- Quick Quote
- +86 18295370559
- +86 18295370559
- Email: info@cncfixtech.com
Recently, we received a FANUC 0i-MF control unit from a customer who reported an unusual problem during machine startup.
According to the customer, the CNC system would power on normally, but the screen constantly jumped between pages, making the machine difficult to operate. Even more concerning, several keys appeared to be pressed automatically without any user input.
Because random key activation can potentially alter machine settings or parameters, the customer decided to send the control unit to us for inspection and repair.
In this article, we’ll share the complete troubleshooting and repair process of this FANUC 0i-MF screen jumping and automatic key pressing issue.
After receiving the unit, our engineer powered it on to verify the customer’s complaint.
The problem appeared immediately.
The display continuously switched between screens, almost as if someone was repeatedly pressing keys on the control panel. Several buttons were being triggered automatically, making normal operation impossible.
At this stage, we knew that the issue was likely related to the keypad circuit, but before beginning any repair work, there was one important task that had to be completed first.
Whenever we receive a FANUC control unit with unstable operation, protecting customer data is a top priority.
Although the screen was still jumping and the keys were activating randomly, our engineer attempted to back up all parameters before proceeding with further diagnosis.
The process was not easy. During the backup operation, the display continued to behave erratically, creating uncertainty about whether the operation would complete successfully.
Fortunately, the parameter backup was completed without data loss.
With the customer’s parameters safely stored, we could move forward with the repair process.
The next step was to remove the main board and perform a detailed visual inspection.
After disassembly, an unusual area immediately caught our attention.
Near the lower-right corner of the board, visible contamination and corrosion could be seen around several electronic components. The affected area appeared significantly dirtier than the rest of the board.
Based on our experience, this type of contamination is often caused by coolant mist, oil vapor, dust, or metal particles entering the control cabinet during long-term machine operation.
Over time, these contaminants can accumulate on the PCB surface and gradually cause corrosion.
Interestingly, the contaminated area was located directly around the keypad control circuit.
At this point, we had found our primary suspect.
Further inspection confirmed that the corrosion had affected the circuit responsible for processing keypad signals.
When corrosion develops around fine-pitch electronic components, it can create leakage paths between signals or interfere with normal communication between the control chip and the system.
As a result, the controller may incorrectly interpret signals and behave as if keys are being pressed continuously.
This perfectly matched the symptoms observed during testing:
The root cause of the FANUC screen jumping issue had finally been identified.
With the fault location confirmed, our engineer began the repair work.
First, the contaminated area was thoroughly cleaned to remove corrosion residue and surface contaminants.
Next, the keypad control chip was carefully removed from the PCB.
After removal, the solder balls beneath the chip were rebuilt through a reballing process. Once the chip and PCB pads were properly prepared, the component was soldered back onto the board.
After completing the rework, the entire repair area was inspected again to ensure reliable solder joints and clean signal paths.
For more real repair cases and technical insights, check out our YouTube channel
The repaired main board was then reinstalled into the FANUC 0i-MF controller for testing.
This time, the results were immediately noticeable.
The display remained stable without any unexpected screen changes.
All keypad functions responded normally.
No automatic key pressing occurred during operation.
To ensure long-term reliability, additional functional tests were performed, and the control unit continued to operate normally throughout the testing process.
The fault had been completely eliminated.
This FANUC 0i-MF repair case demonstrates how contamination and PCB corrosion can lead to unusual symptoms such as screen jumping and automatic key pressing.
Although the fault initially appeared to be a software or keypad issue, the actual cause was corrosion affecting the keypad control circuit on the main board.
By identifying the affected area, cleaning the board, and reworking the keypad control chip, the unit was successfully restored to normal operation.
If your FANUC CNC system is experiencing screen jumping, keypad malfunction, display flickering, communication errors, or other hardware-related faults, professional diagnosis can help identify the root cause and reduce machine downtime.
Our team specializes in the repair and testing of FANUC control units, main boards, servo drives, spindle drives, power supplies, encoders, and other industrial automation components.
Feel free to contact us for repair evaluation and technical support.
How we process your repair requirements
Get in touch with us and provide as much detail as possible about the issue you are experiencing.
Our professional repair team will help assess the severity of the problem and the possibility of repair.
The customer sends or delivers the servo drive to our company. We register it in our system and prepare it for further inspection.
Our engineers diagnose the fault points of the servo drive and provide a detailed inspection report, including the final repair cost and estimated repair time.
We provide the repair quote to the customer and wait for their confirmation. If the customer agrees to the quote, we proceed with the repair.
Upon customer approval, we carry out the necessary repairs. After repairs are completed, we perform tests with the motor and conduct aging tests to ensure the servo drive operates reliably under various conditions. Once the testing is successful, we register the drive for delivery.
The customer completes the payment, and we deliver the repaired servo drive to the customer.
We provide attentive follow-up service to ensure customer satisfaction and address any further needs.
