How to Fix Continuous Jamming in Printer, Brother MFC-7840W
Kevin T and 2 other contributors
Last updated on Aug 9, 2019
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2 comments on steps, 27 guide comments.
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Community-Contributed Guide
An awesome member of our community made this guide. It was not created by iFixit staff.
What you need
Tools
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Spudger4.9
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Remove the corner cover shown in image. Once the screws are out, some fiddling should get it loose.
Ask FixBot
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Remove the pictured screws and use a spudger to release the hooks highlighted in red.
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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.
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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.
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Either clean the residue, add a new spring, or replace the old spring with a new and stronger one.
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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.
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To reassemble your device, follow these instructions in reverse order.
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27 Guide Comments
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.
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.
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…
