I have several "old" Thinkpads. Recently I came across that Type-C PD mod to replace charge port with Type-C one. Description said:
Please pay attention what you order because normally your laptop identifies the charger by an ID pin.
Also mentioned video explains some details of making that mode and pays attention to ID pin proper resistance "simulation".
I wondered before what that pin in the middle of a plug was for. I've fixed several of my old chargers worn plugs with plugs from aliexpress, I've found they have only two wires so I soldered them, no extra wire for ID pin - and they work fine charging my old Thinkpads, chargers differ by wattage only, volts are same for them as far as I saw. What does that pin really add for laptops charging? Why chargers work w/out it when video explained its importance?
I've tried to measure resistance with multimeter as explained in the video (ground to pin). For 65w with original round (older) plug it: ~10 kOhm (video claimed for 65w resistance is ~ 286 Ohm, I was surprised - hypothesis is that video was about newer square one), for 45w newer square one ~110 Ohm, for 90w round to my surprise nothing (broken wire?). For power supply extended with aliexplress cord/plug resistance was infinite - my guess pin in the plug is just not connected to anything. Also I have round-to-square adapter - separated it measured ~ 550 Ohm - that could mean it has resistor and by comparing with other square ones: video ~286 for 65w, ~110 of 45w mine, I guess 550 Ohm supposed to signal high power available (not safe?).