Pc fails to boot up, but only sometimes.

[Fluffyunii]

Hi everyone,

 

First of all I'll get into the system itself. Its a dinosaur love project for myself, which is probably weird to you guys when you find out it's a beefed up (ish) Dell optiplex 745 from 2006. The system was a gift from a special person in my life so prefer to not let it die.

 

The issue: it will only work roughly half of the time I start it up. It will fail to post, doing nothing but puffing out air from the jet engine fan on the front and flash boot codes, 1 - 2 - 3, 1, 1 - 2 - 3.

 

I've replaced hard drive, memory, changed CPU to original and then to a xeon and tried to boot without graphic card installed all to no avail. Everything in bios is normal and showing and all devices work properly (except that the CPU isn't tested compatible) when it does boot, however if the monitor turns off the pc will crash to black screen and will need to be restarted, at that point it won't work.

 

I've gone through everything I can think of, hours and hours of forum trawling and Google searches. Pages and pages of notes, diagnostics etc and never found the issue. Psu tests all show normal and no popped caps anywhere in the pc, no shorts on the board that I could find.

 

Leads me to believe motherboard somehow but I don't know what could possibly cause it to be so temperamental.

 

Any help greatly appreciated. 

Thanks!

 

 

 

[Praesi]

Since you changed almost everything but the Mainboard i guess its the reason why. One of the BUS´s maybe damaged. Impossible to find out without extreme expense.