Fans twitch but the computer wont start

[malagash]

I am working on someone's unit which suffered the humiliation of being "cleaned out" with several blasts from an air compressor. Seems the unit was dusty after completing kitchen renovations... :0
When I push the power button the CPU fan and cooling fan twitch but the computer wont start. It never gets to POST.
I have disconnected all cards and hardware but the problem is the same.
I removed the battery, reinserted it but no joy. Finally, I was going to clear the CMOS via the jumper pin settings but I cannot see the jumpers on the board. I have the schematic and I see a reference to the CLRTC1 on the board but only see two solder points and no jumper/pins.
Any ideas on where I should look now?
TIA

 

[BadBigBen]

PSU...

the symptoms indicated point toward a bad PSU, either the 12v rail or the 5v rail does not produce enough power for the mobo to start up...

alternatively it could also be the HS FAN of the CPU, ergo when this fan does not move, the mobo will not start...

but my bet is on the PSU...

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

 

[malagash]

Thanks BBB.
The fan spins freely however that doens't mean it is working....

We are about to try another PSU to see but I think we have a fan that we can try as well.

 

[rcp032]

Some times something can be tripped in the PSU which prevents it from powering on.

If this is the case, you can completely unplug your PSU from the wall (surge protector i hope) for 30 seconds or 2 minutes.

This will reset the PSU and it will then work pleasently.

 

[malagash]

Thanks rcp but it has been in and out of the wall on repeated occasions for hours at a time

 

[stduc]

My money is on there being a problem with the CPU.

Step 1 - remove power cord - flip switch and press the power button for a few seconds. Re-attach power and see what happens.

If step 1 fails - remove all cards, disk drives etc (just remove the power to the drives) + remove RAM.

re-apply step 1. If PC doesn't beep like mad on power up - then remove heatsink - clean off all the gunge and using a new heat pad or fresh grease re-assemble.

BTW I just used something called CPU & Heatsink cleaner to fix a similar problem - worked a treat to remove the old heatpad - I then finished off with isopropyl alcohol to remove all traces of the cleaner. (Much easier than isopropyl alone)

 

[dementg]

When a power supply gets overloaded, it will behave the way you describe. It will start to power up for a fraction of a second, then trip the overload protection and shut off. Subsequent attempts to turn the machine on will have no effect, until you reset the PSU. This problem can occur when a motherboard is short-circuited somewhere.

It might be a good idea to simplify the situation. You could try taking the board out of the case, and put it on a piece of cardboard on your desk. That eliminates the chance of a short against the case. Hook up the PSU, a fan, and nothing else. Use a screwdriver or preferably a wire-stripped pin connector to short the "power on" pins on the motherboard. If it still twitches but won't power on the PSU, then at least you know it's either the board or the PSU. At that point I'd try another PSU, preferably a more powerful one. I've just recently had a PSU begin refusing to start on a particular board, but that board and PSU still work with different mates.

Check carefully that the board doesn't have some debris causing a short somewhere. If you have a multimeter, that might help find if there's a short across any of the mosfets. But I doubt that there's any actual component damage, because the timing would be awfully coincidental. I'm guessing there could be some debris though.

 

[SkipCox]

My money is also on the power supply...good call for the folks who jumped thatta way.

CPU heat problems will show up later and the spin and die is a classic psu problem in an otherwise solid machine.

Skip

http://skipcox.net

 

[malagash]

Tried another HS fan and the problem was still there.

Finally was able to insert another ps and all is fine. The original one probably died as a result of the husband being a little tooooo agressive with an "air compressor" (not the can of dust off). Seems he likes to watch the dust fly...???

Likes to watch his money fly and all!

Thanks all for your contributions, it's reassuring

 

[lb63640]

LOL! My husband always want to use his air compressor when I open a dirty PC on my workbench. I always have this Tim "the toolman" Taylor vision in mind of the PC flying off the bench, or parts bursting off the mobo. Now, we know the awful truth---mighty blasts of air are NOT good for a PC when attempting to clean it.

 

[LawnBoy]

I use air compressors to clean PCs all the time. If you keep the pressure less than about 30 psi, the only issue is oil or water coming out of the hose. A $10 dryer cartridge bought at your local hardware store will solve that.

 

[malagash]

Somehow I doubt that the buddy that took the AC to his tower was remotely qualified. He "just likes to see teh dust fly"...
lol... Need I say more?

 

[ceh4702]

Compressed air in an air compressor can have several problems. Somtimes they add oil to the air. Compressed air often has moistrue in it as well. Besides that, too much pressure is too hard to control. Many air compressors are so strong that they can cause embolisms under the skin if used to blow dust off a human.

If you do not like my post feel free to point out your opinion or my errors.

 

[malagash]

ceh4702:

Trust me, the user has learned his lesson well by way of the expense incurred to diagnose the problem and replace the psu.

As for

If you do not like my post feel free to point out your opinion or my errors

This is not a forum for criticizing member contributions; your points are well taken.

 

[LawnBoy]

Many air compressors are so strong that they can cause embolisms under the skin if used to blow dust off a human.

Y'know, I've been hearing that for over 30 years, but I have yet to know of someone that it actually happened to...
Not a flame, just a comment.

 

[SkipCox]

Injuries from high pressure, high volume air lines are common. The skin splits and the compressed air takes the path of least resistance around muscle tissue and bone. Time lost from recovery is significant. More likely than a worker blowing dust off his clothing is the case when another worker is trying to be cute and blows the compressed air at a co-worker at close range.

Hi volume air supplies @ 180-200 psi are dangerous. I've also seen pc's blown off benches/tables and blown across the floor a couple feet.

Condensation in tanks and lines along with compressor oil residue is a fact of life...it's just best to pay a few bucks for canned air for the jobs that require blasting dust out of a pc.

The compressed air used by the op's husband may or may not have been responsible for the demise of the psu but, it's a good idea to play the odds and use the compressor to clean the floor and workbench...not the family computer.

Skip

http://skipcox.net