Hi!
My friend's got stuck with a Winsun WS50–3BAC–01 Chinese 50W power supply from another piece of gear because it had gone bang and rendered a number of small parts indicipherable!
One was a 2W metal film resistor that had burnt up the PCB, R8, which we managed to identify as 4K3 2W from a pic on Aventrepairs' website, but there's a surface mount resistor R7 burnt up underneath, which seemed to measure about 400 ohms over a quarter of what was left and I could make out the first figure '2' but the rest had gone!
Also there's a 500mW zener–diode across the MOSFET current sense resistor (ZD3) burnt black and I can't make out it's marked voltage and it's s/c!!!!
The circuit is UC3842 based, but before anybody tells me to "look in the datasheet!!" I have ALREADY spent four hours this evening searching for another '3842 based circuit example with a zaner directly across the c.s. resistor and I cannot find one!!
Has anyone got or come across one of these Chinese Winsun WS50 psus and can tell me the value of R7 and ZD3's nominal voltage?
Chris Williams
PS!
Why would Winsum add a zener–diode directly across a MOSFET Source Current Sensing Resistor when a search of over two hundred assorted examples using the same '3842 pwm controller totally fails to turn up another PSU with this?
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