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Most ordinary 5mm LEDs are spec'd with a current of 20mA. The current-limiting resistor value for the RED LED is far too low:
1) A red LED is about 1.9V so when the transistor turns on and saturates with a voltage loss of 0.1V then the 270 ohm resistor limits the current to (12V - 1.9V - 0.1V)/270= 37mA which will melt a normal 5mm LED.
2) With 510 ohms the current is 19.6mA.
3) A new bright green or blue LED is about 3.5V. Then the 430 ohm resistors limit the current to 19.5mA.
Little transistors saturate well when their base current is 1/10th the collector current.
The collector current will be 19.5mA so the base current should be at least 1.95mA. (12V - 0.7V)/1.95mA= 5795 ohms. Use 5600 ohms for each base resistor.
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