It is a blueprint. A people can understand how the product has made. It show all of significant components, parts, or tasks (and their interconnections) of a PCB board, device, flow, process, or project by means of standard symbols. Schematic diagrams for a project may also be used for preparing preliminary cost estimates. Using schematic diagram PCB repairing is easier. A technician can understand easily how the circuit is working.
I have uploaded here the circuit diagram its for Brother sewing machine. Basically Brother KE340C, B438E, ZE850 etc. Main pcb’s are almost same. A little difference may you see.
So, I think All kind old model’s of brother PCB will be very essay to you. Please enjoy, If you face any difficulties or any problem don’t feel hesitation to share with us.