System won't turn on... even after new parts

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
*PLEASE READ THE RESPONSES IN THIS POST SO YOU DON'T POST DUPLICATE SUGGESTIONS, THANKS! Very Happy*

I am working on a computer I built a little over a year ago for a customer. About a week ago the owner says it just would not turn on at all. He wanted it fixed, and for some new upgrades to be installed. I looked at it and it seemed like the PSU was dead, but even when I tried it with a tester PSU it still wouldn't come on. I unplugged ALL peripherals, and removed and re-seated the video, sound, and RAM. After that didn't work I tried unplugging every thing including the optical drives and HDD... still wouldn't turn on with just CPU and RAM installed. (usually it will at least turn on with just that even if it gives you error beeps) I checked to see if anything was grounding the mobo or anything else, there are no blown capacitors, I reset the BIOS by pulling the CMOS battery, still nothing. We've already ruled out the power switch by pulling the case leads and using a flat head screw driver to make contact on the power jumpers, and we replaced the power cord from the wall the to PSU. (yes, there was power to the wall socket, it was plugged in, and the power switch on the PSU was ON Wink lol) I also pulled everything out of the case and assembled it thinking maybe the case was somehow grounding it. When you turn off the system you hear that faint kinda pitched power down noise that you hear sometimes when you pull the power cord and press the power button to drain residual charge from the board... so I know it's getting power. (if your a tech you'll know what I'm talking about) After all this I ordered a new PSU, motherboard, video card, and CPU as upgrades/replacements. (I thought that the mobo or CPU was dead) Now, even with a new CPU, new Mobo, new PSU, and new video card... IT STILL WON'T POWER ON! Oh, and then I even repeated all of the above steps with the new parts. ANY SUGGESTIONS? I'm at my wit's end!
 

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
Well I could take each of the new components and try to plug them one at a time into another system to test them... but for one they are new, and two the "old" parts wouldn't power on either. It just doesn't make sense... I must be missing something. I have checked and re-checked, and even had another tech come check my work to make sure I have everything plugged in correctly (both the power and data cables for everything). There's gotta be something I'm missing... probably something that should be obvious but I'm just not seeing it. THE SYSTEM WON'T POWER ON AT ALL... no lights, no beeps, no NADA.
 

samir_nayanajaad

Distinguished
Feb 22, 2006
331
0
18,780
ok the only thing that is in with the "new" parts that is "old" is the ram. I dont know why bad ram would stop the pc from powering on(then giving you some beeps), but maybe.

the next thing I thought of is a long long long shot. I assume you are using the "old" case from the customer right? Well if you are maybe the power switch on the case has for one reason or another decoded not to function. Try a new switch or just cut the wires, strip them, and twist them together. I would try to find a new switch and test it cuz I dont think the customer will like it if he sees that some wiers have been cut then taped back together if it is not the problem.
 

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
I've tried different wall plugs, changed the power cord, tried with and without my Belkin UPS, I got a new working power supply, and new motherboard, and new CPU... what else in that chain could be causing this problem? By power lead I assume you mean the one on the PSU... but this is a new PSU and I know it's getting power because I can hear it power down/discharge when I unplug it.
 

mkaibear

Distinguished
Sep 5, 2006
678
0
18,990
I mean the one from the wall to the PSU.

Got a spare case to fit it into so you can see if it's the switch on the case which has gone?

I'd suggest building a *completely* new system, make sure it powers up, then swap parts into it till it stops working.
 

samir_nayanajaad

Distinguished
Feb 22, 2006
331
0
18,780
oh just thought of using the reset switch on case for the power switch. you will have to hold it for power but its pretty easy to flip flop the power and reset headers on the mobo. a quick test anyway
 

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
Yeah I thought about the RAM... you're right it shouldn't stop the system from powering on. I even tried it without the RAM plugged in though. Normally that would just give error beeps or not POST.. but it should at least power on. (the fans don't even jump) I'll have to test that when I get back home. As for the power switch, I thought of that too. I just pulled all the case's wires from the mobo and used a flat head screw driver to make contact between the two power jumpers... still no go. (that always works) So that pretty much rules out the power switch. I even pulled ALL the components out of the case and set them on cardboard on a table (like how Tom's does sometimes to test new stuff really quick) to see if something about the case was grounding it... nothing. I've never seen this in 8 years of working on PC's where even new components didn't solve the problem. WEIRD!
 

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
I mean the one from the wall to the PSU.

Got a spare case to fit it into so you can see if it's the switch on the case which has gone?

I'd suggest building a *completely* new system, make sure it powers up, then swap parts into it till it stops working.

yeah I swapped the power cord from the wall to the PSU... and in my above post I pretty much ruled out the case by taking it out of the equation... and I did basically build a new system by using a brand new PSU, brand new motherboard, and brand new CPU not installed in the case with nothing else but the RAM installed (even tried it without the RAM) Does any of this make sense? Do I just have bad luck or what? LOL
 

samir_nayanajaad

Distinguished
Feb 22, 2006
331
0
18,780
The next thing I can think of thats still a long shot, maybe the new psu is shotty as well was the old one. got a multimeater? test it if you do.
very doubtfull but hell I dont know what else to tell you that you havent tried.

also test your wall outlet voltage, and that little switch at the back of the psu that tells it if you use 220 or 110 (or is it 115 I cant remember)
 

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
Thanks guys... I'll check out all that when I get home. :) I've got 2 other systems with good parts in them that I can try swapping parts in and out of... something's gotta work!
 

sony3127

Distinguished
Jul 8, 2006
150
0
18,680
Yeah I've gotten DOA new parts before. Just my luck one probably is. I'm going to test each of the new parts in a working PC to make sure they're not DOA. Oh, and we've already ruled out the power switch by pulling the case leads and using a flat head screw driver to make contact on the power jumpers... still no go.