I unplugged everything from the main board of my Canon Pixma MX340 multi-function inkjet so I could take a look at components on that circuit board. This examination was the originally planned end point for my teardown. Now I'm looking over what I have on hand to see where to go from here.

The first thing I did was to plug everything back into the main board. This turned out to be a lot easier than I had originally expected, because (aside from two exceptions) every connector was distinct from another so it was easy to make sure I didn't plug something into the wrong place. I believe this was another sign of intentional design for serviceability.

Once everything was plugged in, I had the disembodied nervous system of a Canon Pixma MX340 separated from almost every mechanical component. I plugged in a power cord and it turned on and started running its power-on self-test sequence. Nice!

I kept the two encoder-equipped DC motor assemblies intact enough to run through their respective self tests, so the paper feed motor could run through its sequence and the print carriage motor could do the same.

There were a total of four optical interrupter sensors. Two in the automatic document feeder and two in the paper feed mechanism. They were all designed so the "normal" position blocks the beam and the power-on self-test sequence doesn't do anything requiring those beams to be unblocked. So even though these sensors have been separated from their respective mechanisms, all I had to do was to stick something opaque into these sensors to fool the computer.

Beyond that, though, fooling the computer got more complex. The scanner tries to run through its homing sequence. It would fail because the sensor bar has been separated from the homing marker and I don't see an easy way to fool the system. I guess I could set up a short rail so its motor can move the marker into view and out of view, but that's more effort than I care to expend on such a project.

And finally, the computer complains it can't talk to the absent ink cartridges. I expect that communication to be protected in multiple different ways in the interest of protecting their revenue stream, so I'm not even going to try to figure out how to spoof it.

Since this disembodied MX340 nervous system still runs, I'm inclined to keep the electronics together as I dispose of the rest. But before that, they get to hang out together one last time for a big group photo.

This teardown ran far longer than I originally thought it would. Click here to rewind back to where this adventure started.