Epson ET-8550 Error Code 100077 After DTF Conversion: Scanner Bar Binding, FFC Cable, and Scanner Motor Troubleshooting

Question

I converted my Epson EcoTank ET-8550 into a DTF printer, and now the printer gets stuck during startup. I have taken the printer apart, checked my work, reseated the scanner components, and verified that the FFC cables appear to be plugged in.

When I power on the printer, the scanner light comes on, but the scanner bar moves toward the left side and knocks against the side of the scanner assembly. The printer then displays error code 100077. I have already taken the scanner apart and reseated everything, but I cannot get past this error. What should I check?

Answer

From the video and symptoms you described, there are a couple of important clues.

The Scanner Light Coming On Is a Good Sign, but It Does Not Rule Out Every Cable Problem

The first thing I noticed is that the scanner illuminates when the printer starts.

This tells us that the scanner assembly is receiving at least some power and that part of the scanner's electrical connection is functioning. In other words, the scanner assembly is not completely disconnected.

However, I would not use the scanner light alone as proof that every scanner FFC cable is installed correctly. The scanner's sensing electronics, lamp, motor, and feedback system rely on different electrical circuits. It is therefore possible for the scanner to illuminate while there is still a problem with the motor connection, an FFC cable, a connector, or the scanner movement mechanism.

This distinction is especially important on an ET-8550 that has recently been disassembled for a DTF conversion.

The Biggest Problem I See Is the Scanner Bar's Physical Alignment

The second observation is much more significant.

From the video, the scanner bar does not appear to be sitting straight. It appears to be at an angle instead of running parallel to the wall or frame of the scanner assembly.

That is the first thing I would investigate.

The scanner carriage must travel smoothly along its guide. If one side of the scanner bar is ahead of the other side, if the carriage has come off its guide, or if the scanner mechanism was reassembled at an angle, the carriage can bind as soon as the motor attempts to move it.

If the scanner bar is visibly crooked, I would have difficulty imagining it traveling normally through its full range of motion.

This also fits very well with the knocking you are hearing on the left side.

What Does Epson Error Code 100077 Mean?

On the Epson ET-8550, error code 100077 is associated with an "FB BS+ Excess Load Error." In practical terms, the printer is commanding the flatbed scanner mechanism to move, but the scanner motor stops or the printer cannot confirm that the scanner is moving as expected. (BCH Technologies)

So, in simplified terms, the printer is essentially saying:

"I told the scanner to move, but it isn't moving the way it should."

There are several reasons this can happen.

1. The Scanner Carriage Is Physically Jammed or Misaligned

Based on your video, I would investigate this possibility before replacing electrical components.

With the printer completely powered off and unplugged, inspect how the scanner carriage sits on its track.

Look carefully at both ends of the scanner bar. The carriage should be properly seated and square with the scanner frame. It should not look twisted, tilted, or noticeably closer to one side of the scanner housing than the other.

If it was removed during the DTF conversion or scanner disassembly, one side may have been reinstalled incorrectly.

Do not force the carriage through the scanner. If something is mechanically out of position, forcing it can damage the belt, gears, scanner carriage, or motor.

2. Check the Scanner Drive Mechanism

The scanner motor does not simply push the scanner bar directly. There is a mechanical drive system transferring the motor's rotation into scanner carriage movement.

Inspect the scanner mechanism for things such as:

• A carriage that has come off its guide

• A belt that is not properly seated

• A loose or disengaged pulley

• A cracked or damaged gear

• A foreign object blocking scanner movement

• A wire or FFC cable entering the scanner carriage's travel path

• A scanner component that was reinstalled in the wrong position

Mechanical disengagement, damaged gears, and scanner movement resistance are among the conditions associated with error 100077. (BCH Technologies)

The fact that your scanner goes toward the left and then knocks against the side makes a mechanical alignment or movement problem particularly important to investigate.

3. Check the Scanner Motor Connection Separately From the Scanner Data Connection

You mentioned that all of your FFC cables are plugged in, which is good, but I would still inspect them very carefully.

An FFC cable can appear to be installed while still being:

• Slightly crooked inside the connector

• Inserted only partially

• Installed with the contacts facing the wrong direction

• Creased or damaged during disassembly

• Torn near the end of the cable

• Missing electrical contact on one or more conductors

• Installed into a connector whose locking tab is not completely secured

Also, remember that seeing the scanner light illuminate does not necessarily prove that the scanner motor circuit is connected correctly.

Pay special attention to the cable or connection associated with the scanner motor.

If the motor is not receiving the correct drive signal, the scanner can illuminate normally but still fail when the printer commands movement.

4. Inspect the FFC Connectors, Not Just the Cables

This is something people sometimes overlook after taking an ET-8550 apart.

Inspect the connector itself.

The small locking mechanism on an FFC connector is delicate. If the lock is damaged, lifted unevenly, or no longer applying pressure to the cable, the cable can look fully inserted while making unreliable electrical contact.

Also inspect the exposed conductive fingers at the end of the cable. If one is folded, scratched, contaminated, or damaged, reseating the same cable repeatedly will not necessarily correct the problem.

Be very careful when working around these connectors because damaging a connector on the main board can turn a relatively simple repair into a much more difficult board-level repair.

5. Pay Attention to the Knocking on the Left Side

The knocking sound is an especially useful diagnostic clue.

During startup, the printer expects the scanner carriage to perform a controlled movement. If the scanner is hitting the left side repeatedly, either the mechanism cannot move correctly or the printer is not receiving the expected movement feedback.

A scanner bar that is physically crooked can easily create this situation.

Therefore, I would not start by replacing the scanner motor just because the error references scanner movement.

I would first correct the obvious mechanical alignment issue.

Make sure the scanner bar is seated correctly and completely parallel with the scanner frame. Then inspect the belt, gears, guides, and anything else responsible for moving the scanner.

6. Scanner Encoder or Position Feedback Problems Are Also Possible

The printer needs feedback so that it knows whether the scanner has actually moved when commanded.

A scanner encoder or related feedback problem can therefore produce symptoms similar to a mechanical jam. If the scanner moves but the electronics cannot properly detect that movement, the printer may stop the startup process and report error 100077. Encoder contamination, misalignment, or failure is another documented possible cause of this error. (BCH Technologies)

That said, because your scanner bar visibly appears out of alignment, I would address the mechanical problem before spending much time troubleshooting the encoder.

Always start with the most obvious abnormal condition.

7. The Scanner Motor Itself Could Be Bad

If the scanner mechanism is properly aligned, the carriage moves freely, the drive components are correctly installed, and all cables and connectors have been verified, then the scanner motor becomes another possibility.

A motor does not necessarily have to be completely dead to be defective.

For example, it could attempt to move but lack enough torque to move the carriage correctly. The motor or its drive electronics could also work intermittently.

Error 100077 can be associated with scanner motor failure as well as mechanical, encoder, and connection problems. (BCH Technologies)

Again, though, I would not replace the motor until the crooked scanner carriage has been corrected.

8. A Main Board Problem Is Possible, but It Would Be Further Down My List

There is also the possibility of a main board failure affecting the scanner motor control circuit.

However, based on what I can see from your video, I would put that relatively low on the troubleshooting list.

You already have a visible mechanical abnormality: the scanner bar does not appear to be installed straight.

It makes more sense to investigate that condition first before assuming that an expensive electronic component has failed.

What I Would Check First on This ET-8550

If this printer were in front of me, I would approach it in roughly this order:

1. Power the printer off and unplug it.

2. Correct the scanner bar alignment. Make sure it is properly seated and parallel to the scanner frame.

3. Check whether anything physically blocks the scanner's travel.

4. Inspect the scanner belt, pulley, gears, and guide mechanism.

5. Check every scanner-related FFC cable again, paying particular attention to the scanner motor connection rather than assuming the illuminated scanner lamp confirms everything.

6. Inspect the FFC sockets and locking tabs for damage or incomplete engagement.

7. Check the scanner's encoder or movement-feedback components.

8. If everything above checks out, investigate the scanner motor.

9. Only after those possibilities have been eliminated would I give serious consideration to a main board problem.

The key observation in your case is that the scanner lamp is functioning, while the scanner bar itself looks visibly crooked and then knocks against the left side during startup. That points me first toward the scanner carriage installation and mechanical movement rather than immediately blaming the main board.

Addressing printer issues can be a complicated affair because so much of the diagnosis depends on physically inspecting, moving, measuring, and testing the components involved. For that reason, we're not able to provide remote troubleshooting, suggestions, or support for individual printer repairs. We do offer an in-person evaluation and repair service through our local BCH Technologies printer diagnostic and repair facility [https://bchtechnologies.com/printer-repair-service]. Because of high demand, repairs are handled on a first-come, first-served basis, and it may take a few weeks before we can schedule a printer for drop-off. Our services are structured so that we can repair either an entire printer or certain individual parts, with instructions available for how to proceed. We also recognize that our repair rates may not be the most economical option for everyone, so we strongly encourage self-help and online research when practical. A good starting point is YouTube and our BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. On our channel homepage, use the search icon located near "About" on the right side of the menu bar and search terms such as ET-8550 scanner, 100077, scanner motor, or scanner FFC cable. I receive dozens of questions every day asking whether I have a video covering a particular problem. After creating videos for more than nine years, it is difficult for me to remember every video we have published, so using YouTube's search function is usually the fastest way to locate the relevant material. YouTube may also recommend useful repair videos from other channels that address the same problem.

Thank you again for contacting BCH Technologies and for taking the time to provide a video and detailed description of what the printer is doing. Your support of our work and our YouTube channel is sincerely appreciated, and I hope the information above gives you a clearer direction for diagnosing the ET-8550's 100077 scanner error.