Electrical – My homemade variable power supply burns potentiometer

pcbpower supply

I have designed my Power supply using this schematic enter image description here
And this is my pcbenter image description here
enter image description here
Everything is connected right but the potintemeter burned twice

Onething i am suspicious of are the parts
C1 1000uf 35v,
C2 0.1uf,
C3 470uf 35v,
C4 10uf 35v but unfortunately I couldn't find it 35v so i bought 10uf 50v which i think is the problem

Is the Pcb okay and if so what is the problem causing the potentiometer to burn ?

Best Answer

If shorting pins 1-2 from the pot give you an output higher than 1.25v then there I see a couple of possibilities.

1) The diode coming across output and input pin of Lm317 is damaged or placed in the wrong direction, check if removing it solves the problem (working without this diode won't damage your circuit unless you apply inductive loads at the output).

2) The IC may have burned and there is no regulation of 1.25v, check the voltage across your 220ohm resistor, it should always be 1.25v.

3) If none of the above solves the problem try arranging the circuit in a protoboard, if it works OK then you might have a broken trace or shortened traces in your pcb.

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