Epson ET-8550 DTF Conversion False Paper Jam: Diagnosing Carriage Knocking, Capping Station Interference, and Sensor Errors

Question

I recently purchased and converted a second Epson EcoTank ET-8550 for DTF printing. The printer produces good-quality prints when it works, but it frequently stops at the beginning or middle of a print and reports a paper jam even though no paper or film is physically jammed.

I have tried changing the printer's paper type and thickness settings, matching the settings in CadLink, selecting 11-by-17-inch paper, using different print-quality settings, and turning the paper-mismatch option on and off. I have also cleaned the capping station, cleaned beneath the printhead using a shoeshine-style method, and carefully cleaned the surrounding areas. None of these steps has resolved the problem.

I have noticed a slight knocking sound when the printhead carriage moves toward the right side near the capping station. Whenever I hear that same knocking sound, the printer soon reports a paper jam. What could be causing this, and how should I diagnose it?

Answer

The Knocking Sound Is an Important Diagnostic Clue

The repeated knocking near the right side of the printer is probably the most valuable detail in your description. Because the sound occurs immediately before the paper-jam message, I would first investigate a physical obstruction affecting the printhead carriage, commonly abbreviated as the CR.

The printer may display a paper-jam message even when no sheet of paper is trapped inside. Epson printers monitor several mechanical movements and sensor signals during printing. If the carriage cannot travel to its expected position, or if the printer does not receive the expected sensor response within a certain period, the firmware may stop the print and report a paper jam.

No specific numerical error code was included in your question, so the reported condition is a general paper-jam error rather than a confirmed numbered Epson service code. If the printer later displays a code such as a six-digit fatal error, record the complete code because it may identify the affected mechanism more precisely.

Check Where the Carriage Stops

Observe the carriage position at the exact moment the error occurs. Do not place your hands inside the printer while the carriage is moving. After the error appears, turn off and unplug the printer before inspecting or manually moving any components.

If the carriage consistently stops or knocks when approaching the right-side parking area, examine the following areas:

• The capping station platform

• The rubber printhead cap

• The wiper blade

• The flushing or ink-collection pad

• The capping-station springs and lifting mechanism

• The transmission slider and change-gear assembly

• DTF ink tubing, dampers, brackets, and drag-chain components

• Any FFC cable, wire, or ink tube that may be entering the carriage path

The printhead carriage must be able to move smoothly over the service station and enter its home position without striking the cap, wiper, frame, or conversion components.

Do not continue running repeated print tests if the carriage is physically hitting something. Repeated impacts can damage the printhead surface, carriage frame, CR belt, capping-station mechanism, encoder strip, or printhead cables.

Capping Station and Change-Gear Problems

The capping station does not remain at one fixed height. Its mechanism raises the cap when the printhead is parked for sealing, cleaning, and ink extraction. It must then lower sufficiently before the carriage moves away from or across the service-station area.

This movement is controlled through the printer's gear train, including the change gear and transmission slider. If the mechanism is contaminated, incorrectly timed, partially disconnected, or unable to complete its movement, the capping station may remain slightly too high. The printhead or carriage can then strike the raised cap, wiper, or service-station platform.

That impact may create the knocking sound you described. After the carriage fails to reach its expected position, the printer can stop and report a paper-jam condition.

Inspect whether the capping station lowers completely and evenly. Possible causes include:

• Dried DTF ink restricting the service-station movement

• A spring that is disconnected, stretched, or installed incorrectly

• A gear that is damaged or not fully engaged

• A transmission slider that is binding

• A wiper blade that does not retract

• A capping-station platform that was reassembled out of position

• A flushing pad or rubber cap that has lifted from its holder

• A foreign object underneath or beside the service station

Cleaning the top of the capping station does not necessarily correct a timing or gear problem underneath it. The visible cap may look clean while the lifting mechanism below it remains jammed or incorrectly positioned.

For a clearer view of the printer's internal structure, search for SKU REF-ET8550-Parts on the BCH Technologies website [https://bchtechnologies.com]. The ET-8550 Exploded Parts Diagram - Repair Reference Guide, Annotated Edition provides an organized diagram of the printer's internal assemblies.

On Page 4, near the upper-left portion of the diagram, locate Gear No. 549, the transmission slider. Selecting that component should lead to a more detailed product page explaining how the mechanism operates. Many components in the guide link directly to their corresponding product pages, and YouTube icons identify parts for which repair or installation videos are available. The guide is updated as additional parts, technical information, and videos become available.

Inspect the DTF Conversion Components

Because this problem began after conversion, also check everything that was added, moved, or rerouted during the conversion.

A DTF ink tube can look properly installed while the carriage is near the center but become tight when the carriage reaches the right or left end of its travel. The same problem can occur with a drag chain, cable bundle, damper assembly, printhead cover, or bracket.

Move the carriage gently by hand only after disconnecting power. Watch the tubing and cables throughout the entire carriage path. The tubing should not:

• Pull the carriage backward

• Become tight near the capping station

• Catch on the scanner frame or printer housing

• Fold under the carriage

• Press against the encoder strip

• Push a damper, fitting, or printhead cover downward

• Interfere with the capping-station wiper or platform

Also check whether the installed dampers, adapters, or printhead cover sit too low. A component attached to the carriage may be contacting the capping station even when the original Epson carriage would have cleared it.

A rhythmic knock near the right side often indicates that the motor is attempting to move the carriage into position while something is preventing the carriage or service station from completing the movement.

Check the Encoder Strip and CR Drive System

The transparent CR encoder strip behind the carriage allows the printer to track the carriage's horizontal position. If the strip is contaminated with ink, installed outside the carriage sensor slot, twisted, scratched, or incorrectly tensioned, the printer can lose track of the carriage position.

Inspect the encoder strip for ink mist, fingerprints, dried cleaning solution, or physical damage. Clean it only with a suitable lint-free material and minimal moisture. Do not pull, crease, or aggressively scrub it.

Also inspect the CR belt and pulley system. The belt should remain properly seated and tensioned. A slipping belt, obstructed pulley, or incorrectly installed carriage component may produce knocking when the motor attempts to move the carriage beyond the point where it has physically stopped.

However, because your knocking occurs specifically near the capping station, I would prioritize the service-station lifting mechanism and conversion-component clearance before replacing carriage electronics.

PW and PE Sensor Problems Can Produce False Paper Jams

The second major possibility is an electronic sensing problem involving the PW and PE systems.

The PW sensor, or paper-width sensor, is associated with the carriage and examines the media area below the printhead. It helps the printer identify paper edges and printable width. Transparent or semi-transparent PET film does not reflect light in the same way as ordinary paper, so the sensor may not receive the signal the original Epson firmware expects.

The PE sensor, commonly called the paper-end or paper-eject sensor, monitors the presence and movement of media through the paper path. Contamination, a displaced sensor flag, a pinched cable, or the optical characteristics of DTF film can cause the printer to believe that the media did not arrive, moved incorrectly, or ended unexpectedly. These conditions may be reported as a false paper jam.

Changing the paper type, thickness, size, and mismatch settings may influence feed timing or error detection, but those settings do not fundamentally redesign how the ET-8550 detects transparent film. The printer was originally engineered to print on supported paper and photo media, not transparent DTF PET film.

This is why software-setting combinations sometimes appear to work temporarily but remain inconsistent. A particular film, room temperature, loading angle, print size, or reflective backing may change the sensor response enough to make one print succeed and the next one fail.

Mechanical Interference Must Be Corrected Before Using a Sensor Override

A sensor-override system should not be used to hide a genuine mechanical collision. If the carriage is striking the capping station, tubing, wiper, or another physical component, that obstruction must be corrected first.

Once the carriage can travel smoothly and the capping station reliably lowers and retracts, then it makes sense to address false readings from the PW, PE, paper-feed, and related sensors.

BCH Technologies offers an ET-8550 DTF Conversion Electronic Control Board Set [https://bchtechnologies.com/collections/kevinv2/products/bch-et-8550-dtf-conversion-control-board-set-film-feed-stabilizer-crpw-override-auto-waste-reset-white-ink-mixer-controller].

This system is designed to stabilize PET-film feeding and electronically correct sensor conditions that can lead to false paper-jam errors. Its film-feed board works with signals associated with the PE sensor, paper cassette sensors, and paper-feed encoder. Its CRPW board addresses carriage and paper-width detection problems caused by differences in film opacity and reflectivity. The set also includes waste-reset and white-ink-management functions. Professional installation is recommended because this is an advanced electronic modification rather than a printer-setting adjustment.

A Practical Diagnostic Order

Based on the symptoms, I would investigate the printer in this order:

First, determine whether the carriage physically knocks against the capping station or another conversion component. Confirm that the service-station platform and wiper lower completely before the carriage passes.

Second, inspect the change gear and transmission slider, especially Gear No. 549 in the exploded-parts guide.

Third, check the DTF tubing, drag chain, dampers, brackets, wiring, and printhead cover throughout the carriage's full range of movement.

Fourth, inspect the CR encoder strip, belt, and pulley system for contamination, displacement, or binding.

Fifth, examine the PE sensor flag and wiring for ink buildup, film scraps, misalignment, or damage.

Finally, after confirming that there is no physical obstruction, consider an electronic sensor-override solution for the PW, PE, and film-feed signals.

Changing additional CadLink or printer paper settings is unlikely to correct a repeatable knocking sound. The sound indicates that the printer is encountering a physical or positional problem, while the inconsistent film detection may represent a second electronic issue.

Addressing printer problems can be complicated because many failures require direct observation, disassembly, and hands-on testing. For that reason, we cannot provide continuing remote troubleshooting or guarantee a repair diagnosis without physically evaluating the machine.

We offer in-person evaluation and repair through our local printer diagnostic and repair facility [https://bchtechnologies.com/printer-repair-service]. Because demand is high, repairs and drop-off appointments are handled on a first-come, first-served basis, and it may take several weeks before an opening becomes available. Our services can cover an entire printer or certain individual components, with instructions provided for the applicable service. We also recognize that professional repair is not always the most economical option.

For that reason, we strongly encourage continued self-help research. You can begin with YouTube or visit the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. On the channel homepage, use the search icon near the About section to search for specific terms such as "ET-8550 capping station," "ET-8550 transmission slider," "ET-8550 false paper jam," "ET-8550 PE sensor," or "ET-8550 DTF control board."

We receive dozens of questions each day asking whether a video exists for a particular repair. After creating printer-repair videos for more than nine years, it is difficult to remember every video by title, so YouTube's channel-search function is usually the fastest way to locate the relevant material. YouTube may also recommend useful demonstrations from other repair channels.

Thank you again for contacting us, for watching our videos, and for providing such a detailed explanation of the symptoms. The consistent knocking sound should give you a strong starting point: confirm that the carriage and capping-station mechanism move freely before attempting to correct the film-sensor signals.