How to Fix Epson ET-8550 Stuck in Inspection Mode After Motherboard Replacement

Question:

I have two Epson ET-8550 printers (I am still unsure why I bought two), and neither will turn on. I did change the motherboard in one of them, but now I get a screen I don’t understand. Please see the pictures below of what I see. Can you tell me how to troubleshoot this?

Answer:

Anyway, regarding your problem, your Epson ET-8550 has been stuck in Inspection Mode since the motherboard replacement. This mode, however, was designed for internal diagnostics and factory testing, so it should not be user-accessible. Under normal circumstances, the printer should not enter this state unless specific diagnostic criteria are accurate.

What Is the Inspection Mode on an Epson ET-8550?

Inspection Mode is a hardware diagnostic function that very few manufacturers are familiar with, and how it is used during the final assembly of the printer to check that all of the hardware is working correctly. This mode is enabled when the printer recognizes that some parts are not connected or are not connected properly when the printer is booting up. It’s not really meant to be available under normal usage.

How to Exit Inspection Mode?

Official instructions for exiting Inspection Mode are available on page 62 of the Epson service manual. However, such a workaround often doesn’t yield reliable results simply because it was never meant to be triggered in the first place. If your printer has entered this mode due to a firmware issue, then following Epson’s exit procedure may not solve the issue.

Possible Causes & Fixes

Below are some common causes of Inspection Mode in your ET-8550, and how to fix them:

Firmware Corruption

If the printer unexpectedly triggered Inspection Mode, the firmware may have become corrupted while replacing the motherboard.

Fix: If the firmware is corrupted, the regular exit procedure cannot be used. You'll most likely have to do an EEPROM rewrite to restore the correct firmware.

Absentee or Incorrectly Placed Materials

Since Inspection Mode gets invoked when critical elements are absent, it’s important to ensure:

Everything properly seated, and all ribbon cables connected.

The control panel and scanner unit have been attached correctly.

All internal sensors and boards are completely wired.

This is assuming the replacement motherboard matches your original and is designed for your specific printer model.

Fix:

Check all the cables again to make sure that there are no loose ribbons or incorrectly put on ribbons.

Scanner and control panel - (disconnect and reconnect your scanner and control panel).

If you replaced the motherboard, ensure it’s a direct match for the ET-8550, rather than from another Epson model.

EEPROM Rewrite Required

Some printers get stuck in Inspection Mode and can't exit normally, which may require an EEPROM rewrite. To get the correct firmware back, you would literally have to reprogram the mainboard.

Fix:

If a local repair technician has access to the equipment, you could consider sending the motherboard away for EEPROM reprogramming.

At BCH Technologies we also perform mainboard repair services to assist with restoring your printers printing function.

Final Thoughts

The nature of repairs makes addressing printer issues a somewhat hands-off approach. Unfortunately we are not able to offer remote troubleshooting for hardware failures or firmware corruption. We do not offer any kind of remote appliance repair service, but we do offer a local (new hope, mn) diagnostic and repair service (https://bchtechnologies.com/printer-repair-service) where you can bring your appliance to our local repair facility, but due to the demand for this service, is completely first-come first-served, and depending on volume may take weeks before we get to evaluating your printer. We have any full printer repair and parts-repair service with full direction how to do it. That said, we know that our rates are not the cheapest.

For more self-repair minded individuals, we strongly encourage you to look up fixes online. Look for troubleshooting videos on YouTube, and you can start with our BCH Technologies YouTube Channel (https://youtube.com/@bchtechnologies) use the search icon (next to "About") of our channel to see videos related to specific topics. As we've produced many repair videos over nine years, catching up on what you need is made easiest by using the search function.

We appreciate your reaching out and thank you for your continued support. Thank you for your understanding and working through all scenarios with BCH Technologies. If you have more questions please check our resources or ask us again.