Hey there. I’m just starting my DIY journey on a pair of KSC75 with the MMCX mod. As I’m trying to tin the wires I notice that the solder can stick to the positive but can’t stick to the ground wire. As a result I can’t solder the ground wire to the MMCX socket. Any advice?
Make sure there is no coating left on the wire (hold in blue part of a lighter flame or gas torch, or scrape off with sharp box cutter). Make sure the surface is clean (rubbing alcohol, etc.) and use flux of some sort.
Thanks! So I notice the positive wire has coating which I’ve removed and it works fine. But the ground wire doesn’t seem to have coating but the actual copper wire is intertwined with some white fabric materials I believe - could that be the cause?
May I also ask if you’ve done the KSC75 yourself?
Anyway, more items for my shopping list now 
No, just general soldering experience 
Gotcha, I’m sure it applies. Asking because if you did what I have said might make a bit more sense. I’m sure I am not the only one that encounter this before but most have more experience than I do.
I only have some rubbing alcohol and a knife so I’m gonna give that a go now. Many thanks again!