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Repairing an impulse power supply unit, I connected the probe ground to the ground on the hot side of the converter (to minus of the rectifier capacitor). After that, a message appeared on the computer screen that the usb port is overloaded. On the board, I found that the D400 diode was shorting the + 5 volts to ground. I removed the diode, checked the voltages at C137 = 3.3V, C140 = 1.2V, C430 = 5V, C401 = 5V. Now there is no overload messagebut the indicator LED does not glow and the computer does not find an oscilloscope. I ask for help in repairing the oscilloscope.
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