A16-525 'link' - Riso Error

RISO error A16-525 typically indicates Waiting for the master to be removed from the print drum

. It occurs when the machine's sensors detect a master remains on the drum after a disposal cycle, even if the drum appears empty. Common Causes Sensor Detection Failure:

The master-on-drum sensor is incorrectly detecting light reflections, often due to a dirty or worn-out black light-absorbing strip near the master clamp. Aftermarket Screens:

Generic replacement screens often use a lighter plastic mesh that reflects more light than original metal screens, confusing the sensor. Drum Misalignment:

The drum may not be stopping at the correct "Position-A" angle, causing the sensor to look at reflective metal instead of the black absorber strip. Physical Obstructions:

Small scraps of master material stuck in the clamp or sensor area. Troubleshooting & Fixes Clean the Absorber Strip:

Wipe the black velvet/light-absorbing strip on the drum to remove paper dust or ink buildup. The "Marker/Tape Trick":

If the strip is worn, some users successfully restore it by darkening it with a black permanent marker or applying a small piece of matte black gaffer's tape where the sensor focuses. Reset Procedure: Turn off the machine, hold the Yellow Reset button , and turn it back on to clear persistent false errors. Service Mode Adjustments: Reset test mode to default using Simulation 117 Adjust drum angle compensation using Simulation 959

(typically in the range of -80 to +80) to ensure the sensor aligns perfectly with the absorber strip. Replace Parts: If the strip is severely damaged, you may need a new Light Absorber Strip (Part #023-17004). Are you using an aftermarket screen original RISO drum , and did this error start after a specific master jam? riso error a16-525

What Does RISO Error A16-525 Actually Mean?

To understand A16-525, you need a basic understanding of the RISO ComColor’s paper path. These machines run at speeds up to 150 pages per minute. To achieve that speed, timing is measured in milliseconds.

The "A16" family of errors relates to the PF (Paper Feed) Drive Unit. The sub-code "525" points specifically to a Register Sensor timing failure.

Here is the technical translation: The machine expects the leading edge of the paper to hit a specific optical sensor (the PF Register Sensor) at a precise moment during the feed cycle. When the CPU compares the actual sensor activation time against the calculated standard value, if the deviation exceeds the allowable range (usually ± a few milliseconds), the system throws error A16-525.

What the machine thinks: “I sent the paper. I waited for the sensor to trigger. The sensor did not trigger within the allowed window. Either the paper didn’t arrive, the sensor is lying, or the roller is slipping.”

Step 4: Reset Error via Service Mode

After mechanical fix:

1. In Service Mode → Adjustment → Drum Phase Adjustment.
2. Run automatic cylinder home position detection.
3. If successful, exit service mode and test copy.

Common Causes

1. Dirty Ink Sensors: Over time, ink splatter can cover the optical or contact sensors inside the drum unit or the ink carriage. If the sensor is blocked, it cannot read the ink level.
2. Third-Party or Refilled Cartridges: Riso machines often use chips or specific physical shapes to verify genuine ink. If you are using a refilled cartridge or a third-party brand, the metal contacts may not align perfectly, triggering a "counterfeit" or "empty" error.
3. Dry Ink on the Contact Pins: Inside the printer where the cartridge connects, small metal pins read the chip on the ink tube. If these pins are coated in dried ink, communication fails.
4. A "False" Empty Reading: Sometimes, the internal logic counts the number of prints rather than physically measuring ink. If the counter says the ink is empty but the cartridge is heavy, you are facing a software logic error.
5. Disconnected Drum Unit: If the drum was recently removed and not reinstalled firmly, the power and data connection between the drum and the main body may be loose.

1. The "False Positive" – Contaminated or Misaligned Sensor

This is the most common cause. The PF Register Sensor is an optical device. Over time, paper dust, ink mist, and static-charged debris stick to the sensor lens. If the sensor is dirty, it cannot "see" the paper edge correctly.

• Result: The sensor sends a late (or no) signal, causing the timing mismatch.

When to Call a RISO Certified Technician

You are a competent operator, but some repairs are beyond user level. Call a professional if:

• You have cleaned the sensor and performed the automatic adjustment, but A16-525 returns every 1,000 to 5,000 sheets (Intermittent failure indicates a wiring harness issue).
• You see visible damage to the PF timing belt or gears.
• You do not have access to the RISO Service Mode passcode (varies by region).

Warning: Attempting to disassemble the PF drive unit without the service manual can knock the main timing off permanently, leading to costly head strikes. RISO error A16-525 typically indicates Waiting for the

Conclusion

RISO error A16-525 is intimidating because it halts production instantly. However, it is rarely a catastrophic failure. In 80% of cases, the solution is a simple cleaning of the PF Register Sensor and a basic roller wipe-down.

If you have followed the steps above—clean sensors, check inputs in service mode, and run the standard adjustment—you will likely have your ComColor back up and running within 20 minutes.

Remember: Do not ignore the error by constantly power-cycling the machine. Address the root cause. A clean sensor is a happy sensor, and a happy sensor means a profitable print shop.

For official RISO service manuals and part numbers related to the PF Register Sensor (Part # typically starting with "M" or "K"), contact your regional RISO dealer.

Keywords: RISO error A16-525, RISO ComColor error, PF Register Sensor, paper timing mismatch, RISO A16-525 fix, high-speed inkjet troubleshooting.

If you are seeing Error A16-525 on your Risograph, the machine is essentially stuck "waiting for the master to be removed" from the print cylinder. This usually happens when the sensor detects a master still on the drum, even if you’ve already peeled it off. Why it happens

The machine uses a light sensor to look at a small, non-reflective black velvet strip (the "light absorber strip") near the drum clamp.

If it sees a reflection: It thinks there is a white master covering the strip. If it sees no reflection: It knows the drum is bare. What Does RISO Error A16-525 Actually Mean

If you are getting a "false" error, it’s usually because that black strip has become shiny from ink, is scrunched up, or is a thinner aftermarket version that isn't absorbing enough light. How to fix it

The "Sharpie" Trick: Many users find that coloring the black velvet strip with a black permanent marker helps it absorb light better, clearing the error.

Tape Fix: If the marker doesn't work, apply a small piece of black gaffer’s tape or matte black electrical tape over the strip to ensure zero reflection.

Clean the Sensor: Sometimes ink mist gets on the master-detect sensor itself (usually located in the master disposal unit area). Gently wipe it with a lint-free cloth.

Hardware Check: Inspect the white plastic wheels or gears on the side of the drum clamp; if one is missing or broken, the clamp may not be seating correctly for the sensor to read it.

Reset Procedure: Try holding the yellow Reset button while turning the machine on to force a clear of the current state.

For a visual walkthrough on resolving common drum and master errors like A16-525, this video can help: Riso 3230 A16 525 error resolve Creator Ratikanta YouTube• Mar 30, 2023