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Phrozen Sonic: the LCD shows no image, flickers or the UV light looks weak (LCD test)

Guide based on the manufacturer's official documentation; usi3d has not yet verified it on a machine.

Technology: Resin · Brand: Phrozen · Symptoms: The LCD screen or UV light does not light up · Updated on 9 October 2026

Symptom

On a Phrozen Sonic, the LCD flickers or glitches, looks dim or does not light up, or in the LCD test the image on the screen does not match the touch panel or spots appear.

Likely causes, from most to least likely

  1. The LCD ribbon cable is loose or badly seated, or damaged near its ends.
  2. The LCD cracked after an incident during a print: it must be replaced.
  3. Burnt LEDs (COB), or red and black wires loose in the LED terminal blocks (on the Sonic Mini 8K, one is on the mainboard and two on the LED driver board).
  4. A power adapter that is not the original or does not have the right rating (on the Sonic Mini 8K, 24 V and 2.5 A).

Checks to tell which one it is

  • Without the vat, run the LCD test: on the Sonic Mini 8K, TOOLS → LCD TEST (the LCD must show the touch panel's shape); on the Mighty 12K, Settings → System → Hardware Testing → LCD TEST: fully lit without black spots, blackened without light spots and a grid matching the panel.
  • Do a dry print: with no vat or build plate, start a sliced file from the USB drive and check whether the LCD image matches the panel and whether it flickers.
  • During the LCD test, take a photo of the LED chip (COB) to look for burnt LEDs, without looking straight at the UV light.
  • Check the label on the power adapter.

Before you start

Uncured resin irritates skin and eyes: wear nitrile gloves and safety glasses, ventilate the room and do not look at the UV light. Before taking anything apart or cleaning it, switch the printer off and unplug it, unless a step says otherwise. If in any doubt, stop and ask a professional.

Step-by-step fix

  1. LCD test and dry print

    Run your model's LCD test and the dry print described in the checks. Do not look straight at the UV light.

    Check: The LCD image matches the panel, without spots or flicker.

    If that does not fix it: If it fails, check the LCD cable (next step).

  2. Reseat the LCD ribbon cable

    Switch off and unplug the printer, place it on a flat surface and open the case (on the Sonic Mini 8K, with the 4 bottom case screws). Open the connector clips on the mainboard and on the LCD, remove the cable, push it fully back in with the pins facing down and lock the clips. Close the case and repeat the LCD test. Also check the cable for damage near its ends.

    Check: The LCD displays the image normally.

    If that does not fix it: Look for cracks in the LCD (next step).

  3. Look for cracks in the LCD

    Remove the LCD frame tape and check the surface, especially edges and corners.

    Check: There are no cracks.

    If that does not fix it: If the LCD is cracked, it must be replaced: contact Phrozen support.

  4. Check the LEDs (Sonic Mini 8K)

    If the LCD looks dim or does not light up: switch off and unplug, remove the UV cover, vat and build plate, carefully lay the printer down and open the bottom case. Unplug the green LED connector from the mainboard, look for burnt LEDs on the chip under the black hood and, with a flat screwdriver, re-secure any red and black wires that have come out of the three terminal blocks. Reassemble, switch on and light the LED with LCD TEST or VAT CLEANING.

    Check: The LCD is back to its normal brightness.

    If that does not fix it: Check the power adapter (next step).

  5. Use the right adapter

    Use the original Phrozen adapter with your model's rating (on the Sonic Mini 8K, 24 V and 2.5 A): another adapter can stop the LED from lighting properly.

    Check: The LED lights normally.

    If that does not fix it: Contact Phrozen support with photos or videos of the LCD test, the cable connection and the screen edges.

Prevention

  • Run the LCD test before printing or as soon as you notice a fault.
  • Do not look straight at the UV light during the tests.
  • If there has been an incident during a print, check the LCD for cracks.

Still not fixed?

Tell usi3d's AI about your case: choose your printer, describe what you see and add photos if you like. It proposes checks step by step, with their sources.

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Printers it applies to

Phrozen's resin printers: Sonic Mega 8K S, Sonic Mighty 8K, Sonic Mighty 12K and Sonic Mini 8K S.

Official sources

This guide summarises the official documentation linked here:

This guide is general information: usi3d has summarised it from the official documentation linked here, and it may not match your model, its version or its firmware. If in doubt, follow the manual and the support of your printer's manufacturer. You decide what you do with your machine, and working on it may affect its warranty.

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