Optiplex 780 will not POST

Question

Hey, I'm new and know nothing about computers. I have a Optiplex 780 that is not booting past post. When I turn it on, the power button flashes amber before it changes back to a green permanently. It then tries to boot into post but gives a 1 2 3 error code and 2 quick beeps. The connection to the display then disconnects but the computer stays on completely with no visible problems or errors, except for the 1 2 3 code.

I don't think there is anything wrong with the components as the power supply seems fine. The disk drive seems fine and the computer gives the same error with it disconnected. I have reseated the memory chips and the hard drive. I disconnected and re connected all of the components and checked if any pins were bent and none were. I also checked if the battery was dead or bad and replaced it and reset it and that didn't change anything.

As to the error codes, dells page regarding the 2 beep code refers to it as being an on screen error but I can't see what the error is supposed to tell me because it only loads a quarter of the way through the dell POST screen before disconnecting from the display. There is a myriad of possible reasons for the 1 2 3 code from what I've read and have absolutely no clue on what component is faulty because they all seem to be fine and in working condition. But there is a notable solid orange light on the motherboard which I've read conflicting information about, where some people have said that it means a dead board or that it simply means that the MB is receiving power.

I have no clue how to troubleshoot this thing with such specific circumstances, pls help.

JOcean · Answer

The 1 2 3 code does refer to a dead CMOS battery. You posted that you replaced the battery but did you use a brand new recently purchased battery? And I would also suggest leaving the battery out of the system for 15 minutes before installing the new battery. The CMOS battery does some strange things at times. I recently had a system that would not even power up (the system was only around 2 years old). I suspected the PSU but it checked out OK. After checking the RAM and GPU I pulled the CMOS battery and reset the BIOS. The system powered up like normal after that. It turns out that there may have been a voltage fluctuation in the house when a breaker tripped and that may have been the cause of the CMOS error.

As for the beeps it may be bad RAM. Pull all the RAM modules and see if you get the same beep code when you boot. If so then the MB does not see the RAM when installed or you have bad RAM. Then install only 1 RAM module and try again. If that does not help try the other RAM modules one at a time in similar fashion.

As for the PSU, the only sure way to confirm a PSU issue is to try another known good working PSU.

rotundrodent · Answer

I tried replacing the battery with a brand new one that was recently bought and that didn't do anything. Also, when I take all of the RAM cards out, the computer shows a 1 and 4 error code with a consistent beeping as if in emergency. But when I put even one chip into any slot, the computer goes back to 1 2 3 code.

JOcean · Answer

The next step would be to disconnect everything from the PSU except the MB plugs. Try to power up and if the system does POST then reconnect all the drives, etc. one at a time and attempt to POST after each one is connected. If after connecting one device the system will not POST then you have found the culprit. Of course in the end it is possible that the MB or CPU is the problem. CPUs rarely fail so the MB would be the next consideration.

You can also try a reset with the instructions on the Dell support page here.

rotundrodent · Answer

I tried it and it remains the same. So my guess is maybe the MB or the RAM cards. I have 4 Samsung 2Gb cards and they don't appear to be damaged physically and neither do the slots themselves. Also, other things that confuse me are a battery symbol that appears next to the number code display that appears solid for 10 or so seconds while the computer boots up, and then flashes before turning off completely. And the 4th number on the display appears sometimes while the computer is off.

I have no clue if those last two details I mentioned are normal.

rotundrodent · Answer

Do you have to replace the CMOS battery while the computer is off or completely unplugged? Just to make sure that it wasn't the battery, I got a brand new pack of 2032's and replaced it and it still gave me the 1 2 3 code. Is there any other way to tell whats making that error?

rotundrodent · Answer

Apologies for the gigantic picture. I completely took apart everything out of the case and made sure there were no damages to any parts. But, I did find this peice. The plastic end sits just below the power button and I have no clue where the wired end connects to. Do you know what this part is? Is it possible that its creating the 1 2 3 code? Also, another question is if calling dell support over the phone would be helpful?

I'm absolutely stumped on what this code could possibly be from.

Optiplex Desktops

Optiplex 780 will not POST

Was this post helpful?