== CPC Plus Cartridges:LK1-LK6 - EPROM Address Lines ==
The six LKs are for A15,A17,A18 (address lines, of course, not the "A1-A18" pins).
VCC ---LK1--- EPROM.A18---LK2---CPC.A18
VCC ---LK3--- EPROM.A17---LK4---CPC.A17
VCC ---LK5--- EPROM.A15---LK6---CPC.A15
Some cartridge PCBs don't have any LKs installed, instead, the etched circuit has hardwired connections between some of them. One could scratch them off, and then use the LK soldering points to reconfigure the board for eproms of other size.