The laptop immediately turns off after cleaning, what could it be?

Question

Iron

Good day, there was such a problem. Today, my friends gave me a laptop for cleaning, to be honest, it's old, but you can still watch movies, as they say. So, I took it apart, cleaned it, wiped it with alcohol as it should be, applied a brand new thermal paste, and assembled it. I checked all the cables, and they stood still, I press the power button and it starts loading Windows, after which the black screen and it does not turn on anymore. And the following happens:
When you press the turn button, the cooler starts up for a few seconds, after which the laptop turns off spontaneously. In this case, the screen does not light up. After 20 attempts, the paver sometimes works and I feel like the hard and RAM are heating up, but the cooler and the screen are out of work.
What could it be dear?

Answer 1

My opinion is that it burned out / problem / the conders in the bp swelled up. I had 4 cases of PC failure with the same symptom, when when you press the power button, the cooler of the processor starts up for a second and immediately slows down. In the comments, you wrote that the laptop can stand in the BIOS for 2 hours and everything is fine, but when you start Windows, it immediately turns off, when you start Windows, the hard drive starts to work actively, the load on the power supply increases, it is extinguished. Try replacing the power supply and see how the laptop behaves.

Answer 2

Try if there are two sticks of RAM, then swap them.