General description:
Capacitor leakage and ESR tester 3V... 100V with voltage feedback control. Can be also used for electrolytics reforming. Analog scale readout 0-100 uA / 0-1000 uA full scale. ESR readout 0-25 ohm with zero calibration potentiometer. Function ESR/ leakage can be selected by a DPDT switch.
Function description:
9-volt DC supply voltage is fed to midpoint of a step-up transformer primary through a pass transistor. 4047 provides a constant 100 kHz 50% duty cycle to drive the primary winding halves. After rectification of secondary voltage, a feedback voltage is selected by the rotary switch JP1 (Common pole= pin 12). Feedback voltage is compared against a fixed 1.2V reference in error amplifier IC2, which output drives the pass transistor's base current thus regulating the output.
ESR test voltage is generated by a 74HC14 schmitt trigger oscillator. Test frequency is about 100 kHz. Circuitry consists of an oscillator, AC-coupled transistor amplifier stage, DC clamp, buffer op-amp and a peak detector stage.
Hardware:
4047 astable multivibrator
2x9V/230V step-up transformer
TIP 120 transistors
LF356N op amp error amplifier
uA-meter 0-100 uA
Software: None
Documents:
