I disconnected the shorted diode and now PSU stopped making any smoke or blowing fuses, now it just makes very quiet buzzing. The charred resistors are probably undamaged, since they both have the same value of 180 ohms when disconnected. Yes, I am also quite sure that something else must have shorted.

For the diode, I have identified it as a 1N4146, but I am not too sure, since I am not too familiar with these color coded diodes. Can someone confirm if this is the correct one?

For now, I am going to replace this diode and check the nearby components for apparent shorts. If I will be unable to repair it, then I will give it to my friend who runs a electronics repair shop.

EDIT: I must have got a quite an early production unit, since the serial number is 5191.