How to Fix Transportation Lock Error on Epson ET-8550 When the Printhead Sits Too Low

Question:
I'm experiencing a "Transportation Lock" error on my Epson ET-8550. However, I don’t think the issue is related to the ink tubes. From what I can tell, the printhead looks like it's sitting too low. Do you have any suggestions or fixes for this? I’m also open to purchasing any necessary parts from you. Thanks!
(Original reference: Watch video)

Answer:
Thank you for reaching out to us, and we sincerely apologize for the delay in getting back to you. We understand how time-sensitive printer issues can be, and we also believe that every question deserves careful attention and a detailed response. At BCH Technologies, we truly appreciate your continued support—especially on our YouTube channel (https://youtube.com/@bchtechnologies). Your feedback helps us grow our expertise and develop better resources for the entire community.

Now, regarding the "Transportation Lock" error you’re encountering on your Epson ET-8550—yes, after reviewing your video, it indeed appears that the printhead is sitting too low. This is a crucial observation, and you're absolutely right to question the ink tubes' involvement, as the issue here likely lies elsewhere.

A common cause for this problem is a misaligned or worn APG (Automatic Platen Gap) unit. The APG system automatically adjusts the gap between the printhead and the platen (the surface the paper rests on). When this mechanism is off—either due to a misalignment, wear, or incorrect initial calibration—it can cause the printhead to rest too close to the platen. This will not only trigger the "Transportation Lock" error but can also result in smudging or head strikes on the paper.

To resolve this, you’ll need to verify and, if necessary, manually set the platen gap. We’ve created a reference guide specifically for the ET-8550, which includes details on how to set this gap properly. Please refer to page 150 of our ET-8550 Reference Guide (https://bchtechnologies.com/products/reference-for-ecotank-8550).

The recommended gap is between 1.3 to 1.4 mm. You’ll need a measuring tool or makeshift gauge to set this correctly. Here are a few everyday items you can use to approximate the correct thickness:

• A U.S. dime – approximately 1.35 mm thick (ideal).

• A standard credit card – around 0.76 mm, so stacking two cards will get you close to 1.5 mm.

• Standard copy paper – roughly 0.1 mm thick per sheet, so you’d need about 13 sheets to reach 1.3 mm.

Once you adjust the platen gap to the proper height, the printhead should rise to the correct level, and the printer will likely stop displaying the "Transportation Lock" error—assuming no other mechanical issues are present.

Troubleshooting printer hardware issues can be particularly tricky, as they often require hands-on inspection and adjustment. For this reason, we're unable to provide remote repair services or detailed step-by-step tech support. However, we do offer in-person evaluation and repair through our local diagnostic facility (https://bchtechnologies.com/printer-repair-service). Please note that we work on a first-come, first-served basis, and due to high demand, wait times for drop-off appointments may extend for several weeks.

Our services can target specific printer parts or full-machine repairs, and we’ll provide you with detailed next steps based on your issue. That said, we understand that our rates may not be the most budget-friendly, so we highly encourage DIY troubleshooting using online resources. Our YouTube channel (https://youtube.com/@bchtechnologies) is a great starting point. To find a specific video, click the search icon located next to the "About" tab on our channel page. With hundreds of videos produced over the years, even we rely on the search bar to find what we need—plus, YouTube may recommend additional videos from other creators that could also be helpful.