After cleaning the computer, it does not start at full power, what's the matter?

Question

Iron

In general, the thing is, the computer was very noisy and I know that it has not been cleaned for a long time and the thermal paste on the processor has not been changed. I disconnected the power supply, removed the cooler and processor, removed the video card, then removed the motherboard. I cleaned everything from dust, applied thermal paste and put everything in place. At first, the system unit didn’t turn on at all, then I realized that I didn’t put the chips from the power buttons correctly, rearranged them correctly, then the system unit turns on, that is, the fans on the power supply and the processor spin, it makes noise but very quietly, the lights on the motherboard glow. But there is nothing on the monitor, the monitor, when connected to the network, shows the inscription "energy saving mode" and switches to it accordingly, when the cable is disconnected from the monitor that goes to the system unit and is connected there through an adapter, But if you connect to the adapter but do not insert the adapter, then it does not write to check the cable and if you insert the same thing. And now the system unit is working, well, everything is spinning, it makes a quiet noise, not like at startup usually, at normal startup (before cleaning) there was a single not a squeak, but something like it, and after that it already started to work (well, make noise) and on the monitor there are already inscriptions amd and so on, that is, it turns on. And now I press the power button, it starts, but without this sound (single squeak), but it just works as if at idle and does not show anything on the monitor, respectively. But if you connect to the adapter but do not insert the adapter, then it does not write to check the cable and if you insert the same thing. And now the system unit is working, well, everything is spinning, it makes a quiet noise, not like at startup usually, at normal startup (before cleaning) there was a single not a squeak, but something like it, and after that it already started to work (well, make noise) and on the monitor there are already inscriptions amd and so on, that is, it turns on. And now I press the power button, it starts, but without this sound (single squeak), but it just works as if at idle and does not show anything on the monitor, respectively. at a normal start (before cleaning), there was not a single squeak, but something like it, and after that it already started to work (well, make noise) and the monitor already had AMD inscriptions and so on. And now I press the power button, it starts, but without this sound (single squeak), but it just works as if at idle and does not show anything on the monitor, respectively. at a normal start (before cleaning), there was not a single squeak, but something like it, and after that it already started to work (well, make noise) and the monitor already had AMD inscriptions and so on. And now I press the power button, it starts, but without this sound (single squeak), but it just works as if at idle and does not show anything on the monitor, respectively.
I can send videos and photos of how I took it apart and how it all works for me, I just don’t know much about hardware myself. I forgot to add, I decided to check if the power supply was damaged, I turned off the computer but did not disconnect it from the network, I took out the cable that goes into the socket from the system unit, put it in, then removed the bolts from the power supply mounts, took the cable in my hand to shift it and it slammed , it smelled of burnt rubber and there was black soot near the connector that is inserted into the system unit, but I can’t find external damage, the cable does not work after that. Maybe he didn’t work well before the pop, that is, he started the power supply but not completely, or somehow it didn’t work and slammed as a result?

Answer 1

Check the power connection to the motherboard - you may have forgotten a separate wire to 4pin ....
Check the power wire to the video card
The monitor writes the same information, just in different words in essence

Answer 2

First of all, I would look at the legs of the processor, maybe they are bent, it happens when you remove the cooler, you can pull the CPU out of the socket, you can even tear off the legs. Symptoms are similar

Answer 3

Anything could be the problem. The motherboard is still with IDE, it is already 15 years old.
It's hard to say what's wrong.