Sharp Compact Copier Model #Z-77. When I try to copy the letter L comes up and nothing copies.

Enter code(# interrupt c interrupt 14 and copy key)

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02.LSU trouble
03.shading trouble (black correction
04. shading trouble(white correction)
05. shading trouble
06.Abnormal laser output

Duplex unite only use a4 size not other size.You can try other size before configure.

Install the developer unit and toner cartridge properly and close the copier side covers well ie the front and the right covers.

It probably the toner cartrisge is empty or if there's an error code H4, the heater lamp is spoiled

the paper is set to 8.5-11 and you are running letter r paper u must set the copier tray to the proper size

"L" and what number? 1?
The scan head is locked. Unlock it

Manual is here:
http://www.sharpusa.com/files/cop_man_AL1641CS_1631.pdf

Not familiar with that model but what I would try is to turn off the copier remove the glass and try moving it by hand, then turn it on and see what happens it may have a bad motor

Try using heavier paper say 80gsm. Or adjust light exposure if possible.

1-check and make sure the paper sizes coreresponds : If using Letter it must indicate 8 1/2x 11 or (Letter) not Legal or 8 1/2 x 14.

2- the tires are slipping and trowing the timing off. change tires (cheap)