How to Fix Epson ET-8550 Error Code 100077: Scanner Motor and Encoder Solutions

Question :

I’m getting an error code 100077 on my Epson ET-8550 printer. Do you know how to fix this?

Answer:

Understanding Epson Error Code 100077 on the ET-8550

Error 100077, also known as "FB BS+ Excess Load Error", occurs when the printer detects that the scanner motor has stopped running unexpectedly during operation. Essentially, the printer believes something is physically or electrically blocking the scanner head’s movement.

This error can be triggered by a variety of mechanical, electrical, or sensor-related issues. Let’s walk through each possibility.

1. Mechanical Disengagement

One common cause is mechanical misalignment or component disengagement:

• The scanner carriage rail may have popped out of place.

• The scanner motor pulley could be loose or stripped.

• Internal drive gears within the scanner assembly may be worn or broken.

These issues can physically block or restrict the scanner from moving freely, triggering the excess load error.

2. Encoder Sensor Problems

The encoder sensor tells the printer how far and how fast the scanner is moving. If the encoder strip is:

• Contaminated with grease or dust,

• Misaligned,

• Worn out,

…it may send incorrect signals, causing the printer to think the scanner is stuck—even if it’s not.

3. Flat Flexible Cable (FFC) Issues

The scanner’s data and power are transmitted through a thin Flat Flexible Cable (FFC). If this cable is:

• Damaged,

• Unseated,

• Misaligned,

• Or pulled from the mainboard incorrectly,

the printer can lose communication with the scanner motor.

⚠️ Caution: Many users damage the socket on the mainboard when attempting repairs. This connection is delicate, and once the socket is compromised, it becomes extremely difficult to repair without replacing the entire board.

If you're looking for a replacement cable, we carry all three FFC cables used in the ET-8550 scanner:
➡️ ET-8550 Scanner Cables – BCH Technologies
(https://bchtechnologies.com/search?type=product&collection=all&q=et-8550+scanner)

4. Component-Level Failures

If the mechanical and cable systems seem fine, the problem may lie deeper:

• The scanner motor itself could be burnt out.

• The encoder sensor might be failing intermittently.

• The mainboard (logic board) may have a failure that prevents it from properly powering or controlling the scanner motor.

This kind of failure usually requires parts replacement and advanced diagnostics.

If You’re Considering a Repair

Diagnosing this type of issue can be very hands-on and may require disassembly, cable inspections, and sensor cleaning. If you’re confident working on hardware repairs, start with the scanner cable connections and check for any physical obstructions. If you’re not sure, we recommend seeking professional assistance.

A Note on Support and Service Options

Printer repair can often involve intricate, hands-on work, and because of this, we are unable to provide remote troubleshooting or technical support. However, we do offer a comprehensive in-person evaluation and repair service through our printer diagnostic facility (https://bchtechnologies.com/printer-repair-service). Please note that due to high demand, service is offered on a first-come, first-served basis, and there may be a wait time of a few weeks before we can take in your unit.

If you're more inclined to DIY, we highly encourage using online resources. Start by exploring our YouTube channel (https://youtube.com/@bchtechnologies). Use the search icon next to the “About” tab to find detailed videos by keyword. We’ve produced hundreds of videos over the years, and searching specific terms is the fastest way to find what you need—sometimes even from other helpful channels YouTube might recommend.

Thanks again for your trust in BCH Technologies, and we hope this helps you get your Epson ET-8550 back up and running!