Printer Faults & Error Codes
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      1. Cyklop Needham Knowledge Hub
      2. CIJ Printer Maintenance & Troubleshooting
      3. Printer Faults & Error Codes

      What causes a charge fault or EHT error on my CM750 printer?

      Understand the most common causes of charge and EHT (high voltage) faults in your CIJ printer, and how to test and fix them before calling support.

      What is a charge fault or EHT error?

      In a CIJ printer like the CM750, ink droplets are electrically charged to allow them to be deflected into position on your product. The charge electrode applies this voltage. If there's any issue with the high-voltage system—such as contamination, blockage, or faulty components—you’ll get a Charge Error or EHT (Extra High Tension) Fault, and your printer will stop marking.

      These errors can seem serious, but most are caused by contamination or component wear and are often fixable without an engineer.

      What causes EHT and charge faults?

      1. Dirty or contaminated charge electrode
        ➤ Ink or dust build-up interrupts voltage transfer.

      2. Nozzle or restrictor partially blocked
        ➤ A weak or unstable ink stream affects charging accuracy.

      3. Faulty or ungrounded high voltage cable
        ➤ Bad connections or insulation failure triggers fault conditions.

      4. Short circuit in the printhead
        ➤ Often due to wet ink bridging components inside the head.

      5. Damaged restrictor or worn insulation
        ➤ Over time, these components degrade and cause current leakage.

      How to fix a charge fault

      ✅ Step 1: Clean the printhead

      • Power off the printer

      • Use Needham-approved cleaning fluid and a lint-free cloth

      • Wipe the charge electrode, nozzle, and deflector plates

      • Let dry fully before powering back on

      ✅ Step 2: Inspect the restrictor

      • Check for clogs or restricted flow

      • If stream looks unstable, run a Clean Ink System or Replace Nozzle Filter

      ✅ Step 3: Check the high voltage (HV) cable

      • Confirm it is securely connected

      • Inspect for damage, cracks, or wear

      • Do not operate the printer with exposed HV cabling

      ✅ Step 4: Test stream and charge

      • Reboot the printer

      • Start ink flow and enter Test Print mode

      • Verify a stable, centred stream is deflecting correctly

      When to escalate

      Call Needham technical support if:

      • Charge or EHT faults persist after cleaning

      • Stream deflects wildly or misses completely

      • The charge electrode or HV system is visibly damaged

      • You hear sparking or see arcing from the printhead

      Pro tips for preventing future faults

      • Clean the head daily in high-use environments

      • Replace nozzle filters and restrictors at recommended service intervals

      • Store printers in clean, dry areas (humidity causes arcing risk)

      • Never run ink that’s expired or outside its recommended spec