I've just replied to your other post but I agree with nophead here, I'm not sure if a new board would solve the issue.
If you did want to get a new board anyway, there's a great blog post here documenting the upgrade process from another Mendel90 user [
janoc.rd-h.com]
I'm currently considering switching to an SKR board with some TMC drivers to try to reduce the noise of my printer a little and upgrade to Marlin 2.0. I'd also like an LCD and a Z probe but I can't achieve this on the Melzi because I have the original Atmega 644P, which has very little space for additional features.
I don't think I need all the features of the SKR pro so I'm looking at the SKR 1.4 turbo, which can be had for as little as ~£20 from banggood. I also don't think it's worth getting the TMC2130 like in the blog post, the TMC2208 should be fine.