The locking action is achieved through the interaction of three components. The cap provides a structural foundation and two notched posts on the left side for the plastic spring to slot into (purple arrow). The two prongs are injection-molded into a single unit with the cam detents and top of an internal contact showing at the bottom. Then, there's a plastic spring with the cam follower molded into it on top (green arrow) providing the snap action.
It's a simple and effective solution.
First Peek At The Internal Construction
Nothing is left to chance with internal packing and clearances. The low-voltage output PCB is held in place vertically at the top by a plastic frame, which shields it from high-voltage components in the bottom half and maintains the spacing for the two contact arms to the prong pins. Very little space appears to be wasted, judging from this angle.
Based on how small pieces of plastic were ripped off either side of the seam at different locations, I suspect that solvent-based welding was used here.
At this point, I’m just glad I managed to pop the PA-U32 open with only a few scuffs and a slightly bigger crack at the LED hole.
Assembly – Back
With the whole module now out of its enclosure, we can see the neat little package in more detail.
Up top, we have the output board sitting inside a plastic frame, which provides separation between the board and transformer underneath.
Only those two double-insulated wires connect the output board to the rest of the adapter. They shoot straight up from the winding to the output board.
Assembly – Left Profile
On the left profile, you can see how the plastic frame covers both input capacitors and provides a "shelf" under the USB connectors to separate them from the transformer underneath. Should anything catastrophic happen on the high-voltage side, there is very little chance of electrical current finding its way to the output board with so many barriers and so much distance in-between.
To the left, you can also see one of the plastic tabs going inside a contact arm.
Assembly – Right Profile
The opposite view prominently features the transformer, which occupies most of the adapter’s depth and half of its height. In front of the USB connector, below the filter capacitor, we also spot the easy-to-miss power indicator LED.
Assembly – Top
Viewed from up top, the transformer appears to account for roughly half of the high-voltage board's space. Its only other major visible component, aside from the capacitors, is a surface-mount input fuse.
Assembly – Front
From the front, we can see that the input capacitors come from Asia’x. These are poorly documented. Hiding between the capacitors and transformer is a small MOSFET, which does the heavy lifting.
Again, there's not much space going to waste.
Based on the partial model number visible from such a steep angle, along with my search results for "05N65," the power switch appears to be a TO-251 N-channel MOSFET rated for 5A and 650V.
None of what I found matched the logo in the middle. But among the manufacturer specs I looked at, RDSON ranged from 0.9Ω to 2.4Ω.
Assembly – Bottom
With most of the high-voltage board’s top occupied by the transformer and electrolytic capacitors, much of its magic gets shuffled to the bottom in surface-mount flavor. The two-prong contact arm resides at the bottom of the board, its right-most prong going through the fuse before reaching the rectifier in the bottom-left corner. DC voltage then goes through the electrolytics along the left edge, the primary-side sensing resistor, mains-side switch, and transformer primary in the top-left corner. The other components are start-up resistors, snubbers, and primary-side sensing circuitry for the SOT-363 controller in the top-right corner.
After seeing the generic ETL listing, I am a little surprised to find a custom-branded PCB in there.