The most common cause is a master that did not eject properly and is still partially stuck to the drum.
Understanding and Fixing Riso Error A16-525: A Complete Troubleshooting Guide
: The bare black velvet strip is exposed. When the sensor emits light, the black fabric absorbs it completely. No light reflects back. The machine registers: "Drum is empty; safe to load a new master."
If cleaning fails, more advanced solutions are required. Replacing the feed tires and separation pad is a standard, low-cost procedure that restores mechanical reliability. In cases where the error occurs only when printing on heavy stock (e.g., cardstock), adjusting the "paper thickness" dial or lever to a heavier setting changes the pressure between the feed roller and separation pad, allowing thicker media to pass. For persistent sensor errors after cleaning, a sensor test mode exists within the Riso’s service menu. Entering this mode (often via a specific key sequence) allows the user to wave a piece of paper in front of sensor 525 while the machine is idle; if the display does not change state, the sensor is electrically dead and requires replacement by a certified technician. Attempting to bypass or ignore the A16-525 code—by repeatedly pressing the reset button—is counterproductive. It will only lead to crumpled masters, ink on the pressure roller, or costly damage to the drum’s mesh. riso error a16-525
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.
Tell you for your model (e.g., EZ220, RZ200, MZ770). Explain how to enter Test Mode to check for faulty sensors. Suggest where to buy replacement parts .
: If the drum isn't stopping at the exact right angle, the sensor may be looking at the metal body instead of the velvet strip. In Test Mode, Simulation 941 (Position-A adjustment) or Simulation 942 can be used to tweak the drum angle. The most common cause is a master that
After mechanical fix:
Before opening any panels, try a simple power cycle:
: 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. No light reflects back
Follow these diagnostic steps in sequence to resolve the issue. Step 1: Perform a Physical Master Clearance
She ran a cleaning cycle and set the lighter, fresher paper back in. The machine coughed, spat, and then sighed into life. The run restarted, pages marching out in neat columns. For the rest of the afternoon, whenever the Risograph hiccupped, Marta would glance at its feeder as if watching a sleeping animal. Sometimes she’d find a scrap — a receipt, a dried bus ticket, a grocery coupon with a child's handwriting — and she would tuck it into a small cardboard box on her workbench.
According to PrintCopy.info , the A16 code indicates a "Waiting for the master to be removed from the drum" state.
The error on a Riso duplicator indicates a "Master Disposal Jam" or a failure in the master disposal compression mechanism. Essentially, the machine tried to discard a used master into the disposal box, but it got stuck or the compression plate failed to move correctly. Quick Fixes to Try First
