The three feet are 16VLy respectively.

**Mitsubishi SRK325HENF-W Air Conditioner: Both remote control and manual operation failed to start the unit, and the panel indicator showed no display.**

### Repair Process:

1. First, check IC3 (LM7812). The voltages at pins 1 and 3 were 16V and 12V respectively, both normal.

2. Then, measure IC4 (L78LR05D), and find that the voltages at pins 1, 4, and 5 are all 0V.

3. After checking, it was found that resistor R1 had an open circuit. After replacing R1, the voltages at pins 1 and 5 of L78LR05D returned to normal, but the voltage at pin 4 was still abnormal, with no sudden change in voltage.

4. Analyzing the circuit, it was determined that pin 4 of this integrated circuit provides a reset signal to the CPU's RESET terminal. During each power-on initialization, this pin provides a low-level signal to the CPU's reset terminal until the CPU's power supply establishes a stable 5V voltage, after which pin 4 rises to 5V. Based on this, it can be inferred that the circuit has lost its reset function.

5. After replacing the L78LR05D integrated circuit, using the remote control to turn on the air conditioner still had no effect. However, at this point, manual startup was possible, and the yellow and green lights on the panel lit up. After a delay of 3 minutes, the compressor also started working.

From the above situation, since manual startup is possible, it indicates that the basic operating conditions for the CPU have been established. The main issue lies in the remote transmission and reception circuit part.

Further examination revealed that the potentials of D1, D2, and D3 in the receiver K532D were all normal. When pressing the remote control, D2 outputs a DC pulse voltage greater than 3V. Measuring IC1 (D78C12ACW), the voltages at pins 19 and 20 (PC2, INT2 terminals) were greater than 4.5V, indicating that the remote control reception signal had been sent to the remote control signal input terminal of IC1. Based on this, it was concluded that the fault occurred inside IC1. Since there are two reception ports inside IC1, the 20th pin was disconnected, and the signal was rerouted to the 26th pin, with the 26th pin connected to a high level through a resistor.

After rewiring and powering on for testing, both remote control and manual startup were successful. The fault was resolved.

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**Source:** http://blog.sina.com.cn/sanlingkt