PowerEdge 1950 Has NO VIDEO

Hello,

Unfortunately, my server seems impossible to configure because no VGA output do not work! Neither on the front face or the rear face.

I tried unplugging multiple devices. But my screen still does not work, it remains in standby!

symptoms:
- The server starts,
- It makes noise,
- There is no error displayed on the LCD (except Chassis intrusion if open).
- Keyboard and mouse do not light

I've also redone all thermal units seals on coolers and cleaned the contacts on the connectors with a special cleaner for electronic contacts.

Despite all this, my screen does not turn on and the mouse either!
The same screen works perfectly on another machine!

Thank you for your help because I do not know what to do ...