Servo testing woes

A project log for 6502sbc Robot

65C02-based SBC with a discreet-part servo controller and ADC intended as a intermediate-skill learning tool.

CarbonCarbon 08/01/2014 at 18:150 Comments

The servo control board works...sort of. I can alter the state of the status LED quite easily and drive a servo motor, but they quickly lose functionally. About a minute after power-on any attached servo start acting erraticly and becomes unresponsive. A check with a logic analyser shows that the 74HC74 (dual D-type flip-flop) I'm using as a clock divider works initially but quickly looses it's mind and starts spewing what looks like random noise. Adding extra caps and swapping out the part doesn't seem to help. I'm beginning to suspect I may have missed a critical design detail somewhere. I'd love to have an o-scope to see more detail of what's going on - might actually buy one just for this project.