First post, by megatron-uk
I am in the process of integrating a Pico PSU with my tiny 486 SBC build.
Everything is working except the operation of a power LED.
I have a switch connected to PS_ON and COM (specifically ATX pins 14 and 15), and this works to turn the system on and off. When the switch is closed the SBC boots, its buzzer works, the system boots, the hdd led flashes... everything works normally.
But...
I have also wired a LED between +3.3v DC and COM (on ATX pins 2 and 3) as a power-on indicator. This is with an appropriate resistor in line with the specs of the led (it was either 47 or 56Ohm, I forget which). The odd thing is that when PS_ON is shorted, and the system is on, the LED is unlit. With PS_ON open, the LED is lit. This is... not exactly what I thought should happen.
I was under the assumption that +5VSB (ATX pin 9) was the only other pin that had voltage while the system was off... so why is the LED connected between 2 and 3 live with the power off?
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