Where is thee Onda B250's power pins, anyone?
three? power pins?
The power on button location?
The two pins that I can connect a power button. The only button I can see the BIOS reset button which restarts the CPU but also resets the BIOS to default.
The Onda D1800 is configured from the factory to boot automatically when power is applied; perhaps the B250 is configured similarly. Did you try doing that?
Otherwise, the pin header for the usual power switch, power LED, reset switch, HDD LED should be located in the corner near the ATX 24 pin connector.