Electronic – Can anyone please help me identify this component, SMD (R40 515 Z5J)

This looks like a potentiometer with a built in on-off switch on the back.

When you either push on the knob or turn it to the end of it's range does the resistance between A and B change from infinite to 0 ohms? If so, you have confirmed that it is a switch.

The resistance between 1 and 3 should be fixed and between 1 & 2 (or between 2 & 3) vary as you turn the knob.

These are (were) commonly used as combined volume controls and on-off switches on radios before the digital age.

In response to the comment.

Since you measured an exponential change in resistance you have what is known as a logarithmic taper potentiometer. The other type is a linear taper. Logarithmic taper is used for volume controls since human hearing does not respond linearly but rather on a decibel scale.

If you measured across 1 & 2 instead of 2 & 3 you would have perhaps found the switch as "on" when the potentiometer is "on" as you put it. Looked at another way, the resistance across 1 & 2 will increases as the resistance across 2 & 3 decreases. In fact the resistance between 1 & 3 should remain constant as you turn the knob. Also for any place you put the knob, if you add up the resistance between 1 & 2 with the resistance between 2 & 3 that total should equal the resistance between 1 & 3.

The part is connected to pin 5 of the USB connector, which is the 5V supply from USB. It is most likely to be a fuse: either a PTC resetable fuse or a non-resettable fuse. Its marking are consistent with a SMT fuse, although to understand the marking you would need to know the manufacturer of the fuse. It is unlikely to be an inductor or ferrite bead, since those parts are usually unmarked.

After the fuse is a diode of some sort connected between the 5V supply and Ground. This is probably a TVS diode to protect the device against voltage transients.

If you follow the PCB trace it then passes through part which is probably a ferrite bead which is used to reduce EMI emissions. SMT ferrite beads are usually unmarked.