Dell 780 service manual Diagnostic Lights, Light Pattern, Problem Description Suggested Resolution

4-4-2	Failure to decompress code to shadowed memory
4-4-3	Math-coprocessor test failure
4-4-4	Cache test failure

Diagnostic Lights

To help troubleshoot a problem, your computer has four lights labeled 1, 2, 3, and 4 on the bank panel. When the computer starts normally, the lights flash before turning off. If the computer malfunctions, the sequence of the lights help to identify the problem.

NOTE: After the computer completes POST, all four lights turn off before booting to the operating system.

Light Pattern Problem Description Suggested Resolution

The computer is in a normal off condition or

apossible pre-BIOS failure has occurred.

The diagnostic lights are not lit after the computer successfully boots to the operating system.

A possible processor failure has occurred.

Memory modules are detected, but a memory failure has occurred.

Plug the computer into a working electrical outlet.

If the problem persists, contact Dell.

Reseat the processor (see Processor information for your computer). If the problem persists, contact Dell.

If two or more memory modules are installed, remove the modules, then reinstall one module and restart the computer. If the computer starts normally, continue to install additional memory modules (one at a time) until you have identified a faulty module or reinstalled all modules without error.

If available, install working memory of the same type into your computer.

If the problem persists, contact Dell.

A possible graphics card failure has occurred.

A possible floppy drive or hard drive failure has occurred.

Reseat any installed graphics cards.

If available, install a working graphics card into your computer. If the problem persists, contact Dell .

Reseat all power and data cables.

A possible USB failure	Reinstall all USB devices and check all cable connections.
has occurred.
No memory modules	If two or more memory modules are installed, remove the modules,
are detected.	then reinstall one module and restart the computer. If the computer
	starts normally, continue to install additional memory modules (one at
	a time) until you have identified a faulty module or reinstalled all
	modules without error.
	If available, install working memory of the same type into your
	computer.
	If the problem persists, contact Dell.
Memory modules are	Ensure that no special requirements for memory module/connector
detected, but a	placement exist.
memory configuration	Ensure that the memory you are using is supported by your computer
or compatibility error	(see the "Specifications" section for your computer).
has occurred.	If the problem persists, contact Dell.
A possible expansion	Determine if a conflict exists by removing an expansion card (not a
card failure has	graphics card) and restarting the computer.
occurred.	If the problem persists, reinstall the card you removed, then remove
	a different card and restart the computer.