A diagnostic guide for technicians with the references listed below. Measure with the right tools and follow safe working procedures.
A Redmi 13C LCD that does not display an image does not necessarily mean the panel must be replaced immediately. If the device still shows signs of power, such as vibrations or sounds, the inspection should begin with the panel’s power supply and control lines. According to guidance from MJPRO Indonesia, the Input, Output, Command, Protection, or IOPP, sequence helps technicians trace the problem step by step instead of simply guessing.
Start with the reference points
On the Redmi 13C board, the inspection refers to the TS (Troubleshoot) panel → LCD/Touchscreen Core Test Points, Ref J3001. This section contains 13 test points grouped by function, but the initial diagnosis can focus on the four points most closely related to an inactive LCD.
Before taking measurements, set the multimeter as needed and ensure that the probes do not bridge two adjacent points. Careful measurement is essential to prevent the inspection from causing a new short circuit on the board.
Check the three Input lines
The first point is VIO18_PMU 1.8V. This line is the IO rail for the panel and touch controller, so its presence should be confirmed first. Compare the measurement with this value before continuing to the next section.
Next, measure LCM_AVDD +4.5–6V and LCM_AVEE −4.5–−6V. Both are checked as part of the panel’s power supply. The negative value on LCM_AVEE does not mean the probes are reversed; it is the normal value specified in the guidance. Record each measurement so that any line with an abnormal value can be clearly identified.
Make sure the reset Command is present
If VIO18_PMU, LCM_AVDD, and LCM_AVEE are within specification, continue by checking the panel reset signal. This point indicates whether the panel is receiving the command to start operating. The guidance does not specify a particular value for this signal in this explanation, so technicians do not need to establish their own numerical reference.
This sequence is important because normal power supplies do not automatically confirm that the panel has received the command to turn on. By checking the panel reset signal after the Input lines, technicians can distinguish a suspected power supply fault from a panel control problem.
Interpret the results using the IOPP sequence
The diagnostic sequence is Input (VIO18, AVDD, AVEE) → Output (the result delivered to the panel) → Command (reset) → Protection (if the circuit protects itself). If any Input is outside specification, focus the investigation on that line. If all power supplies are present but the LCD remains off, turn attention to the panel reset signal and a possible protection condition.
The IOPP method makes the inspection more focused: measure the sources required by the panel, examine the output to the panel, confirm that the command is present, and then consider Protection. This ensures that the decision to replace the LCD is made only after the power supply and control lines have been checked, rather than as the first step.
