Blank screen when turning on computer. Bad MBCPU?

Heres the outline:

The computers are 3 years old. All of them are Dell Precision 360 desktops. Fresh install from Dell CD-ROM. The first one was working just fine for a while. Then it started going to this blank screen. No HD access light, no response to keyboard/mouse, no video signal, power led/fans still running. Restarted the computer and it worked fine. After a week or so (and a few more blank screens) restarting the computer no longer worked. It would boot to this blank screen. No video signal.

Here's what I've tried:

First I wanted to check and make sure that the parts in the computer were working properly. Tried replacing the video card. no go... Pulled the RAM to see if I would get an error code and didn't get any beeps at all. My first guess was it must be the PSU. So I bought a new one. I couldn't install it properly thanks to Dells POS "custom fabricated" cases. Had to run the computer with the case open. Same thing when I press the power button: no video signal, no post beep(s), power LED turns on and fans are running.

I'm guessing it's either the MB or the CPU.

Well heres the kicker. There are some more of these Dells around we got 4~5 of them. One of them has just started showing the same symptoms as the original computer. Occasionally loses video signal with the power light still on and fans running. We're guessing it will end up the same way as the first one, but it hasn't yet. Since this computer is exactly the same as the last one (except the video card) I decided to run the dell diagnostics for the system board and CPU and more for the heck of it. All tests passed with no errors.

Has anyone had a similar problem?

Cheers

Nails

 

I believe you should get a beep even with a bad processor. I would suspect the motherboard.

 

Thanks for the quick reply Whiskeyman. Was thinking the same thing. Should get some kind of post beep even with a bad CPU.

Any idea what could cause this to happen to a motherboard. Especially in multiple computers? Or maybe it was a problem that was already present. Hrrm. I'll post again after I swap out the motherboard.

Cheers,

Nails.

 

Maybe a batch of motherboards that were manufactured when that run of bad caps came out?

 

Dell's have a limited (cut down) BIOS. They "lose the plot" if something a little out of the ordinary happens.

I suggest replacing the CMOS battery, pulling out and reseating the connections.

We had a spate of strange happenings to our Dell workstations where I work. I spoke with our contract electrican. We may have been getting "dirty" power from the power company, for some reason all the problems are completely gone now. Electrical supply for a business working with it's own substation can have a "balance" to reduce the cost of supply. Talk to someone at the power supply company about the "multiple occurances ".
Try taking the machine home with you and working on it there.

Matt

 

Thanks for the thought mattman. The computers are in different units, only about 500 meters apart. If it does have something to do with the power company my house would be under that same influence.

Dell was called and after doing everything I already did once they agreed that it's the motherboard and a new one has been ordered for one of the computers so we'll find a bit more out after that is replaced. Dell also offered to take the computer back if this does not work which is kind of them.

One concern I have is similar to mattmans, but a little different. Could the power supplies be too small for these systems? They have 3GHz processors, CD-ROM drive, 1 IDE HDD, 2 Sticks of DDR, decent graphics card, but only a 250W power supply... I'm kind of concerned that I'll install this new motherboard only to have to computer die again in the exact same way in a few weeks. Then again these computers did work for 3 years at another location so the power supplies must have lasted this long.

The other computer which is having symptoms hasn't died yet. It has lost it's video signal about 5 times now to my knowledge. None of the other work stations that have been installed have had any problems, to my knowledge, yet.

I'll post again when there is more information to offer.

Cheers,

Nails

 

Sorry, I meant to reply the other day.

At the basic Dell configuration the PSU will probably cope, even though it may be under heavy load (see the link below). I would not even consider adding an extra drive though.
Here is a power supply calculator:
http://www.journeysystems.com/power_supply_calculator.php

 

In my recent experiments exchanging CPU's the dead one gave no beeps from the mobo.
hawk22