: Dell BIOS often checks for a proprietary ground loop. If your system reports a "Power Button Cable Failure" at POST, you may need to bridge Pin 8 and Pin 10 to simulate the presence of the original Dell cable.
These are the most critical pins. Shorting them will boot the system. Because it's a momentary switch, orientation (polarity) does not matter. dell mih61r mb front panel pinout
| Pin | Signal (Row 1 - closest to edge) | Pin | Signal (Row 2 - inner row) | | :-- | :--- | :-- | :--- | | 1 | | 2 | Power SW + | | 3 | HDD LED - | 4 | Power SW - | | 5 | Reserved / GND | 6 | Unused (No Pin) | | 7 | Reset SW + | 8 | Power LED + | | 9 | Reset SW - | 10 | Power LED - | : Dell BIOS often checks for a proprietary ground loop
The header is typically arranged in two rows. Below is the mapped layout based on community consensus for these boards: Description Hard Drive Activity Light (Positive) Power LED + Power Status Light (Positive) Hard Drive Activity Light (Negative) Power LED - Power Status Light (Negative) Power Switch Connection to Power Button Power Switch Connection to Power Button (Return/Ground) Unused / Reserved Shorting them will boot the system
Are you , or just troubleshooting a power-on issue? Dell OptiPlex 390 Desktop Owner's Manual