere, it just charges slower.
granted, if the laptop's battery was dead or even absent, amperage matters more.

rule of thumb:

1. if you use a charger from another laptop, you can probably also use it for that one.
2. too little voltage = worst case it won't work, too much voltage = worst case you fry the laptop. so better too little than too much.
3. common sense applies

The generic one is powered from a car cigarette lighter socket. Could get another one with more amperage and the exact nominal voltage. That socket has a 10 A fuse though.

according to my last post, there's at least 2 things in that statement that would make me wary...
and the fuse has nothing to do with anything.

Doesn't the fuse limit the input current and therefore the power and therefore the output current and therefore the wished for replacement does not exist?

a wall socket? 10 A and how much voltage? 110? that's totally way much more than your laptop could ever handle.
the relevant numbers are on the charger.
does the laptop still have a battery that is able to sustain it?

It is a power supply or power adapter. The actual charging circuit is internal to the laptop.

For special projects I have used generic power supplies that match the laptop's input voltage and provide as much or more current as the OEM model with out problems. I agree with jlinkels that it will probably work.

Fuses only limit current if its ratings are exceeded... The laptop/power supply will only draw as much current as needed. As stated if the battery is very low or screen brightness is high etc. then the laptop will draw more and it could cause problems.

Dell power adapters have an internal memory chip and the laptop will not charge if it can not be read. I am not aware of any other manufacture that does this.