The 5th and 8th (from the top) dots on my ImageWriter II (A9M0320) don't print. Things I've already checked/tried:
- Disassembled and cleaned the head. No change.
- Windings on the head all measure ~3 ohm resistance each.
- Each winding pin on the head measure around ~9 to ~11 volts when the printer is on.
- I wrote a small program on my modern PC to test each pin individually over serial (using the ESC G commands documented in the technical reference). I can hear each of the other pins actuating (striking?), but I hear nothing when either the 5th or 8th pins are being tested.
- Using my oscilloscope while the pins are being tested, I see waveforms on the good pins that basically match the drawings in the Sams ComputerFacts document. However, the 5th pin looks like it has no signal (just solid voltage level the whole time) during pin testing, and the 8th pin does have some kind of waveform but it's more square wave looking rather than the curved ramp up and down that the good pins have.
What should I do next? Should I try recapping the power supply? Should I look into replacing the ICs labeled HIC4 and HIC3 that seemingly drive pin 5 and 8 respectively?
