Excellent inputs from Chris.
One thing I would do with the oscilloscope is set it for a single-sweep, positive-edge trigger, with a time scale per-division around 5 milliseconds.? This is a slow trace to capture what the power rails look like when a) you plug in the power cord (Vin only), and b) when you press the power-on button (12V V+, VCC and VDD).? I am curious whether the voltage goes up and holds a value for many milliseconds before going down, or whether it never gets very high, or whether it does go to a normal value but immediately changes.? Such info would help direct troubleshooting.? If 12V holds at a high value for many milliseconds, I would decrease the scan rate until I could see it go down, and what that looked like.? If instead it looks like it doesn't go up high at all, I would increase the scan rate to see if it would catch any much shorter event right after the rail starts going up.? Anyway, that's the general idea, and the data you see could inform where to look next, when used along with the current draw you can measure in the various states.
Stan KC7XE
