Difficulty

Easy

Steps

3

Time Required

                          30 minutes - 1 hour

Sections

1

  • How to Fix Continuous Jamming in Printer, Brother MFC-7840W
  • 3 steps

Flags

Member-Contributed Guide

An awesome member of our community made this guide. It is not managed by iFixit staff.

  • BackBrother MFC-7840W

  • Full Screen

  • Options

  • History

  • Save to Favorites

  • Download PDF

  • Edit

  • Translate

  • Get Shareable Link

  • Embed This Guide

  • Notify Me of Changes

  • Stop Notifications

What you need

Step 1

              How to Fix Continuous Jamming in Printer, Brother MFC-7840W
  • Remove the corner cover shown in image. Once the screws are out, some fiddling should get it loose.

Remove the corner cover shown in image. Once the screws are out, some fiddling should get it loose.

1024

Step 2

  • Remove the pictured screws and use a spudger to release the hooks highlighted in red.

Remove the pictured screws and use a spudger to release the hooks highlighted in red.

Step 3

  • The orange circled rocker is supposed to move once for every page spooled and momentarily press the button circled in red. When the lubricant between the gears mixes with dust it becomes sticky and the rocker does not behave as it should.
  • You will know this is the case when the printer jams only if you have more than one piece of paper in tray 1. Otherwise you will only have one piece of paper to feed and it will not jam.
  • Either clean the residue, add a new spring, or replace the old spring with a new and stronger one.
  • In my case I did not want to disassemble the printer further, and happened to have an old spring lying around from an old car stereo.

The orange circled rocker is supposed to move once for every page spooled and momentarily press the button circled in red. When the lubricant between the gears mixes with dust it becomes sticky and the rocker does not behave as it should.

You will know this is the case when the printer jams only if you have more than one piece of paper in tray 1. Otherwise you will only have one piece of paper to feed and it will not jam.

Either clean the residue, add a new spring, or replace the old spring with a new and stronger one.

In my case I did not want to disassemble the printer further, and happened to have an old spring lying around from an old car stereo.

To reassemble your device, follow these instructions in reverse order.

Cancel: I did not complete this guide.

                                                                                      6 other people completed this guide.

Author

                                      with 2 other contributors 


                    Kevin T

Member since: 11/18/2017

281 Reputation

                                      1 Guide authored                  



                       Badges:
                       6







                                                        +3 more badges

Stephen Leung - Feb 23, 2018

Reply

Thanks for writing this post. What is the size of the tension spring replacement I should look for? I don’t have any old stereos lying around to salvage from.

Kevin T - Feb 23, 2018

I’m not sure. You should probably look for something shorter than what’s in the printer. That way when you install it, it will always be in tentsion. Better shorter and stiffer, since you can always strech and cut later.

addison.pan - Jun 15, 2018

Reply

This fixed my problem. I bought the smallest spring diameter at orchard supply 1/8” diameter i think. but the springs were too long. so i cut it down. tried 4 or 5 lengths before i got it right.

If the tension is too strong, the solenoid won’t be strong enough to pull the arm down and you will get a “No Paper Error.” in that case you just need to slightly stretch out the spring and try again. Print without the cover and you will see if the solenoid is going up and down consistently.

The original spring has a really light tension so you need to hit that sweet spot.

Spencer - Sep 8, 2020

Can you help me out? I can’t get the side panel off.

matthias.dix - Jul 12, 2018

Reply

I just pulled the existing string a little further down and managed to get it back on the bottom hock. Worked like a charm for me…