Diagnose Zebra GK420t printing errors (garbage characters) after a phone line surge. Identify causes & implement safe, external troubleshooting steps.
Confirm if a surge protector is used and its rating.
This isolates the issue to the terminal or printer configuration.
This clarifies the type of connection and potential cable issues.
Data transmission errors manifest as 'garbage characters' when the printer misinterprets the incoming data stream. This can be caused by voltage fluctuations affecting the printer's internal logic, baud rate mismatches (though unlikely after functioning correctly), or corrupted firmware. A surge on the landline connected to the terminal can induce voltage spikes which propagate through connected devices, potentially damaging the printer's serial communication components or causing temporary data corruption.
Electrical surges can damage electronic equipment. Always unplug the printer and terminal before inspecting cables or performing any troubleshooting steps. Do not attempt to open the printer casing or perform any internal repairs. These devices may contain tamper-evident seals; any breach could void the warranty and potentially damage the device. Ensure workspace is dry before handling electronics. Static electricity can damage components, especially during dry winter months. If the printer emits smoke or a burning smell, disconnect it from the power outlet immediately and contact a qualified technician.
To prevent future issues:
1. Use a surge protector: Connect the Zebra GK420t printer and the card terminal to a high-quality surge protector to mitigate the impact of voltage spikes.
2. Implement proper grounding: Ensure all connected devices are properly grounded to minimize voltage potential differences.
3. Regular cable inspection: Periodically inspect all cables for damage and replace them as needed.
4. ESD prevention: During dry months (winter), use anti-static mats and grounding straps to minimize the risk of ESD damage when handling the printer or cables.
A common cause is a baud rate mismatch. While less common than surge damage, double-check the card terminal's serial port speed against the GK420t's settings. Some terminals reset their serial port to a default (e.g., 9600 bps) after a power event. Try the standard self-test print: hold the feed button while powering on. If that produces readable output, the printer hardware is likely functional and the terminal settings need adjustment.