Real Time Clock Reset; Recovering The Operating System - Dell Precision 3520 Owner's Manual

When you notice screen abnormalities like flickering, distortion, clarity issues, fuzzy or blurry image, horizontal or vertical lines,
color fade etc., it is always a good practice to isolate the LCD (screen) by running the Built-In Self Test (BIST).
How to invoke LCD BIST Test
1. Power off the Dell laptop.
2. Disconnect any peripherals that are connected to the laptop. Connect only the AC adapter (charger) to the laptop.
3. Ensure that the LCD (screen) is clean (no dust particles on the surface of the screen).
4. Press and hold D key and Power on the laptop to enter LCD built-in self test (BIST) mode. Continue to hold the D key, until
the system boots up.
5. The screen will display solid colors and change colors on the entire screen to white, black, red, green, and blue twice.
6. Then it will display the colors white, black and red.
7. Carefully inspect the screen for abnormalities (any lines, fuzzy color or distortion on the screen).
8. At the end of the last solid color (red), the system will shut down.
NOTE: Dell SupportAssist Pre-boot diagnostics upon launch, initiates an LCD BIST first, expecting a user intervention
confirm functionality of the LCD.

Real Time Clock reset

The Real Time Clock (RTC) reset function allows you to recover your Dell system from No POST/No Boot/No Power
situations. To initiate the RTC reset on the system make sure system is in a power-off state and is connected to power source .
Press and hold the power button for 25 seconds and then release the power button. Go to
NOTE: If AC power is disconnected from the system during the process or the power button is held longer than 40
seconds, the RTC reset process is aborted.
The RTC reset will reset the BIOS to Defaults, un-provision Intel vPro and reset the system date and time. The following items
are unaffected by the RTC reset:
● Service Tag
● Asset Tag
● Ownership Tag
● Admin Password
● System Password
● HDD Password
● TPM on and Active
● Key Databases
● System Logs
The following items may or may not reset based on your custom BIOS setting selections:
● The Boot List
● Enable Legacy OROMs
● Secure Boot Enable
● Allow BIOS Downgrade

Recovering the operating system

When your computer is unable to boot to the operating system even after repeated attempts, it automatically starts Dell
SupportAssist OS Recovery.
Dell SupportAssist OS Recovery is a standalone tool that is preinstalled in all Dell computers installed with Windows operating
system. It consists of tools to diagnose and troubleshoot issues that may occur before your computer boots to the operating
system. It enables you to diagnose hardware issues, repair your computer, back up your files, or restore your computer to its
factory state.
You can also download it from the Dell Support website to troubleshoot and fix your computer when it fails to boot into their
primary operating system due to software or hardware failures.
For more information about the Dell SupportAssist OS Recovery, see Dell SupportAssist OS Recovery User's Guide at
www.dell.com/serviceabilitytools. Click SupportAssist and then, click SupportAssist OS Recovery.
how to reset real time clock.
Troubleshooting 99