Troubleshooting Epson 1390 Printers: Why Your Mainboard Keeps Burning Out or Prints Blank

Understanding the Root Cause of Mainboard Failure

When working with Epson 1390 printers, one of the most frustrating problems you might encounter is a mainboard that either burns out or refuses to print anything. Even after replacing the mainboard and printhead, and installing new FFC cables, you might still find that every test print comes out blank.

This issue is common among users who are replacing parts without realizing that the root cause may not be the printhead or the mainboard itself. In many cases, the real culprit is a small but critical component - the board connected to the CN15 port on the mainboard. When this particular board fails, it can cause irregular electrical behavior that leads to recurring mainboard failures or a constant ink light warning.

Recognizing the Common Symptoms

When the CN15-connected board is faulty, your printer will begin to display some very distinct symptoms. Here are the most common signs:

• Persistent Ink Light: Upon powering on the printer, the ink light stays on continuously, even after replacing the mainboard.

• Error Messages: Diagnostic tools or adjustment programs may display messages such as "Ink not detected" or "Ink cartridge error."

• Repeated Mainboard Failure: Every new mainboard installed either burns out quickly or shows no printing response at all.

These symptoms are strong indicators that the board connected to CN15 is damaged or shorted.

Using a Multimeter for Diagnosis

Before replacing another expensive mainboard, take a few minutes to test the electrical continuity of the CN15-connected board. Using a multimeter in continuity (beep) mode, you can verify whether any pins are shorted.

Set the multimeter to the mode where it emits a beep when the red and black probes are connected. Place the probes on pin 1 and pin 2 of the suspect board.

• If the multimeter beeps: The pins are shorted, which means there is a direct electrical connection that shouldn't exist. This condition can cause the mainboard's F1 fuse to blow or even damage the driver board.

• If the multimeter doesn't beep: The connection between the pins is open, and the short circuit is not present at that point.

If a short is detected between pin 1 and pin 2, installing the board will likely damage your mainboard again. It's best to stop immediately and replace the faulty component before proceeding further.

Inspecting for Burn Marks and Damaged Components

If you've already experienced a burned-out mainboard, it's essential to perform a visual inspection of your boards and cables. In many cases, you can identify the problem simply by looking at the condition of the pins or the nearby resistors.

Inspect pins 1-4 carefully:

• Pins 1 and 2: These are often the first to show heat damage if there's a short circuit.

• Pins 3 and 4: Severe burn marks here typically indicate that a resistor on the board has been blown out.

When you trace the path of pins 3 and 4, you might find a resistor that is completely burned. This resistor acts as a protective component, and once it fails, it interrupts the circuit, causing erratic printer behavior.

If you notice any burnt areas, discolored resistors, or melted traces, it's a clear sign that the board needs replacement.

Choosing the Right Replacement Board

Not all replacement boards are made equal. If you purchase a generic CSS board that doesn't include an override function, it may fit your printer but won't resolve your issue. These standard boards often lack the proper circuitry to communicate with the printer's mainboard correctly, leading to continuous ink detection errors.

At BCH Technologies, you can find a 1390 Cartridge Chip CSS Override Board designed specifically to prevent these recurring problems. Unlike blank CSS boards, this model features both the original board and an override board welded on.

This design ensures:

• Better electrical stability

• Reduced risk of mainboard burnout

• Proper communication between the cartridge system and mainboard

Keep in mind that while the override board prevents mainboard burnout, it may still show an "Ink Out" status if the resistor or chip damage has already occurred. In such cases, replacing both the override board and related cables is the best solution.

You can find the appropriate replacement parts and accessories at bchtechnologies.com.

Preventing Future Failures

Once you've replaced the faulty board and verified there are no shorts, you can take several steps to prevent the issue from recurring:

1. Test Before Installing: Always use your multimeter to test continuity between pins before connecting the board to the mainboard.

2. Inspect FFC Cables: Damaged or burned flat cables can cause shorts that propagate through the mainboard.

3. Avoid Static Electricity: Ground yourself before handling sensitive boards to prevent static discharge damage.

4. Use Genuine Components: Invest in high-quality parts from reliable sources like BCH Technologies to avoid counterfeit or substandard components.

5. Keep the Work Area Clean: Dust and moisture can lead to unintended electrical connections that trigger shorts.

By incorporating these practices into your repair routine, you can significantly reduce the risk of mainboard failure and prolong the life of your printer.

Understanding How This Impacts Your Printer's Performance

When the CN15 board or its related circuitry fails, the printer's entire communication system can become unstable. The printer relies on accurate signals from the cartridge chip board to determine ink levels and cartridge presence.

A damaged resistor or shorted pin can confuse the printer, making it believe there is no ink even when the cartridges are full. Over time, this miscommunication can trigger error loops or cause the printer to stop responding altogether.

By identifying and fixing the shorted connections, you restore the proper data flow between the printhead, the cartridge chip, and the mainboard. This not only revives your printer's ability to print but also ensures that your mainboard stays protected in the long run.

Wrapping It Up

If your Epson 1390 keeps burning mainboards or printing blank pages despite multiple replacements, the problem likely lies in the small but critical board connected to CN15. Shorted pins or burned resistors can silently damage the mainboard each time you power the printer on.

Testing with a multimeter and replacing the faulty CSIC override board can prevent costly component damage and restore your printer's functionality. Always source reliable parts from BCH Technologies to ensure your repair lasts.

We have a video below demonstrating how to test and identify the faulty board - watch it to see each diagnostic step in action and learn how to safely repair your printer.