The traces coming from the ZX Spectrum keyboard membrane are prone to breaking. If parts of your keyboard have stopped working you'll need to replace the membrane.

In this video I'll show you how.

Replacement parts
Retroleum - https://www.retroleum.co.uk/
ZX Renew - https://zxrenew.co.uk/

0:00 Introduction
0:24 Disassembly
1:50 Changing the membrane
2:57 Fitting the ribbon cable clamps
4:50 Finished