Hello there
I have found two things which will help you.
A Technical Guide to the Optiplex 790 which will download from here:
http://www.dell.com/downloads/global/products/optix/en/optiplex-790-tech-guide.pdf
It is in pdf format and can be saved to your computer for future reference.
Also I found a Service Manual here:
Dell OptiPlex 990 Desktop Service Manual Page 76
If you click on the green download button at the top of the page then you will taken to a page where you enter 3 letters that are given to you and you can then opt to download it or view in your browser. In both cases it can be saved to your computer.
The latter has a good section on beep codes, and light codes on page 73 ( Chap 20) and following.
It gives your 2-3-4 as a possible USB failure, so try booting with no USB items attached - printer, flash drive, scanner, external drive etc.
It gives your 1-2 code as an expansion card failure and gives various means of checking.
Hope this is helpful, if so would you please register that with Fixya
Cheers
790MT, I have one, and runs any GPU card.
why on earth post 4 times,
A VERY OLD pc
1:DELL.COM, THE MANUAL SAYS, BAD DDR MEMORY.
2:This PC has very old RTC coin cell battery
9 year old battery (if) is 3 years past the 5-7 year life span, below 2.9vc is bad. replace it first. The BIOS goes nuts if this fails and BIOS can lie to you with a bad coin cell.
the manual on your PC covers this.
yes reSeat DDR. sure. (ram bank)
better is run DDR sticks 1 at a time to see if one is bad. easy no?
URL:https://www.dell.com/support/home/en-us/...
RTM.
reseat ram. DDR memory bank.
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