Riso Error A16-525 May 2026

RISO Error A16-525: "Cylinder Home Position Error"

1. What the Error Means

Error A16-525 indicates that the printing cylinder (drum) for a specific color (usually Black, Cyan, Magenta, or Yellow) has failed to return to or find its home position within the expected time frame during operation or initialization.

• "A16" = Cylinder / Drum system issue.
• "525" = Home position sensor timing out or signal missing.

The machine detects the drum’s rotational position using an encoder/sensor. When the drum cannot confirm its reference point (home), printing stops to prevent misregistration or damage. riso error a16-525

3. Verify Print Drum Alignment

Check the print drum for proper alignment and ensure it is not damaged. Consult the machine's manual for instructions on how to check and adjust the drum. RISO Error A16-525: "Cylinder Home Position Error" 1

Step 5: Inspect the Drum Connection

If the error is stubborn, the issue might not be the ink, but the drum unit itself. "A16" = Cylinder / Drum system issue

1. Pull the drum unit out of the machine.
2. Inspect the connector on the left side (or rear) of the drum. Ensure no ink has leaked into the electronic connector ports.
3. Reinstall the drum, ensuring it slides all the way in and locks securely.

---

When to Call a Technician

If you have tried all the steps above—cleaned the contacts, used a brand new genuine ink cartridge, and reseated the drum—and the A16-525 error persists, the issue is likely a hardware failure.

Potential hardware failures associated with this error include:

• Broken Sensor: The optical sensor board inside the machine is physically damaged.
• Main Board Failure: A blown fuse on the main logic board preventing it from reading the ink data.
• Wiring Harness: The ribbon cable connecting the ink station to the main board is pinched or severed.

At this stage, it is most cost-effective to contact your local Riso service technician to replace the faulty sensor or board.

---

Step 1: Visual Inspection & Cleaning (Solves 70% of Cases)

1. Power off the machine and disconnect the main power (for 60 seconds to discharge capacitors).
2. Open the front cover and the side paper transport unit.
3. Locate the PF Register Sensor. (Consult your service manual; it is usually a small green or black PCB with a U-shaped optical slot, located just before the print head carriage).
4. Using a lint-free swab and isopropyl alcohol (99%) , gently clean the inside of the U-shaped sensor slot.
5. Using a can of compressed air, blow out the dust from the surrounding area.
6. While the cover is open, manually rotate the PF rollers and wipe them with a damp cloth to remove glazing.