Heathkit manuals included extensive chapters on how the 6808 microprocessor (a cousin to the 6800) addressed memory, how the PWM motor control worked, and how the ultrasonic ping sonar calculated distance. This section is pure gold for modern restorers.
Learning to use the top-mounted keypad to talk to the Motorola 6808 CPU. Heathkit Hero 1 Manual
Physical copies often appear on eBay, frequently fetching high prices from collectors who want the original "blue-spine" binders. Heathkit manuals included extensive chapters on how the