Epson WF-3640 Error 0x9A, F1 Fuse Blown, and Persistent ADF Paper Jam Error After Mainboard Replacement

Question:

I replaced the mainboard on my Epson WF-3640 because it originally showed error code 0x9A and had a blown F1 fuse. After replacing the board, the 0x9A error is gone, but now every time the printer boots up, it shows a paper jam in the ADF (Automatic Document Feeder). I've checked thoroughly and there's no paper anywhere in the printer. I've also removed the ink cartridges and inspected everything I can see. Is there anything else I might have overlooked?

Answer:

Step 1: Understanding the Original Error - 0x9A and F1 Fuse

On the Epson WF-3640, error code 0x9A is typically a fatal hardware error. In many cases, it is related to:

• Printhead electrical failure

• Shorted printhead

• Mainboard driver IC failure

• Blown F1 fuse due to overcurrent from the printhead

You mentioned the F1 fuse was blown, which is extremely important. On Epson printers, the F1 fuse protects the printhead drive circuit. When the printhead internally shorts, it draws excessive current, and the F1 fuse blows to prevent further damage to the mainboard.

Replacing the mainboard removes the 0x9A error only if the short condition is no longer present.

However, if the original cause of the blown fuse was a burnt or shorted printhead, installing a new board without replacing the printhead can create secondary issues.

That's why my direct answer is:

👉 Your printhead is likely burnt.

Here's why.

Step 2: Why You're Now Getting an ADF Paper Jam Error

After replacing the mainboard, the printer now boots but shows a constant ADF paper jam error, even though there's no paper inside.

This situation commonly happens when:

• The mainboard is functional

• But the printhead is electrically damaged

• And the firmware fails during initialization

During startup, the printer performs a sequence:

1. Mainboard power-up

2. Printhead electrical check

3. Carriage movement check

4. Sensor initialization (including ADF sensors)

If the printhead has internal short circuits or damaged nozzles, the printer may:

• Fail during head initialization

• Misread sensor states

• Display unrelated errors such as "ADF paper jam"

This is what we call a false front-end error masking a deeper electrical fault.

In many WF-3640 cases, once the F1 fuse blows due to a shorted head, replacing only the mainboard doesn't fix the root cause. The new board may not immediately blow again, but the damaged printhead still causes abnormal electrical readings.

Step 3: What You Should Check Next

Here are the specific things I recommend checking:

1. Inspect the Printhead Cables (FFC Cables)

• Ensure all ribbon cables are fully seated.

• Look for bent pins or damaged traces.

• Make sure no cable is inserted backwards or partially loose.

A misaligned printhead cable can also trigger sensor errors.

2. Disconnect the Printhead (Test Boot Without Head)

If you're comfortable doing this:

• Disconnect the printhead cables.

• Power on the printer.

If the error changes (for example, to a different fatal error or head missing error), that confirms the head circuit is involved.

If the same ADF jam error persists even with the head disconnected, then we'd look deeper into:

• ADF sensor flags

• ADF motor driver

• Mainboard compatibility (correct firmware version)

3. Check the ADF Sensor Flags Physically

Even though there's no paper, check:

• ADF input sensor flag

• Exit sensor flag

• Broken or stuck plastic actuators

• Spring tension on the ADF mechanism

Sometimes during disassembly for board replacement, a small plastic sensor lever gets dislodged.

4. Verify Mainboard Revision Compatibility

WF-3640 boards sometimes have different firmware revisions depending on region. If the board firmware doesn't match:

• Scanner firmware

• ADF firmware

• Control panel firmware

It can throw initialization errors.

Why I Strongly Suspect the Printhead

Here's the key technical pattern:

• Error 0x9A

• Blown F1 fuse

• Board replaced

• New unrelated sensor error appears

This pattern almost always points back to a shorted or burnt printhead.

When a printhead overheats internally, it can damage:

• Nozzle driver resistors

• Internal heater elements

• Driver transistor pathways

Even if it doesn't immediately blow the new fuse, it can create unstable signals that confuse the startup diagnostics.

Replacing the printhead is usually required in these cases.

Important Service Notice

Addressing printer issues can be a complicated affair due to the hands-on nature of these problems. Because of that, we're unable to provide remote step-by-step troubleshooting or live repair guidance.

We do offer in-person diagnostic and repair service through our local repair facility at BCH Printer Repair Service (https://bchtechnologies.com/printer-repair-service). Due to high demand, we operate on a first-come, first-served basis, and it may take a few weeks before we can accept a drop-off. Our services are structured to repair either a complete printer or specific components, with clear procedures on how to proceed.

That said, we understand our repair rates may not be the most economical option. We strongly recommend self-research and learning through online resources. A great starting point is YouTube, especially our channel at BCH Technologies YouTube Channel (https://youtube.com/@bchtechnologies). Use the search icon next to the "About" tab on the right-hand side of the menu bar to look for specific repair topics.

I receive dozens of questions daily about whether we have videos on certain repairs. After creating content for over nine years, it's difficult to remember every video. Using YouTube's search function is the fastest way to locate relevant material. YouTube may also suggest helpful videos from other experienced repair technicians.

Again, thank you very much for your support and for sharing your repair experience. Cases like yours help the entire repair community learn and grow. We truly appreciate your engagement and hope this gives you a clear direction on what to check next.