Gage Master GM‑4 is a 2‑axis optical comparator equipped with a microprocessor‑controlled digital readout (DRO) that displays X/Y measurements on a glass screen. Common failure modes for this class of equipment include power supply instability causing the DRO to flicker or lock, loss of communication between the controller and display leading to blank or incorrect readings, and lens or illumination degradation that reduces measurement accuracy. Initial checks should verify proper 12 V/24 V DC input, inspect the main board for burnt components or loose solder joints, and confirm that the microcontroller’s firmware is intact by reviewing any error codes on the screen. If the display remains unresponsive, test the DRO module with a known good power source and examine the I/O connectors for corrosion or mechanical damage.[oss-gpt-20b]