UNSOLVED
Given the 15 + year old system the power supply is bad and the CMOS battery is likely dead.
This system is not worth fixing.
Diagnostic LEDs for the OptiPlex series (Prior to 2005)
LEDPattern StateName StateDescription Suggested Resolution
No Pattern Visible Off System POST complete - LED time-out has occurred - If the LEDs came on and then went off, look at troubleshooting the display and the operating system.
- If the LEDs never came on at any point then look into a power issue.
ABCD RCM BIOS checksum failure - Recovery mode - Reset the BIOS and clear the NVRAM
- If this occurred after windows updates, check your startup wasn't corrupted.
JOcean
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Posted March 9th, 2019 17:00
The service manual does not have a code sequence to match that light configuration. But doing reference on the Net it would appear to be a bad motherboard. You can try disconnecting all of the peripherals, (HDD, SSD, DVD, pull the video card) and see if the system tries to boot. If not pull the RAM and see if you get a series of beeps. If no beeps then that would look even more like the motherboard. Look at the motherboard and see if you have any swollen capacitors on the MB.
Having said all that, the 2400 is pretty ancient as PCs go and I would strongly suggest you bid farewell to a system that has served well long past it's prime and purchase a new, modern and much faster new system.
I am not a Dell employee...I am forum volunteer
Serious work on an E5430 and constantly building and working on an i5-6500 Desktop