DST setting in La Crosse Technology atomic clock

The clock has a confusing setting: "DST?  on/off".  Documentation does not explain it.

The setting directs the clock to follow or ignore the DST signal present in the WWVB radio broadcast. Even with DST "on", it sets to the correct non-DST time when it is standard (winter) time.  People in Arizona should choose "off"; everyone else should choose "on".  Unless you move to or from Arizona, you don't need to adjust the setting.

Until I did research, I did not know the WWVB radio broadcast included information about Daylight Saving Time.  Until I did research, I assumed incorrectly that the user has to manually toggle the DST setting on the clock twice a year, according to the political whims of Congress and local governments who choose the start and end dates of DST.

Canon PIXMA TR4520 (TR4500 series) support code 6000

LCD display says "support code 6000". inspired by https://youtu.be/EI63iQmJza4, i opened it up looking for a paper jam.

although i unscrewed every visible screw, only 4 were necessary to access the print head and carriage underneath the scanner bed (platen).  however, one screw is inside the U-turn of the scanner ADF (underneath the controls), which feels loose, like it can be opened, but it isn't obvious how.  how: there is a spring-loaded latch next to the scanner bed: use a narrow tool, e.g., screwdriver, to retract the latch, then the ADF U-turn will open, revealing one of screws to open the printer.  presumably the ADF U-turn is accessible to clear paper jams.

the spring-loaded latch can itself be removed and disassembled.  it's a little bit tricky to put the spring back to reassemble.

after opening, there are ribbon cables between the two parts.  i left those attached.

i moved the carriage back and forth and moved the gears but didn't see any obstructions or jammed paper bits.  reassembled the printer, and error message no longer occured.  happy to achieve victory, but disappointed not to be able to tell what was wrong.

the underside has parts that can be removed by unscrewing.  one of the parts is nontrivial to put back.  there is a wheel or gear with a notch, and things only fit if the gear is at the correct angle to accept a piece. there are two notches, each differently shaped.  i picked one randomly and it worked, and did not investigate fitting the piece into the other notch.

there is a small arm that extends when the gear is at the correct angle.

when the underside piece was not in the notch and printer reassembled, there was some error, but i did not record it.