Agfa Drystar 5300: overheat error on a cold power supply
What happened
Right at power-up, on a completely cold power supply, the printer reported an overheat error.
What was checked
- Located the temperature sensor inside the power supply unit and traced its circuit
- Checked what the error actually refers to and confirmed the overheat flag came from the power supply, not from the thermal print head
Cause
The overheat protection is built on a thermal fuse that feeds an optocoupler through a current-limiting resistor. In this case the engineers found that the track running to the thermal fuse had burnt open in an inner layer of the power-supply PCB, so the protection circuit reported an overheat even on a cold unit.
What was done
The engineers restored the burnt track with a fly-wire on the board surface. The protection circuit worked normally again, the overheat error no longer appeared, and the printer was returned to service.
Safety
Disconnect the printer from the mains and let the power-supply capacitors discharge before probing or soldering on the PSU board, and only return the unit to use after electrical safety checks.
Lesson: An overheat alarm on a stone-cold unit points to the protection circuit itself — check the sensor, its wiring and the board tracks before blaming the heated components.
Covered in the course: Medical Imagers and Film Printers — Level 2: Fault-Finding →
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.