Epson EcoTank ET-5800 Printing Large Black Squares in the Same Spots: Causes, Diagnostics, and Fixes

Question: My Epson ET-5800 keeps printing big black squares repeatedly in the same areas, but it also prints normally in the background. What causes this, and what parts or steps should I check?

Answer: 

Now, let's dig into what you're seeing: when an Epson ET-5800 prints large black squares in the exact same pareas repeatedly, while the rest of the page still looks mostly normal, that usually points to a logic/command-side problem (timing, data, or firing control) rather than a simple ink flow issue. In other words, the printer is often "firing" nozzles at consistent intervals due to a signal/control fault-so the defects show up as blocks in consistent locations.

Below are the most likely causes and the best order to test them.

1) Rule out software/data corruption first (fastest, no parts needed)

Before opening the printer, confirm whether the squares are coming from the computer/driver pipeline or from hardware.

Do these quick checks:

• Print a built-in printer report (like a nozzle check or status sheet) directly from the printer's control panel.

• Print the same document from:

  • A different application (PDF viewer vs. Word, etc.)

  • A different computer

  • A different connection type (if possible: Ethernet vs. Wi-Fi)

• If available, try printing from a phone using Epson's app, or print a simple image file stored locally.

What the results mean:

• Squares appear on internal printer reports too: strongly indicates hardware (carriage timing, mainboard, cables, encoder).

• Squares only appear from one computer/app: likely driver, print settings, or corrupted print spool data.

Software fixes worth trying:

• Remove and reinstall the Epson driver (avoid using a "generic" driver if possible).

• Clear the print queue/spooler and reboot the computer.

• Temporarily switch driver modes (if available) such as "Standard" vs "High Quality," or turn off special features like "High Speed," "Edge Smoothing," etc., just to see if behavior changes.

• Try printing with "Black Only / Grayscale" vs "Color" to observe whether the blocks are strictly tied to K (black).

2) If the squares repeat in the exact same physical locations: suspect timing/control (encoder or carriage signal)

When defects land in the same spots on the page every time, the printer is typically firing at incorrect, repeatable timing intervals. Two common reasons:

A) Encoder strip contamination or damage (CR timing issue)

The encoder strip is the thin clear strip behind the carriage that the printer uses to track position. If it's smeared with ink, scratched, or partially detached, the carriage position feedback becomes unreliable, and firing can happen at the wrong moments-creating repeated marks in consistent places.

What to check:

• Open the printer and locate the encoder strip behind the carriage path.

• Look for ink mist, fingerprints, smears, haze, scratches, or tears.

• If it looks dirty, clean it gently with a lint-free cloth lightly dampened with distilled water or isopropyl alcohol (very lightly). Avoid pulling it out of alignment.

Symptoms that fit encoder issues:

• Repeating artifacts that are position-related

• Sudden onset after an ink spill, paper jam, or heavy use

B) Carriage board/contact contamination (repeated firing in blocks)

Sometimes the carriage contacts or the small board on the carriage gets contamination or oxidation. That can create noisy signals and "false firing" that can appear as blocks or bands.

What to check:

• Power off and unplug the printer.

• Inspect the carriage area for ink buildup or moisture.

• Inspect and reseat the connectors you can access safely (without forcing anything).

3) Inspect and reseat the printhead ribbon cables (very common cause of strange repeated artifacts)

A loose, partially seated, or slightly damaged printhead ribbon cable can cause repeated data corruption-sometimes presenting as solid blocks, missing patterns, or repeating shapes.

Steps (high level):

• Unplug the printer.

• Access the carriage connections (this varies by model).

• Carefully reseat the ribbon cables (do not crease or fold them sharply).

• Look for:

  • Burn marks

  • Cracks

  • Torn edges

  • Ink contamination on contacts

Important note: Ribbon cable damage isn't always obvious; even minor cracking at the bend points can cause repeatable print artifacts.

4) Consider mainboard/logic board failure (especially if it happens across all sources)

If the squares:

• appear on nozzle checks or internal reports, and

• stay in the same locations regardless of file/computer/connection,

...then the failure is often on the printer's logic side-commonly the mainboard (or data path circuitry) mis-driving head firing timing.

Why this happens:
The mainboard controls firing sequences and timing. If parts of that circuit are failing, the head can be told to fire repeatedly at fixed intervals-creating the same blocks in consistent locations even while other content prints "normally in the background."

Parts commonly associated with this symptom:

• Mainboard / logic board

• Carriage PCB / head driver path (depending on model architecture)

• Head data cables (if they test bad)

5) Less common but possible: printhead electrical damage (not just clogging)

Most EcoTank print issues are clog/air-related, but large repeating black squares are usually not caused by simple clogs. Still, if the printhead has an electrical failure (shorted nozzle group or internal damage), it can output abnormal patterns.

Clues it might be the head:

• The black squares correlate strongly with black-only printing

• Head cables look good, encoder is clean, and software sources are ruled out

• You see severe abnormal patterns on nozzle checks that don't change with cleaning cycles

Practical diagnostic "decision tree" (quick way to narrow it down)

• Squares show on internal nozzle check/status report → hardware path

  • Clean/check encoder strip → reseat/inspect head ribbons → then suspect mainboard

• Squares only show from one computer/app → software path

  • Reinstall driver → clear spooler → try different connection/app/file type

• Squares always in the same spots regardless of file → timing/control issue

  • Encoder/CR timing or logic board most likely

Addressing printer issues can be complicated because they're so hands-on by nature. Because of that, we're not able to provide remote troubleshooting, step-by-step repair coaching, or hands-on support for printer repairs. We do offer an in-person evaluation and repair service through our local diagnostic facility: BCH Technologies printer repair service (https://bchtechnologies.com/printer-repair-service). Due to high demand, we run on a first-come, first-served basis, and it may take a few weeks before we're able to schedule a drop-off. Our services are structured to repair either a complete printer or targeted components, with clear instructions on how to proceed. We'll also be upfront that our rates aren't the most economical-so we strongly recommend self-help through online research first. You can start on YouTube or by visiting our channel homepage: BCH Technologies YouTube channel (https://youtube.com/@bchtechnologies). Use the search icon next to "About" on the right-hand side of the menu bar to find specific topics. I receive dozens of questions daily asking if we have a video for a specific issue, and after creating videos for the past nine years, it's tough to remember every single one on demand-so YouTube search is the fastest route. YouTube may also suggest helpful videos from other channels that match your exact symptoms.

Thank you again for reaching out and for supporting what we do. I truly appreciate your patience, and I hope these checks help you pinpoint whether this is a driver/data issue or a carriage/logic-side failure so you can decide the next best step.