M5237L voltage regulator

[Richards5947]

Hi, I'm a Newbie to the forum. I spent my working life on computers of various sizes and for a hobby fix digital pianos.
One uses the above regulator to give 3.3 volts to feed memory chips, the output was 5.5 from the PNP driven transistor. So I assumed that was my problem. I reproduced the circuit on veroboard and still get the 5v on the output and cannot understand how the 5237L is regulating the output. Obviously I am not understanding how the 5237 is controlling the 2SA1451 transistor. I have attached the circuit from the keyboard schematics, hope its legible. Can someone explain how the circuit works and why I'm getting 5 volts instead of 3.3 please?

 

[ronsimpson]

There is a good chance the transistor is shorted. (TR1) Ohm meter it out. In your circuit, check if the M5237 is backwards.
Pin 3 measures the voltage (1.26V). If the voltage is too low it pulls current (pin-1) that turns on the transistor. If the voltage is too high it decreases the current to turn off the transistors. The two resistors divide the 3.3V down to 1.26V. The 220 ohm Base-Emitter resistor must be there.

 

[Richards5947]

Many thanks for a clear and concise explanation, very helpful. Thanks again

 

[Richards5947]

It helps if the diagram Yamaha have of the transistor has the pins numbered correctly!!!!!!!!!!!!!!!!!