: Wipe the small black velvet strip (usually near the clamp) with a dry cloth to remove paper dust.

: If using an aftermarket screen, use a black permanent marker (Sharpie) to darken the entire black strip and the area around it to ensure no light reflects back to the sensor.

If the error persists on a clean drum, it is likely an optical detection issue.

: Non-original "generic" silkscreens often use white plastic mesh. The sensor's light reflects off this mesh, tricking the machine into thinking a master is still attached.

: If the drum's "Position-A" is slightly off, the sensor may look at the wrong part of the drum (like the metal surface) instead of the black absorber strip. Troubleshooting and Fixes 1. Immediate Physical Check

The is a common "service call" code on Risograph digital duplicators, typically indicating that the machine is awaiting master removal from the print cylinder . While it primarily signals that a used master is still attached to the drum when the machine expects it to be gone, it often appears as a "false" error even when no master is present. Common Causes of Error A16-525