Hi everyone!
im try to repair goldstar msx FC-200
first i was check all voltages and bingo, i have 12V and -12V but 5V is missing.
So i check transformer and this is ok, im suspecting 5V regulator is broken but i dont understand how this regulator work, is a str9005 with 5 pins, according from left to to right:
1 pin output
2 pin is output fine adjustment (is not connected on board)
3 pin is output ON / OFF control
4 pin is input
5 pin is GND
Pin 3 is mystery for me because in datasheet if i good understand, while this pin have 2V or above the regulator is on OFF state and dont give 5V on motherboard. This is stupid because on PSU board this pin is connected via resistor to +12V ! and next is connected via wires to motherboard connector P2. I dont know what motherboard doing with this signal because i cant find this in schematics.
So maybe someone in this forum can help me ?
Thanks a lot!