The 6A00 is a Canon generic code for paper path jam. Some where in the paper path a sensor is activated indicating paper jam so the printer will give off a 6A00 code. As a Canon tech, I usually find the code, almost 90% of the time, is related to the purge unit being jammed with something and not being able to move. Moving the print head assembly will not clear a purge unit if its jammed with paper, paper clips, push pins, screws, cookie crisp, flower bud pods or the like. And yes I have found all those things in a purge unit. The offending item needs to be removed or the purge unit needs replacement. A Pixma MP830 would still be under Canon warranty, get it into a shop and save yourself the hassel.
Incidently, the 6A00 error pertains to all Canon printers made in the last several years, its not just used in one model. And its always a paper path error or purge unit.
I forget myself so here goes, the purge unit, called a spittoon assembly in an HP, lexmark, and other inkjet printers, is where the print head assembly parks when not in use, also its other job is to clean and make sure the print head is clean and open for printing. That is why you'll find the print head assembly parked on top of it. It also has a an electrical pump to milk the print heads and test for ink flow.
Error 6A00 on Canon PIXMA MP800
