hardware issue on new build with old parts

[mjamie]

I took apart an old Dell today to put in some new parts and whatnot.  After tossing the old CPU on a used mobo, (compatible), adding more ram, and putting in a new PSU, I got the computer started, but no video.  There are no POST beeps.  The mobo is getting power and all of the fans are running along with the dvd drive and harddrive.  I have tried the following:

1.  Bench tested both mobo's.
2.  Tried a different compatible CPU in the new mobo.
3.  Tried 2 cases.
4.  Tried each stick of ram in every single slot.
5.  Tried with nothing but CPU, ram, and PSU.
6.  Tried both PSU's and used both for bench testing the mobo's.
7.  Tried the graphics card and then tried onboard.  (The old mobo doesn't have onboard, so I was only able to try the graphics card when testing that mobo).

Did I miss something?  The old computer as a whole seemed to work, but the mobo was acting up and I happened to have a spare 775 in the closet, so I swapped those out.  Now, I cannot get video or POST.  The monitor works on the rig that I moved to create a "test station".  So, everything appears to be working individually, but nothing is working together.  If anyone has any ideas about what I should try next, please please please let me know.  My hair is turning gray over this.

[spikedfox]

Make sure the RAM you added is compatible....

[mjamie]

I did.  I also removed the new ram entirely and tried to boot up with the 2 old sticks.  Both of those were fine, but only 512, so we went ahead and got 1gb and 2gb sticks to put in the empty slots.

[spikedfox]

I did.  I also removed the new ram entirely and tried to boot up with the 2 old sticks.  Both of those were fine, but only 512, so we went ahead and got 1gb and 2gb sticks to put in the empty slots.

Some computers might only run decently or with optimal performances with RAM "twins" (pairs of identical RAM, i.e. same type/capacity). Check the color of the RAM slots to know where to put said pairs . Slots of the same color need matching ram sticks. (if all your slots are the same color, refer to your mother board's manual to know where pairs must go. Though, usually it's first slot of channel A with first slot of channel B, and second slot of channel A with second slot of channel B)

If you haven't already, you might also want to go to crucial.com and scan your system just to make sure you know what type of RAM is compatible.

[mjamie]

Well, I got it to beep.  I picked up a new case today that had a speaker built in.  I figured out that there were 2 bad sticks of ram.  I scrapped those and the beeping stopped...entirely.  It still won't POST.

At this point, I have tried 2 mobo's, 3 CPUs, 3 PSUs, 3 cases, 2 monitors, 2 graphics cards+1 onboard, both VGA and DVI.  I am completely at a loss.  I have no idea why it won't work.

[spikedfox]

But didn't you just say it would work fine with the 2 512Mb sticks?