CPU damage?

[katz]

Well, a bad habit has finally bit me. I have a desktop in the shop, blew out the dust as I always do without disconnecting the PSU or CPU. I do hold the cpu fan from spinning...

It would seem that the psu has shorted the motherboard, as I have no video output.

Ordered in a replacement board, and still the same issue, no video out. Is it possible that the cpu could be shorted, causing no video?

 

[Altster]

In all of the computers that I have ever blown out I've never blown a CPU (chip). In fact I don't recall ever blowing a motherboard, either. I also hold the cpu fan but I also hold the PSU fan, too!

So I guess the question here is, did the unit work BEFORE you blew it out? Did you power it up to see if it would boot?

 

[katz]

Yes, it did work at the client's home. They had a virus, and they had the pc on so I could see it. Powered it down, brought back to shop, blew out dust, changed CMOS batt., boot to no video.

Ordered a replacement board in, still no video. Supposed to be a working pull, I don't know - and of course, no spare cpu lying around to test further. I've never had this happen before either, guess I'm due for one...

 

[glennd]

Yes, it did work at the client's home. They had a virus, and they had the pc on so I could see it. Powered it down, brought back to shop, blew out dust, changed CMOS batt., boot to no video.

Ordered a replacement board in, still no video. Supposed to be a working pull, I don't know - and of course, no spare cpu lying around to test further. I've never had this happen before either, guess I'm due for one...

silly i know but you do have the monitor plugged in to the right video socket?

 

[katz]

silly i know but you do have the monitor plugged in to the right video socket?

Oh, I wish it were that simple, lol...I've tried every video out on the board...nothing.

 

[glennd]

Oh, I wish it were that simple, lol...I've tried every video out on the board...nothing.

so to be clear, the computer boots up and appears to be otherwise functioning normally except there is no video signal? You're using the onboard video? The situation is identical with two different motherboards? When you initially blew out the dust, the computer was running? and you had video and then as soon as you blew out the dust the video stopped working? or you didn't power it on initially when it arrived at the workshop so you don't know if it would have ever worked at the workshop?
If it is otherwise functioning, does the bios appear on bootup? if yes have you tried booting to linux.

 

[Markverhyden]

Did you verify it was booting when you got back to the shop before blowing out the dust?

 

[Blues]

Did you verify it was booting when you got back to the shop before blowing out the dust?

Yeah I'm in line with this thinking could have been damaged at disconnect or in transit also could be something else funny with your power.

 

[katz]

so to be clear, the computer boots up and appears to be otherwise functioning normally except there is no video signal?
YES
You're using the onboard video?
YES - VGA/DVI/HDMI - all same result
The situation is identical with two different motherboards?
YES
When you initially blew out the dust, the computer was running?
YES
and you had video and then as soon as you blew out the dust the video stopped working?
YES
or you didn't power it on initially when it arrived at the workshop so you don't know if it would have ever worked at the workshop?

It was working at the client's residence. Brought it to the shop, blew out the dust, replaced CMOS batt & that is when I have no video.
PS/2 Mouse lights up, & USB mouse lights up, BUT, PS/2 Keyboard will not light up, nor will USB keyboard light up. Actually, keyboard blinks briefly upon boot, then the led's go out.
Tried a boot disk, looks like the drive is reading it, but again, no video on any ports.

I don't have a video card to test with, unfortunately. I went through all the "junk" in my shop months ago & threw out all the stuff that was collecting dust for ages. Murphy's law, of course, now I need one to test with...

And yes, same situation with the used replacement board.

 

[glennd]

And yes, same situation with the used replacement board.

I know it's possible but what are the chances? I think something has changed between the customer and the workshop. I think I might be putting both motherboards on the bench, outside of the case and see if they can work that way. Maybe with a second PSU.

 

[katz]

I did try a second psu, forgot to mention that. I will try to run it on the bench, that I haven't done yet.. The board is an ASUS B85M-E. I looked through the manual and the board setup is simple, like I've done a million times in the past.

 

[Markverhyden]

Tried different RAM? Did you confirm malware was installed when onsite?

 

[Krynn72]

Tried different RAM?

Surprised it took this long for someone to mention RAM. It would be my first suspect with these circumstances. Power on but no video/sounds is a common symptom of RAM failure.

 

[PcTek9]

Strange things seem to be happening. Well, I've had similiar weird situations before.
1) one time a power button was stuck and the pc rebooted over and over, but you couldn't tell it was stuck.
2) one time i put in a new cmos battery that died on the shelf and shorted out internally, this created a cmos with zero battery power, and an internal battery short. there was no video. :O
3) one time i bent a usb pin plugging in the keyboard and it shorted, the pc wouldnt boot all the way
4) several times usb ports have shorted internally by being plugged into the wrong way by others, and breaking the tab shorting it to the frame of the pc.
5) one time a screw was in the wrong kind of hole and the pc wouldnt boot at all
6) one time i pressed ram in too hard and a solder point on the other side of the board grounded to the metal frame
7) one time the video port itself had come unsoldered from the motherboard and some legs were not connecting, so there would only be video when you moved it the right way ( i had to solder all those little pins back to the board)
see what i mean? it's really hard to diagnose your problem. The guys are right, could be ram, could 2 bad boards, could be a lot of things. Keep posting, we'll try to help.
8) just out of curiosity how flat are the top of the capacitors around the on board video chip? o.0

 

[ohio_grad_06]

Try with no hd connected, no ram, no optical. See if board even squawks at you. Try different video if possible as well. Add parts back one at a time until you isolate where it's failing.

 

[katz]

Good suggestions, everyone. And yep, I've tried pulling RAM, got the beeps from the mobo. Tried different sticks as well, different slots.. I've examined all of the things you mentioned, PcTek9. @ Mark, it is a browser hijack, but it comes back every time you boot, instead of one of those that go away upon reboot.

Capacitors look good on both boards.

We booted it twice onsite, it was running fine otherwise. I carried it out to the car, brought it back to the shop & commenced with the cleaning as I always do. It didn't receive any hard bumps along the way, nothing like that. The only explanation that I can come up with it my initial suspicion, that I cooked the board when spinning the psu.

Ordered a "good/used" board from ebay & still no video - which is not really all that surprising. People sell junk on there, it is not out of the realm of possibility that I received a junk board.

Expensive lesson...if I did indeed short the board. I am going to try to get a video card from another tech today to see if I get can get video that way.

 

[ohio_grad_06]

Edit. Started to mention using a different psu, but realized you already done so.

 

[nlinecomputers]

I have a desktop in the shop, blew out the dust as I always do without disconnecting the PSU or CPU. I do hold the cpu fan from spinning...

You shouldn't do that. It will not help. What you need to do is ground the PC and yourself with a proper grounding strap. It is possible that a static charge will build up with the blowout of the system.

 

[GTP]

This ^^ I've seen computers damaged by over zealous cleaners with air pencils and vacuum cleaners not grounded properly.
Vacuum cleaners are notorious for static build up.

 

[PcTek9]

reflash the bios.
https://superuser.com/questions/29221/is-it-possible-to-recover-a-computer-from-a-failed-bios-update

http://www.hardwaresecrets.com/recovering-dead-motherboards-killed-by-the-cih-virus/

yes i know cih is really old... but just understand the technology or get an idea from this. also i once had a motherboard that you plugged in the big psu ribbon connector to the mb, and then you had to plug in another psu connector slightly more wires, then a 3rd psu power connector which came from psu and had 4 wires in the 3rd one and plugged on the motherboard at some random spot, make sure it didnt come loose. I'm tryin to think of other things that could help you.