Strange problem. Got a computer that does not work sound (sound card is not in the list of devices). Using it for some time I heard the start-up sound when I started the system. The sound worked, but when the system finally started up on the login screen, I realized that the keyboard and trackpad do not work. An external keyboard and mouse work well. After resetting the SMC, nothing changed, but when I reset the PVRAM using an external keyboard (it doesn’t work with the built-in keyboard), at first I did not hear the sound of the system start, after which there was a black screen for a very long time (I waited for about an hour, there was no result) . Leaving the problem for later, I left the laptop off for the night. In the morning I found that the computer turned on as usual, the sound did not work, but the keyboard and trackpad started working again.
What could be the problem? Macbook Pro 15 "Late 2013. I start the system from an external SSD (there is no internal one). But as far as I know from the previous owner, the problem is also relevant to the internal SSD.
Disassembled the computer, everything is connected inside, all the cables and wires, the battery has recently been replaced with a new one.