Why does a 220V power supply work without connecting to a PC and without a "jumper"?

Question

Do it yourself

There is a power supply for the PC. An old lady, so to speak.
Disconnected from the PC, you insert 220V power into it and switch to the toggle switch and it starts working. No "bridge".
What is this strange disease? Is it possible to find out what is the reason?
I took it apart, cleaned it of dust, looked at the radio elements (it seems everything is in order. Usually, if the capacitor is swollen or something is broken, then I can fix it). In general, visually everything is fine.
The only thought that came to mind is that something closes (dust, goat, bolt) the green and black wires on the board itself, because. almost impossible to get there.
A couple of photos, maybe someone will poke a finger at something:

Answer 1

In the photo with the printed circuit board, I did not find the area with the power supply controller chip. Most often it is TL494 or the same type K7500, it looks like two parallel rows of 8 pins on the board. As a rule, this controller is only responsible for voltage stabilization (averaged over all output channels) by controlling PWM, and for soft start, and it rarely dies. And the on / off function, monitoring the current overload and issuing the Power good signal is handled by another microcircuit, which on the board looks like two rows of 4 or 7 legs. It is also not noticeable on the board. In your case, most likely she and / or the harness around her died.
There are power supplies on other controllers, more modern ones, in which the above functions are combined in one chip. Diagnosing them is much more difficult, and, on the contrary, easier to repair, since all repairs are limited to replacing this chip. Despite this apparent simplicity, in my practice I personally do not repair such power supplies, but send spare parts for other power supplies to donors. What I advise you, if yours is like that.