How do I desolder alps? Is there a guide to avoid doing it wrong?
If the legs are not bent over, they come out pretty easily.
When the legs are bent over, it becomes a nightmare. I have not mastered the technique, and have at least 2 wrecked Northgate 101 PCBs to show for it, but you need to suck up as much of the old solder as possible, then melt whatever remains with one hand while gently prying up the bent leg with a very small flat-head screwdriver in the other. If you can successfully straighten the leg and remove almost all of the solder without lifting the pad, it should pull out without further drama.
I used soldering wick as well after desoldering, and it can be really tricky to save the original pcb
I have used tweezers while applying heat to the joint, then using my desolderin iron or a solder sucker to get the solder off of the pin, but that has given me mixed results. I then started using the nozzle to my desoldering iron to bend the pins up while it also applied heat, but to be honest, this could break things on the iron which isn't a good idea.
Really, there is no perfect technique. On the AEK I desoldered, the pins broke with tweezers but worked fine with the nozzle method. On a DC-2014, the nozzle method worked perfectly. On the Dell AT101 I restored, the nozzle was not very effective and broke pins, and tweezers turned out to be the best method for it.
Durability varies, I guess. Sometimes you get lucky, other times, ya wreck it.
The only Alps boards I've desoldered without ANY bent over pins were the NTC 6151N with blue alps and my Fame TH-5539 also with blue alps. Both boards also had an odd quirk of being MXAlps compatible, allowing either switch type to be used, though I think neither ever had an example of using MX switches.