Phenomenon: The printer is working normally above 20 ° C, and there is no reaction or slow (after a few seconds or minutes after a few minutes) at a high temperature of 20 ° C.
Diagnosis and troubleshooting: In terms of working properly at higher temperatures, it is possible to determine whether the power supply load capacity is low or the integrated circuit power consumption is increased due to low temperature, and the CPU detects that a part of the circuit work state is unstable. Can not work normally. Measuring the power output - voltage, current, and ripple, the ripple is large. At this time the printer is basically working. When the power supply output - voltage, power supply, and ripple are measured at low temperatures, the power supply is 5V, 3.3V ripple (600mV / 300mV), linearity. Preliminary diagnosis is low-temperature power consumption, low power load capacity, and the CPU detects the difference between power supply characteristics. 5V power supply filter capacitor C54 (470 U / 6.3V), 3.3V filter capacitor C75 (47 U / 35V) is replaced with C54 (1000U / 6.3V), and the power ripple is normal (200 mV / 8mV) after C75 (220U / 25V). At this time, the printer works fine at high and low temperature. Troubleshooting.
Analysis: This fault is due to the increase in circuit power consumption, the power filter capacitance is small, the load capacity is low, the ripple is increased. The main control circuit cannot be stabilized, and the power supply characteristics after filtering capacitors are improved, and the circuit is stable. ,Troubleshooting.
