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Burning smell from computer please help

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October 18, 2011 5:32:43 AM

Hello,
I noticed a couple of days ago a burnign smell in my room but didnt notice anything. I tried later that night to turn on my pc and the light came on and it switched off within seconds. Was told it was the power supply, changed that out and now I within 10 seconds of the pc being on, all the fans but the pcu fans turn off and the monitor and the keyboard wont come on.
I can unplug the monitor and it lights up shows power just no display but the lg display and the keyboard will light up when i plug and unplug it. Also since changing the psu the ethernet cable doesnt light up anymore? please help me
girl in distress

(System specs pasted from other thread by moderator)

Specs:
HP Pavilion a6720f (Phenom X4 9950 2.2 GHz)
Overview User reviewsSpecsPart Number:0884420456179.General
Platform Technology AMD LIVE! .Type Personal computer .Recommended Use Home use .Product Form Factor Tower .Width 6.9 in .Depth 16.3 in .Height 15.2 in .Localization English / United States .Desktop type Budget desktop system .Processor
Type AMD Phenom X4 9950 / 2.2 GHz .64-bit Computing Yes .Installed Qty 1.0 .Max Supported Qty 1.0 .Cache Memory
Installed Size 2.0 MB .Cache Per Processor 2 MB .RAM
Installed Size 6.0 GB / 16.0 GB (max) .Technology DDR2 SDRAM .Memory Speed 800.0 MHz .Memory Specification Compliance PC2-6400 .Form Factor DIMM 240-pin .Configuration Features 2 x 1 GB + 2 x 2 GB .Storage Controller
Type 1.0 x Serial ATA - Integrated .Storage Controller (2nd)

comp specs
it was upgraded to a 250gt video card 6 months ago

More about : burning smell computer

a c 156 V Motherboard
October 18, 2011 6:00:18 AM

Try to localise the smell. Then you have two choices. You can take the system to a computer shop and pay someone to fix it. Or you can try to fix it yourself. CAUTION: you may need the help of a knowledgable friend.

You said the you replaced the PSU and the system still doesn't work. Two possibilities here: The original PSU destroyed the motherboard when it failed. Or the new PSU was bad out of the box. Both happen more often than you would think.

When you are asking for help, always start off with the system specifications. Then, is it a new build that has never worked or is it a previously working computer that now doesn't? Is it an upgrade that you are having problems with?

The Great Carnack is dead. We need you to tell us these things. Each of the three problems above requires a somewhat different troubleshooting technique.

However, onward to some systematic troubleshooting techniques.
If a new build, start here:

Work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If no luck, continue.

If a not new build (a formerly working computer), start here:
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button, then back to 5 volts when you release the case power switch. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.

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a b V Motherboard
October 18, 2011 6:00:49 AM

... Hate to say this but when a PSU dies the way yours did it may have fried your motherboard. So it is possible everything directly connected to that board could have been sent a large surge of energy during its death that fried their circuits. Only thing I might test is your Storage devices using a USB enclosure on a working machine.

I'm not sure who made your old PSU, but for your next one make sure it is from a good company so as to lessen the likeliness of this happening. I've had one PSU die on me and it was a silent death. It just didn't turn on and I am thankful for that.
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Related resources
October 18, 2011 6:01:04 AM

If you look closely on your motherboard, do any of the capacitors looked bulged or discolored?

If so, you may have fried your motherboard.

Try not to power on too much "hoping" things will work. You may be doing irreversible damage to components.
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October 18, 2011 6:06:04 AM

It was made from Hp and bought at best buy.

The machine is acting different now.
Before the light came on but no fans at all.

now after a new power supply it powers on and light stays on and psu fans stays on. the other fans shut off within 10 seconds.
smell no burning now.
the guy that changed my psu said that there was alot of dust in my cpu fan wheh he opened it.

Omg is this expensive to fix?


old psu was antec new one we bought is coolmax 600 watts old one was 300
Thank you all so much
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October 18, 2011 6:08:37 AM

hunuok said:
If you look closely on your motherboard, do any of the capacitors looked bulged or discolored?

If so, you may have fried your motherboard.

Try not to power on too much "hoping" things will work. You may be doing irreversible damage to components.



not any bulging or discoloration.

could I have just burned up the cpu and not the mother board.

this pc is less than 2 years old :o (
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October 18, 2011 6:32:29 AM

Firstly, congrats on not frying your motherboard.

If you can use canned air (compressed air in a can), you can clean out any dust/dust bunnies from your case/components.

Make sure power is off.

Take power chords out as precaution.

Hope this helps.
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October 18, 2011 6:34:31 AM

hunuok said:
Firstly, congrats on not frying your motherboard.

If you can use canned air (compressed air in a can), you can clean out any dust/dust bunnies from your case/components.

Make sure power is off.

Take power chords out as precaution.

Hope this helps.


so you think the motherboard is ok? and I just have ot replace the cpu?
its much cheaper right?

Love the advice

Thx
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October 18, 2011 6:47:58 AM

I don't think you need to replace CPU or motherboard.

The system has a safety precaution built in where if the CPU or other components reach a certain temp (~90C), it will automatically shut down to prevent damage to components.

I would try to clean out as much dust as possible first.

Remove any large portions of dust by hand and then use compressed air to blow any residual dust. Do this outside preferably.

You should pay attention to components such as fans/air holes.

Just be careful to not to use too much force when cleaning fans. You don't want to break any fan blades.

When you power on again, do a visible inspection to check that ALL fans are turning, especially the CPU fan.

It should be a small black fan located on the upper half of the motherboard.

I have a feeling this is SO clogged, it's failing to turn, hence the premature shut down.

Good luck.

PS. If this doesn't work, your PSU could be faulty. FYI, your original PSU is better quality than CoolMax.
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a c 156 V Motherboard
October 18, 2011 6:48:39 AM

The odds that you fried your CPU are pretty low. The odds that you received a bad PSU are higher in comparison.
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October 18, 2011 6:52:04 AM

jsc said:
The odds that you fried your CPU are pretty low. The odds that you received a bad PSU are higher in comparison.

Thank you
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October 18, 2011 6:53:07 AM

hunuok said:
I don't think you need to replace CPU or motherboard.

The system has a safety precaution built in where if the CPU or other components reach a certain temp (~90C), it will automatically shut down to prevent damage to components.

I would try to clean out as much dust as possible first.

Remove any large portions of dust by hand and then use compressed air to blow any residual dust. Do this outside preferably.

You should pay attention to components such as fans/air holes.

Just be careful to not to use too much force when cleaning fans. You don't want to break any fan blades.

When you power on again, do a visible inspection to check that ALL fans are turning, especially the CPU fan.

It should be a small black fan located on the upper half of the motherboard.

I have a feeling this is SO clogged, it's failing to turn, hence the premature shut down.

Good luck.


Thank you I will try this.
The psu fans stays on the others shut off after like 10 secs. do you know why my keyboard and monitor arent coming on and the eternet cable area isnt lit up like normal.

Thanks
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October 18, 2011 6:57:03 AM

Quote:
do you know why my keyboard and monitor arent coming on and the eternet cable area isnt lit up like normal.


Windows needs to FULLY boot (ie login then get to your desktop) in order for keyboard/mouse/LAN (ie internet) to work.
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October 18, 2011 7:01:38 AM

hunuok said:
Quote:
do you know why my keyboard and monitor arent coming on and the eternet cable area isnt lit up like normal.


Windows needs to FULLY boot (ie login then get to your desktop) in order for keyboard/mouse/LAN (ie internet) to work.

I will try all of this tomorrow and let you know.

Thanks bunches.

someone said try resetting everything like the memory and all that.
How do I know for sure if the guy that installed my psu clicked everything in the right way?

thx
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a c 117 V Motherboard
October 18, 2011 7:03:34 AM

That mobo is a Pegatron M2N78-LA and from what i've been reading is notorious for dying.
Google it you'll get tons of links confirming it especially HP forums.
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October 18, 2011 7:07:28 AM

Quote:
How do I know for sure if the guy that installed my psu clicked everything in the right way?


Check for any cables that are not plugged in/loose.

Also, Davcon has a valid point.

"Brand" PCs are renowned to use cheap/inferior parts to maximize profits.

If suggestions don't work, you may need to go to HP authorized dealer to diagnose problems.
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October 19, 2011 12:25:54 AM

hunuok said:
Quote:
How do I know for sure if the guy that installed my psu clicked everything in the right way?


Check for any cables that are not plugged in/loose.

Also, Davcon has a valid point.

"Brand" PCs are renowned to use cheap/inferior parts to maximize profits.

If suggestions don't work, you may need to go to HP authorized dealer to diagnose problems.



computer is cleaned out no dust anywhere
it wont work
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October 19, 2011 5:21:09 AM

Sorry I couldn't help.

I think it's a bad motherboard or PSU.

As the PSU was the last component you replaced (and cheapest), change the PSU.

If that doesn't work, you will need to take it to HP.

They may need to swap motherboard.

It's not the answer you wanted to hear I know.



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