Well I repaired my mechanical keyboard I bought from OCUK probably about a decade ago :O
It's a QPAD one with old skool 2 legged round LED diodes in each Cherry MX brown switch. I managed to get some of the dodgey switches fixed - which were ghost typing sometimes - by just dribbling some IPA down inside them, and operating the switch several times until it dried out.
As for the LEDs, a couple had burnt out so I wanted to replace them. I had the idea of using some of the same coloured LEDs from the scroll lock, num lock and caps lock so they would be the exact correct colour and spec, and then replace the num/caps/scroll with new colours to something funky. So here's how it went...
I managed to hold my soldering iron over the two legs of each of the old blue LEDs to get them out ok. Same with the ones over the num/caps/scroll, but these ones were offset on stand offs a bit different. No drama though.
I replaced the blue ones that were bad with the now spare ones and they worked and when set to the 4 different brightness levels, they were generally pretty good and in line with all the others, if anything a tiny bit brighter, but barely noticeable. Cool.
Then I went to replace the num/scroll/caps leds and faced some issues. First of all I bought two different types, green and pinky/purple. I did this because they operated at different voltages and I was not sure what spec to get. Off the top of my head it was something like 2.5 to 3v. Anyway, the green ones would not dim on the lower settings at all, but the pink ones did fine. So I thought I would use the pink ones.
Unfortunately when I did the through hole soldering on these ones, I just could not get the solder to flow into hole and make a good connection, despite best efforts, multiple techniques and a load of flux. In the end, I think I end up just scorching the PCB and damaging the traces inside the hole perhaps. I gave up. The num/scroll/caps all still function, just no LEDs now. My soldering skills are very limited. I have a very basic iron. Oh well.