How to Troubleshoot a Dead Epson WF-7710 / WF-7720 After Cleaning or Power Cycling

Question:
I have an Epson WF-7715 printer that hasn't been used for a while. I took out the printhead, cleaned it with alcohol, dried it, and reassembled the printer. Then I put the refillable cartridges back in and started purging the ink by printing high-detail pictures. It was working, but the prints weren't perfect yet. I turned the printer off for the night, but the next morning it had no lights and wouldn't power on. I checked your video about testing the power supply, followed the steps, and got the same output voltage. I even checked the motherboard fuses (F1-F4), and they all have continuity. After reassembling, the printer still doesn't turn on-no blue light, nothing. What could be causing this?

Answer:

Let's go through what could be happening with your Epson WF-7715 (also applies to WF-7710 and WF-7720).

1. Verify the Power Supply Output

You mentioned testing the power supply and obtaining the same voltage output as in our video tutorial (Testing Epson WF-7710/7720 Power Supply). That's a great first step. The expected output is about 42V DC when measured across the power connector pins. If the voltage matches and is stable, your power board is likely fine.

However, even a working power supply can fail under load. Try connecting a small load (like a 12V test light or resistor through a voltage divider) to see if the supply voltage drops drastically. If it does, the power board might still be defective despite showing the correct voltage without a load.

2. Check the Motherboard Fuses (F1-F4) and Voltage Rails

It's good that you confirmed continuity on the F1-F4 fuses. These protect the printer's logic circuits and motor drivers. Continuity alone, however, doesn't confirm active voltage. After reassembly, plug in the printer and carefully measure the voltage at the fuses.

• F1 typically carries 42V.

• F2-F4 often regulate or distribute 24V and 5V circuits.

If you're not getting proper voltage across these points, check for broken traces or a failed voltage regulator (often labeled as U1 or IC3 near the fuses).

3. Inspect the Power Button and Front Panel Ribbon

Sometimes, the issue isn't the board itself but the front control panel ribbon cable. If that ribbon is not fully seated or is slightly oxidized, the printer won't power on-no lights, no sounds. Remove it, clean the contacts gently with isopropyl alcohol, and reinsert it firmly.

4. Static Discharge or Short-Circuit Events

After head cleaning and disassembly, it's common for a static discharge or residual moisture to cause a short. Even a small amount of conductive fluid left on the ribbon connectors can trigger a protection circuit. If this happened, the logic board might have entered a fail-safe mode or blown a microfuse that isn't externally visible.

If the printer was unplugged overnight and then became unresponsive, it's possible a standby capacitor discharged and revealed a weak regulator or failed transistor on the motherboard.

5. What to Do Next

• Unplug the printer completely for several hours to allow full discharge.

• Recheck the power cable and AC input fuse (located near the power inlet).

• If the printer remains dead, consider testing the main logic board by substituting it with another from a donor unit-this is often the fastest diagnostic method.

If no lights appear even after a verified power supply and clean ribbon connections, the main logic board (motherboard) is most likely at fault. In that case, replacement or component-level repair (using a bench power supply and multimeter) may be required.

Addressing printer issues can be a complicated affair due to the hands-on nature of the problems. That's why we're unable to provide remote troubleshooting, suggestions, or support for printer repairs. We do, however, offer in-person diagnostic and repair services through our local diagnostic facility (https://bchtechnologies.com/printer-repair-service). Due to high demand, services are provided on a first-come, first-served basis, and it might take a few weeks before your printer can be examined. We can repair either the entire unit or specific parts, depending on your needs. If you prefer to troubleshoot on your own, we recommend starting with online resources-particularly our BCH Technologies YouTube channel (https://youtube.com/@bchtechnologies). Use the search bar next to "About" on our channel page to locate videos on related topics.

Thank you again for your patience and for being part of our BCH Technologies community. Your engagement helps us continue producing educational content and advancing printer repair knowledge for everyone.