Schiller AT-2: Paper skews during printing and paper sensor error appears
What happened
On an electrocardiograph, the print paper ran slightly skewed during printing, and the device immediately reported a paper sensor error, stopping the printout.
What was checked
- Fed the paper through manually and watched at which point of the print path it began to skew (as described in the case).
- Checked the print head pressure against the paper and the position of the paper sensor relative to the paper edge.
Cause
As reported in the case, the print head pressed the paper too weakly, so the paper skewed in the print path; the skewed edge then did not pass the paper sensor properly, and the device flagged a paper sensor error.
What was done
As reported, the engineers moved the paper sensor slightly to the side from its original position and installed three springs between the top cover and the printer body, so the print head pressed the paper firmly and evenly. After that the paper fed straight and the sensor error no longer appeared. Replacing the whole printer was discussed as an alternative, but in this case the mechanical adjustment was enough.
Safety
Unplug the device from mains and let it settle before removing covers, and after any work inside the housing run an electrical safety check (protective earth continuity and leakage currents) before the ECG is returned to patient use.
Lesson: A paper sensor error is often mechanical: check paper path, print head pressure and sensor alignment before suspecting the electronics.
Covered in the course: Fault-Finding Method for Medical Equipment →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.