Brother MFC 7420 scanner is locked, how to unlock it?

SOURCE: Refill toner Brother MFC 7420

open front cover, press OPTION button, on the LCD will appear a message "NEW DRUM?" ....DO NOT RESPOND....just type on the keyboard "*00" and there will appear a message "Accepted" and use it in your pleasure.

PS. in any case i blocked with paper labels the viewing windows from transparent plastic on the toner itself....

Mr. Brother, do not try to be smarter than your customer

SOURCE: I can't find the back door sensor on Brother MFC-7420

I have the answer. I just fixed mine. The sensor is not really on the door. You have to remove the door by openning it all the way and carefully sliding it out ( one of the pegs holding the door is hourglass shaped. This will slide out first. The other is round. You will see a black flap that covers a red drum. Pull the flap down carefully. There will be a six inch long rod it's about 1/8 of an inch in diameter. It extends from the middle of the flap all the way to the right side. This probably popped out of place. Make sure that it is all the way to the right as this is where the sensor is. There is a little spring on the bar on the left side. This should be straight up and down. if it is not, then you need to fiddle with the bar.
The trick was that the sensor is NOT on the door, but on this inner flap. When the door closes it pushes this flap agains the drum and the little bar activates the sensor.
Please do not applaud so loud, you are ambarrazing me!!! hehehe. Good luck!.

SOURCE: error 2001 on brother mfc 7420

please tell me more! i just checked my brother manual and i do not see a error code 2001????????????

SOURCE: mfc-7420 Black Line horizontal across paper in 3 places

try moving the small blue slider on top of the drum cartridge side to side 10 times.

SOURCE: Black lines in copies and fax's Brother MFC 7420

If the black lines comes when using the ADF (top feeder), try to see if you get the same problem when using the scanner glass or receiving faxes. If you don't, you simply have to clean the glass strip to the left of the a4 sized scanner glass. Wipe it with a dry cloth piece, no paper and no water/alcohol. If you see some dirt there that you're unable to simply wipe off, try to use a cotton wool to "rub" it off.