Here is the front panel motherboard pinout. This is a view of the motherboard. Pin 6 is the key, a missing pin, which will help to identify the connector orientation.
The Z420, Z620, and Z820 all have the same front panel connector pinout.
- Pins 2 and 4 are for the power LED. HP systems have back-to-back LEDs connected across these pins. A white LED is lit in normal operation and red (and blinks error codes) when there are errors.
- Connecting a momentary power switch between pins 7 and 8 will turn the computer on and off.
- The Ambient Sensor pins are for a thermal sensor in the front panel cable. If this is sensor is not installed, the system fans will probably ramp to full speed and be very noisy.
- Speaker Out is for the internal speaker.