Epson ET-4750 Not Recognized by Recovery Firmware: Why Printer Inspection Mode May Not Mount Over USB

Question

I watched your video about solving Epson printers stuck in recovery mode and fixing firmware errors. My Epson ET-4750 is in printer inspection mode, but the recovery firmware does not recognize the printer when it is connected by USB. I tested another working ET-4750 using the same USB cable and computer, and that printer is recognized by the recovery firmware and appears as available for downgrade. What could be causing the problem?

Answer

Since you tested another working Epson ET-4750 with the same USB cable and the same computer, and that second printer was detected by the recovery firmware, that tells us something important. The USB cable, USB port, and recovery software are probably working. The problem is more likely related to either how the computer is assigning the USB printer port to the problem printer, or how the problem ET-4750 is presenting itself to the computer while it is in printer inspection mode.

One common cause is that the computer has already seen too many Epson printers in the past. Even if you remove old printers from Windows or from the printer list, the virtual USB printer ports may still remain in the system. These leftover ports can continue occupying port numbers in the background. As a result, when you connect a new printer, the computer may assign it to a very high-numbered virtual USB port, or it may not mount the printer in a way that the Epson firmware recovery tool can see.

This matters because Epson's firmware recovery tool does not always scan every possible port on the computer. In some cases, if the virtual port number is higher than 62, the firmware tool may not detect the printer. Epson seems to assume that most users will not have more than 62 printers or virtual printer ports installed, so the utility may only scan the first 62 ports. If your computer has accumulated many old Epson ports, the printer may technically be connected, but the recovery firmware still may not list it.

To check this, you can try using a cleaner computer that has not had many Epson printers installed before. A fresh Windows computer or a computer with fewer printer drivers and fewer old USB printer ports may detect the ET-4750 more easily. You can also remove old Epson printer drivers, old printer queues, and unused virtual USB printing ports from Windows, but this can be time-consuming and must be done carefully. Simply deleting the printer icon is often not enough because the port and driver package may still remain.

Another possible issue is that the printer's recovery mode may not allow the printer to mount correctly on the computer. There is a difference between a printer being powered on, a printer being in firmware recovery mode, and a printer being in inspection mode. The computer can only see the printer if the printer's firmware is allowing it to identify itself through USB. If the printer is in a state where the USB interface is not fully active, the firmware tool will not see it, even though the printer is physically connected.

Printer inspection mode can be especially tricky. Inspection mode is generally intended for factory or service use. It is not always the same as normal recovery mode. In the factory, the printer may enter different stages of inspection depending on what has been assembled, tested, or programmed. If the printer is in an inspection stage where the computer connection is not required, the printer may not mount itself as a USB device at all. In that case, the recovery firmware cannot recognize it because the printer is not presenting itself to the computer in a normal firmware-update-ready state.

This also explains why your second ET-4750 is detected but the problem ET-4750 is not. The working ET-4750 is likely entering a normal USB-recognizable state, so the firmware recovery program can see it. The problem ET-4750 may be in a different internal mode, such as inspection mode, incomplete recovery mode, or a firmware state where USB firmware communication is blocked or unavailable.

Another possibility is that the firmware already inside the printer is marked as not upgradeable or not downgradeable. Epson firmware packages often check the printer model, firmware version, region, firmware ID, and update rules before allowing the firmware process to continue. If the firmware currently loaded in the printer is marked in a way that does not allow upgrade, downgrade, or recovery through the normal tool, the recovery utility may refuse to show it as an available target. Sometimes the printer is visible to the operating system but still not visible to the firmware tool because the tool decides it is not a valid device for that firmware package.

You should also check whether Windows makes any sound or shows any device change when the problem ET-4750 is plugged in. If Windows does not react at all, the printer may not be mounting over USB. That could point to inspection mode, a USB interface problem, a damaged USB port, a mainboard communication issue, or a firmware state that prevents USB enumeration. If Windows reacts but the recovery tool still does not show the printer, then the issue is more likely related to Epson's firmware utility, virtual port numbering, driver assignment, or firmware compatibility.

It is also worth checking Device Manager. If the printer appears as an unknown USB device, USB composite device, Epson device, or printer device with an error, that gives a clue. If it appears with a warning sign, the driver may not be loading correctly. If it appears and disappears repeatedly, the printer may be restarting, failing USB initialization, or stuck in a partial firmware state. If it does not appear at all, then the printer is probably not presenting itself to the computer.

Here are the most likely causes in your case:

The first possibility is that the computer has accumulated too many previous Epson printer installations. Even if those printers were removed, their virtual ports may still exist. If the ET-4750 is assigned to a virtual port higher than what the Epson recovery firmware scans, the printer may not appear in the firmware tool.

The second possibility is that the virtual printer port number is above Epson's scanning range. If the port is mounted past 62, the firmware tool may not see it because it may only scan the first 62 ports.

The third possibility is that the printer's recovery mode is not mounting the printer correctly on the computer. Recovery mode must still allow USB communication. If it does not, the firmware utility will not detect the printer.

The fourth possibility is that inspection mode is preventing USB mounting. Since inspection mode is intended for factory/service use, the printer may not behave like a normal consumer printer. If the inspection stage does not require a computer, the printer may not mount itself to the computer at all.

The fifth possibility is that the firmware already inside the printer is marked as not upgradeable or not downgradeable. In that case, the firmware utility may not list the printer as an available device even though the printer is connected.

If you want to narrow it down, I would first test the printer on a different computer that has not been used with many Epson printers. Use a direct USB connection, not a USB hub. Also try a different USB port on the computer. If the printer still does not appear, then the issue is more likely inside the printer's firmware state, inspection mode status, USB communication circuit, or mainboard. If it appears on the cleaner computer, then the original computer likely has a virtual port or driver conflict.

You can also compare what happens when connecting the working ET-4750 and the problem ET-4750. If the working printer appears in Device Manager and the problem printer does not, then the issue is not the recovery program alone. The problem printer is not mounting correctly. If both appear in Device Manager but only the working printer appears in the recovery firmware tool, then the issue may be firmware compatibility, port assignment, or Epson's update tool restrictions.

Unfortunately, when a printer is in inspection mode instead of normal recovery mode, the solution is not always the same as a typical "stuck in recovery mode" case. Recovery firmware tools are designed to communicate with the printer only when the printer exposes the correct USB firmware interface. If the printer is trapped in a factory inspection state that does not expose that interface, the normal downgrade or recovery utility may not be able to reach it.

Addressing printer issues can be a complicated affair because many of these problems require hands-on diagnosis. For that reason, we are 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 diagnostic facility: BCH Technologies Printer Repair Service [https://bchtechnologies.com/printer-repair-service]. Because demand is high, we operate on a first-come, first-served basis, so it may take a few weeks before we can accept your printer for drop-off. Our services are structured to repair either a whole printer or specific parts, with clear instructions on how to proceed. However, we understand that our rates may not be the most economical option for every situation. Therefore, we highly recommend self-help through online research whenever possible. You can begin by checking YouTube or visiting our YouTube channel homepage: BCH Technologies on YouTube [https://youtube.com/@bchtechnologies]. Once you are on the channel page, use the search icon next to "About" on the right-hand side of the menu bar to search for your specific model, error message, firmware issue, or repair topic. We receive many questions every day asking which video covers a specific topic, and after creating videos for many years, it is difficult to remember every single one. YouTube's search function is usually the fastest way to locate a related video, and YouTube may also suggest helpful videos from other repair channels.

Thank you again for contacting us and for watching our videos. We appreciate your support and hope this explanation helps you understand why the ET-4750 in inspection mode may not be recognized by the recovery firmware, even when another ET-4750 works with the same USB setup.