HP EliteDesk 800 Maintenance and Service Guide - HP EliteDesk 800 G1 Tower, HP - Page 216

Power LED flashes Red four times, once every second, followed by a two second pause, and the computer beeps four times. (Beeps stop after fifth iteration but LEDs continue flashing.) Cause Solution Power failure (power supply is overloaded). 1. If equipped with a voltage selector, check that the voltage selector, located on the rear of the power supply (some models), is set to the appropriate voltage. Proper voltage setting depends on your region. 2. Open the access panel and ensure the power supply cable is seated into the connector on the system board. 3. Check if a device is causing the problem by removing ALL attached devices (such as hard drives or optical drives and expansion cards). Power on the system. If the system enters POST, then power off and replace one device at a time and repeat this procedure until failure occurs. Replace the device that is causing the failure. Continue adding devices one at a time to ensure all devices are functioning properly. 4. Replace the power supply. 5. Replace the system board. The incorrect external power supply adapter is being used on the All-in One or USDT. The power supply adapter must be at the correct power rating and use the Smart ID technology before the system will power up. Replace the power supply adapter with the HP-supplied power supply adapter. 204 Chapter 9 Troubleshooting without diagnostics