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May I know the value of the burnt resistor?Thanks!!

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Externet

Externet

Joined Nov 29, 2005
2,681
Not exactly. As a guess, it may be in the vicinity of 47 Ohms, and probably blew up because the power transistor is very shorted base to collector, and that happened either by over current in the secondary or the switching stopped in conduction state.
Try to find another power supply to read its value and replace after fixing the cause.
 
Ron H

Ron H

Joined Apr 14, 2005
7,063
Externet said:
Not exactly. As a guess, it may be in the vicinity of 47 Ohms, and probably blew up because the power transistor is very shorted base to collector, and that happened either by over current in the secondary or the switching stopped in conduction state.
Try to find another power supply to read its value and replace after fixing the cause.
Click to expand...
The 240 ohm resistor will limit the current to less than 10mA. With 47 ohms, Vbe would be less than 0.5V, so the BD140 would never turn on.
I would try a resistor in the range of 470 ohms to 1k.
 
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