Canon MF5750 Printing Wavy Zigzag Text and Double-Line Images: Causes, Error Symptoms, and Fixes

Question

My Canon MF5750 isn't printing consistently. In the middle of three lines, about 10 characters look doubled-like each character is printed twice with roughly a 0.5 mm offset-then the next three lines print normally. It feels like there might be a small bump on a roller/cylinder causing the shift. What could be causing this, and how do I fix it?

Answer

Based on your description-only certain characters in the middle of a few lines look "double-printed" with a tiny offset (about 0.5 mm), and then the printing returns to normal-this is a classic symptom of a position-tracking/registration issue rather than a toner cartridge problem. It often feels like a "bump on a cylinder," but many times the "bump" is actually dirt or smearing on a position reference strip/belt or a momentary slip in paper/carriage tracking.

What's most likely happening

1) Dirty encoder strip / timing strip (most common for "double characters")

Your symptom matches what we usually see when the printer momentarily misreads position and "thinks" it's printing in the right place when it's slightly off-so it lays down a second, offset impression of the same characters.

• On many printers, the position system uses a clear encoder strip (sometimes called a timing strip or encoder scale) with very fine markings.

• If that strip has toner dust, ink-like residue, fingerprints, or haze, the sensor can misread for a brief moment-resulting in wavy/zigzag text, double-line edges, or duplicated characters that only happen intermittently (often in a repeating pattern along the page).

Fix: Carefully clean the encoder strip.

• Power off and unplug the printer.

• Open the printer so you can see behind/around the carriage path area (or where the sensor reads the strip).

• Look for a thin transparent strip stretched horizontally across the printer's travel path.

• Use a lint-free cloth lightly dampened with distilled water or 90%+ isopropyl alcohol.

• Wipe gently along the strip, supporting it with your finger behind the cloth to avoid tugging it out of place.

• Avoid using paper towels (they shed fibers), and do not scratch the strip.

Important: Don't yank or twist the strip-if it comes out of its slots, it can create bigger alignment problems.

Even though your unit is a laser model, the symptom you described is still consistent with an encoder/timing reference contamination issue-people often describe it exactly the way you did: "like a bump on a cylinder," because the defect seems to come and go in bands.

2) Contamination on a drive/transfer surface (secondary possibility)

If your printer has a belt/roller that the paper passes across, a small piece of stuck debris, adhesive residue, or toner clump can cause brief slippage or vibration. That can mimic double-printing in short sections.

What to check:

• Any roller you can safely inspect (feed roller area, output rollers).

• Any area where toner dust could cake up.

• Paper path: look for labels, tape residue, or torn paper fragments.

Fix: Gently remove visible debris and clean rollers with a lint-free cloth and a small amount of water (or rubber roller cleaner if you use one). Don't soak anything.

3) Paper/feed slippage or moisture issues

If the paper is slightly damp, very smooth, or inconsistent thickness, the printer can momentarily micro-slip during imaging/transport, which can produce a repeated edge or doubled text.

Fix:

• Try a fresh ream of paper stored in a dry place.

• Test different paper (standard copier paper, 20 lb / 75 gsm).

• Fan the stack and confirm guides aren't too tight.

About error codes

You didn't mention any error codes on the MF5750 display (for example, E-codes or paper/toner warnings). That's actually common with this type of issue: registration/encoder contamination problems often do not trigger an error code-the printer "thinks" it's operating normally, but the position reading is slightly off for a moment.

If your printer does show an error code (even occasionally), include it next time and I can explain what that specific code typically points to.

Addressing printer issues can be a complicated affair due to the hands-on nature of the problems, and the condition of parts in front of you matters a lot. So, we're not able to provide remote troubleshooting, suggestions, or support for printer repairs. We do offer an in-person evaluation and repair service through our local diagnostic facility (printer repair service https://bchtechnologies.com/printer-repair-service). Given the high demand, we operate on a first-come, first-served basis, and it may take a few weeks before we can schedule your printer for drop-off. Our services are structured to repair either a whole printer or specific parts, with clear instructions on how to proceed. However, we acknowledge that our rates aren't the most economical, so we strongly recommend self-help through online research first. A great starting point is YouTube, especially our BCH Technologies homepage (BCH Technologies YouTube channel https://youtube.com/@bchtechnologies). To find the most relevant videos quickly, use the search icon next to "About" on the right-hand side of the menu bar. I receive dozens of questions every day asking if we have a video for a specific issue. After creating videos over the past nine years, it's tough to remember every single topic offhand-so YouTube's search tool is the fastest approach. YouTube may also recommend helpful videos from other channels that can assist you as well.

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