ALL-LEDS-FLASHINGMicroline 320 Turbo

All LEDs Flashing on OKI Microline 320 Turbo: How to Fix

Synchronous flashing of all control panel LEDs on the OKI Microline 320 Turbo signifies a Fatal System Error. This occurs when the main logic board fails its initial POST routine, often caused by unstable power rails or printhead short circuits.

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Common causes

  • 1Main logical unit self-test failure (defective RAM, ROM, or corrupt EEPROM state).
  • 2Voltage dropouts or high noise ripple on the internal power supply module.
  • 3A physical short circuit inside the printhead solenoids or the flexible flat carriage ribbon cable.

Solutions

Troubleshooting and Hardware POST Failure Recovery

When the OKI ML 320 Turbo boots, its internal ROM chips test core components like logic gates, driver transistors, and the stepper motor assembly. If any critical test fails, the printer triggers a continuous multi-LED flash state.

  1. Isolate Peripheral Hardware: Disconnect the DB25 parallel cable, network interfaces, or USB connections. Power on the printer standalone to bypass external port loop issues.
  2. EEPROM Cold Initialization: Power down the unit. Press and hold both the SEL and LF buttons. Keep them held down while powering on the printer. Release after the print carriage resets to its home position.
  3. Verify Supply Rail Voltages: Aging electrolytic capacitors on the main power board (delivering critical +35V and +5V lines) can ripple, triggering power-check interrupts that crash the firmware controller.

Steps to follow

  1. 1

    Disconnect Data Cables

    Unplug the parallel, serial, or USB cords to isolate the printer's CPU from computer interface conflicts.

  2. 2

    Perform an EEPROM Hard Reset

    Hold down SEL and LF buttons while switching the power ON to overwrite corrupted volatile RAM space.

  3. 3

    Examine the Head Ribbon Cable

    Check the thin white flat ribbon cable linking the board to the carriage. Verify it has no burns or micro-fractures.

  4. 4

    Check Board Capacitors

    If the problem is persistent, examine the motherboard for blown or bulging power capacitors that require reflow/replacement.

Frequently asked questions

Not necessarily. Often, it is a localized logical lockup or a simple flat cable connection issue that can be fixed without requiring a costly board swap.

Yes. A short circuit in one of the 9 solenoid pins can draw excessive current, prompting the main board's over-current protection system to trip instantly.