The print of Panasonic FP-7835 is very dark. What is the darkness control code of Panasonic FP-7835 Photocopier

It needs cleaning inside and you need a new toner cartridge. Use genuine Canon Toner cartridges and never ever, have them refilled. What you are seeing is the end result. The developer roller is only made for a certain life span and is part of the toner cartridge.

i would suggest changing out the developer...if it becomes overtoned it will get a dark background

Laser unit. You can try re seating the connectors on the laser unit.

E1-22 indicates a problem with the Polygon Motor Sychronization....this is a problem in the laser unit either the Driver pcb is shorted or broken, the Laser unit pcb is defective, the laser unit itself could be defective.

you meset klin optical glass and mirror

it could be the developer dropping toner or the cleaning section clogged up. i would recommend a technician.

dark copies you mean there is a dark background but image is still there?
it is usually happens when all mirrors and **** glass becomes dirty. you should clean it
well if you mean an image with pure black copy output, probably your exposure lamp is busted or the thermostat is open. :)

My Sharp is a different model but my reset is:
Hit:
Clear (then)
Auto (then)
Clear (then)
Auto (then)
14 THEN
Start
It resets itself.

You can find the parts on the web... Look in Precision Roller.com. They have the parts you want.....

Have you tried a new GENUINE Panasonic Toner Cartridge?