Is it an RoHS (lead-free) board, by any chance? 😀

I use a Weller WS-81 station. Not cheap, but excellent quality. 80W (though I only have a 50W iron with it), accurate temperature control from 150 to 450°C, and tips are available in many sizes and shapes.

Probably a combination of RoHS solder and the fact that the 4-pin power socket is connected to a large ground plane that makes the whole board act like a heatsink.

You don't really need a different soldering iron, you need a heat gun. You can get fancy temperature-controlled hot-air rework units, but a cheap heat gun from a hardware store is adequate for this sort of task. Use the heat gun to preheat the back of the board for several inch radius around the connector (get the area up to about 100C, give or take, making sure not to hold the gun too close the board), then take your iron and apply a bit of fresh leaded solder to the pins of the connector (which will lower the overall melting point... you'll be able to see when the new solder mixes with the existing stuff). Then try desoldering it, preheating the area again if necessary. It should come off pretty easily.

Hmm, never noticed that before - it's a no-name board, but there is a sticker that says "RoHS Compliant". So, this is a sign to tell me that I'm going to need a bigger gun? 🤣.

Anything else I need to look out for when purchasing a heat gun? Would I need additional accessories, tools etc?

I have some Aoyue 968A+ whatever combination station that I quite like working with. Together with a cheapy heatgun to preheat a board you can get most stuff desoldered fairly easily. Those multilayered boards just need a lot of heat.

Well, if you were trying to actually solder with it, like for doing SMD work or whatnot, then yeah, you'd want a proper hot-air soldering station with temperature control and various different interchangeable tips and such.

But for just preheating an area to make it easier to melt solder with an iron, then you don't need anything fancy at all. Just go to whatever store in your area that carries dodgy Chinese tools, and ask for a heat gun. Here in the US we have Harbor Freight stores, where I got this. It's every bit as good quality as the price would imply, but it works. Hell, even a hairdryer on the high setting might do the trick. The idea is to warm up the area so not as much of the heat is being sucked away from your iron tip... it really is as simple as it sounds.

Okay, thanks everyone. I know what I need to do. Cheers.

i put the iron up to the joint then added normal old school leaded solder, that in turn starts melting the silver solder. also the conditioning of the iron tip is absolutely paramount. i never touch them to wet sponge or dip them in flux, i only add more solder to the tip and scrub it in metal soldering sponge then add some more solder but, be careful how much solder is loaded on the tip affects accuracy but, also how well it conduct and heat and how well/fast it melts the solder.