The knob on my e7D started behaving badly, especially when zooming in and out. I had another e7D with a dead screen, but a smooth-working knob. So I took them both apart and swapped the good knob to the one with the good screen. This documents that process. (Sorry that the alignment of the pictures is not good - that happened when I printed it to PDF from my blog page. If you want to view the original, go to:
http://smartini.life/2018/11/07/disassemble-raymarine-e7d-chart-plotter-mfd/)
http://smartini.life/2018/11/07/disassemble-raymarine-e7d-chart-plotter-mfd/)