Question: I'm using a UV printer with a Knfun EP-4H Print Board V2.1 designed for four XP600 printheads, though I currently have three heads connected. I recently started getting a 7-red-light blinking error and the printer stopped printing. Sometimes, after cycling the power, it will print briefly, but the error returns. Disconnecting the heads one by one didn't help. Can this board be repaired? Also, I have 2-3 XP600 printheads with two or three channels not working-can these be repaired, and what would the cost look like?

Answer:
Understanding the 7-Red-Light Blinking Error on Knfun EP-4H Boards

A 7-red-light blinking error on machines using the Knfun EP-4H V2.1 board usually indicates a communication or control failure between the mainboard and the head board. This type of error can come from multiple sources, and because Knfun provides no public documentation, troubleshooting requires hands-on inspection.

1. Possible Causes of the Blinking Error

Based on your description, the most likely culprits include:

• Fault in the EP-4H head board

The board can be repaired, but the success rate is relatively low due to:

• Lack of manufacturer documentation

• Complexity of a 4-printhead controller

• Limited ability to test without the entire printer

• Sensitivity of multi-head signal processing

Since your printer is too large to ship practically, repairs become limited to components we can safely bench-test.

• Fiber-optic communication issues

This board uses two fiber-optic communication cables between the mainboard and the head board. These fibers often move with the carriage, and:

• Micro-fractures

• Loose connectors

• Signal instability

can all trigger intermittent printing and blinking-light errors.

• Power-supply instability

The EP-4H uses its own dedicated PSU. A failing or unstable PSU can cause brief periods of printing followed by shutdown errors.

• Encoder strip or sensor issues

If the printer momentarily prints after being restarted, consider checking:

• The encoder strip for contamination

• The encoder sensor for dust or ink mist
  A misread encoder may cause the board to halt operation.

• Mainboard communication failure

Check the PC side as well-look for:

• USB communication drops

• Driver crashes

• Error logs in the RIP software

Communication interruptions can cascade into red-light blinking errors.

Can the Knfun EP-4H Board Be Repaired?

Yes, it can be repaired, but with important limitations:

• Success rate is modest due to lack of schematics

• Some failures cannot be tested without the entire printer

• Board-level faults involving fiber communication drivers are difficult to restore reliably

That said, if the board is not physically burned and the components are identifiable, repair is sometimes possible.

Repairing XP600 Printheads With Failed Channels

For your XP600 printheads with 2-3 dead channels, we do offer a full multi-stage repair service. Below is a detailed explanation of how our process works.

BCH Technologies XP600 Printhead Repair Process

Step 1: Initial Electronic Test (Test-1)

Purpose:
Determine whether the printhead is electronically functional and safe to work on.

What We Do:

• Measure resistance of all circuits

• Check for shorts, open lines, overheating, or abnormal thermal signatures

• Ensure the head will not damage your printer once reinstalled

Process:
Customers ship their printheads to us.
We test them and send a full electronic report showing pass/fail status.

Turnaround: 1-3 business days after receiving the printheads
Shipping: Customer covers all shipping costs (to and from BCH Technologies)

Step 2: Mechanical & Nozzle Evaluation (Test-2)

Purpose:
Assess internal mechanical viability and determine whether the head can be restored.

What We Do:

• Perform deep internal cleaning

• Remove nozzle plate

• Inspect Piezo chip and membrane

• Examine nozzle array microscopically

• Count damaged nozzles

Important:

• Printheads failing Step 2 are not returnable, because disassembly renders them non-functional.

• Only heads that pass will move forward to restoration.

Step 3: Printhead Restoration

Purpose:
Restore stable ink output and channel integrity.

What We Do:

• Nozzle-to-nozzle cleaning

• Internal channel rehabilitation

• Re-glue and align nozzle plate

• Final electrical and print-pattern testing

Turnaround for Steps 2 & 3:
Approximately 4-6 weeks, depending on condition and workload.

Payment:
Only charged for units that qualify for repair after Steps 1-2.

Disclaimer:
Repairs are best-effort only.
Print quality, long-term stability, and full recovery of all channels cannot be guaranteed due to previous damage or uncontrollable factors.

Important Note About Remote Troubleshooting

Addressing printer problems-especially with large UV machines-is a hands-on process. Because of this, we're not able to provide remote diagnostic or repair guidance. We do offer in-person evaluations through our local facility at BCH Technologies Printer Repair Service (https://bchtechnologies.com/printer-repair-service). Due to high demand, repairs are processed on a first-come, first-served basis, and wait times can be several weeks.

Our services cover both complete printers and individual components, and we provide clear instructions for drop-off. However, as our rates may not be the most economical, we strongly recommend starting with self-help research-whether through general online resources or our BCH Technologies YouTube channel (https://youtube.com/@bchtechnologies). Use the search icon on the channel's homepage to find videos by topic. With nine years of content and many daily inquiries, searching is the fastest way to locate relevant information, and YouTube may also recommend helpful videos from other creators.

Thank you again for reaching out to us. We truly appreciate your patience, your engagement, and your continued support. If you have any further questions, feel free to contact us anytime.