The UC3842 needs a startup voltage. A few high-value resistors (two 150kΩ in series) trickle-charge a small capacitor (C6, 47µF/50V) until the chip wakes up. Once awake, the chip sends square waves to the MOSFET’s gate via a small resistor (e.g., 22Ω) and a fast diode.
Who commands this switch? A tiny 8-pin chip: the . In most S-60-12 units, it’s a UC3842 or KA3842 (a current-mode PWM controller). Manish found the chip near the optocoupler. s-60-12 power supply circuit diagram
He connected an old LED strip. It blazed to life. The UC3842 needs a startup voltage
A small variable resistor (VR1, a 1kΩ trimpot) lets you adjust the output from ~10V to 14V. But the real hero is the programmable shunt regulator and an optocoupler (PC817). Who commands this switch
In a cramped, sun-drenched workshop on the edge of the city, old Manish had a rule: “Never throw away a power supply. Its heart may still beat.”