How To Tell If A CPU Is Bad

TR2

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Dec 30, 2012
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This is an economic build for a friend 2 ½ years ago. (Total cost was about $275.00)

Motherboard: ECS MCP61M-M3
CPU: AMD Phenom II X2 550 black edition 3.10 GHz
Memory: AData 4 GB X 2 = 8 GB total
Hard Drive: Seagate 500 GB SATA HD 7200/16MB/SATA-6G
Video Card: ZOTAC GT220 Synergy Edition 1 GB DDR3
Power Supply: Diablotek 400W
System Case: Diablotek (a small one)

3 days ago:

My friend was browsing the internet, clicked on a link. The monitor screen went dark, showing some lines of words, then there was no display at all. The machine was still running.

He turned off the computer by pressing the power button. He tried to turn it on again. Failed.

Last night:

I tried to turn on the computer by pressing the power button. All fans (power supply, CPU and video card) were running. No display (from either the video card or onboard VGA). The power indicator on the front panel was NOT lit. The indicator on the keyboard was off.

I replaced the hard drive with a brand new SSD. Same as above except that the power indicator on the front panel was blinking. Now the optical drives make some clicking noise.

I took out everything (except for the CPU which is much harder to take out with the fan installed) from the motherboard (power connectors, memory modules, optical drives, hard drive or SSD for now, video card, TV capture card, etc.), and put them all back. The result was the same as above.

Now I disconnect the CPU fan on purpose and turn on the power. Everything is the same as above. The weird thing is that the CPU heat sink is not even warm after a couple of minutes without the CPU fan blowing.

I suspect that the CPU is fried. But how can I tell? Did I do enough to prove it already? Is there anything else that could be bad? What went wrong? Why the computer could not start?

Thank you all for reading this post. All replies are greatly appreciated.


 
Solution

Fans and other motors can work seemingly fine even with really dirty power like unfiltered half-wave-rectified voltage straight out of an AC transformer where the motor receives no power whatsoever (0V) more than half the time. Digital electronics and local voltage regulators on the other end have much tighter tolerances: the official ATX spec requires that the 12V rail be regulated within 5% (0.6V) from nominal and the switching noise/ripple must be less than 120mVpp on top of that. A PSU with cooked capacitor will have a very hard time meeting the 120mVpp ripple spec (that's when PCs start...

InvalidError

Titan
Moderator
Most likely problem: your friend's crappy Diablotek PSU died - systems failing to power-up cleanly and reliably (ex.: power LED briefly blinks on when you press the power button but everything shuts down almost immediately) is the most common sign of PSU problems in a formerly working system.

If your friend is lucky, the rest of his PC's components are still fine. If he isn't, the PSU may have taken a few other parts on a trip to the graveyard with it.

If you remove the PSU's cover, you will likely find out that the output filter caps have leaked. Two to three years is a pretty common time frame for this to happen on lightly loaded crappy PSUs.

Usually, PSU output caps failure to the point that the system will completely refuse to turn on is preceded by weeks if not months of progressively more frequent random shutdowns and reboots. Repairing or replacing the PSU during that time will usually save the system. Continuing to run on a marginally stable PSU until it becomes so unstable it is not even able to boot anymore may expose components to nasty voltage transients.

Caps are the engine oil that keeps the PWM operating smoothly. If they go bad, all sorts of weird things start happening and unless fixed in a timely fashion, permanent damage and catastrophic failure are the most likely outcomes... if you run an engine with low/no oil, bearings eventually seize and that's game over, same goes for PSUs once the output caps are too far gone.
 

FX6350

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Well when you buy him an atrocious power supply, what do you expect? Buying an expensive system and a bad PSU is like using an airplane with rollsroyce jet engines, and using really polluted fuel..
 

TR2

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Thank you all for your replies.

1. All components (including the "crappy" PSU) came in a bare-bones kit except for the video card which was on sale at the time I bought it.

2. If the PSU is bad, how come all fans are still running and the optical drive doors can still open? Same question for the motherboard.

3. I happen to have an extra PSU so I will try to install a good one to see if it works.

Any other suggestions?


 

InvalidError

Titan
Moderator

Fans and other motors can work seemingly fine even with really dirty power like unfiltered half-wave-rectified voltage straight out of an AC transformer where the motor receives no power whatsoever (0V) more than half the time. Digital electronics and local voltage regulators on the other end have much tighter tolerances: the official ATX spec requires that the 12V rail be regulated within 5% (0.6V) from nominal and the switching noise/ripple must be less than 120mVpp on top of that. A PSU with cooked capacitor will have a very hard time meeting the 120mVpp ripple spec (that's when PCs start crashing/rebooting/shutting down) and could even put the output outside the nominal 11.4-12.6V window. If the PSU is unstable due to insufficient output filtering, PWM oscillations as its feedback loop fails to stabilize could be well beyond the 11.4-12.6V range - both above and below.
 
Solution

TR2

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Thank you very much for your thorough explanation.

1. I asked my friend on the phone and he said the computer never shut down or rebooted automatically before. It never had any problem until now.

2. I opened the power supply unit and cannot see anything abnormal. There is some off white color (yellowish white) stuff on some of the parts. I touch it and it is dry. I think it is just something the manufacturer used to stabilize or to insulate the parts. I wish I could post some pictures here but I don't know how to.

3. My personal opinion is that regular computer part (such as CPU, motherboard, memory modules, hard drive, video card. etc.) are not that easy to break. The part that will most likely break first is the PSU. I have seen a few other computers like that before.
 

InvalidError

Titan
Moderator

If capacitors leaked, they would usually do so through the pressure relief pattern usually stamped on the top. The dried-up electrolyte would be yellowish or brownish colored and very brittle. If the stuff you mentioned is either solid/plastic-y or rubbery, it is indeed some sort of cement manufacturers put in there to relieve vibration strain on the components' pins.

Some capacitors have a valve built into their end-cap (the part that sits on the PCB) or in some cases, the capacitor shell pops off the end-cap. These might not be quite as visible. Depending on construction and how tightly they are sealed (or not at all with a bad end-cap valve or seal), it is also possible for capacitors to dry up without showing signs of leakage but I have not personally seen this.

Unless the caps have a low-pressure leak, I would expect them to at least show bulgy tops. Good electrolytic caps have flat tops (minus the pressure relief stamped pattern) and the bulge indicates that internal pressure has gone high enough to round it off.
 

TR2

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I looked at the inside parts of the PSU again.

1. The stuff I was talking about is cement indeed.
2. All the tube-shape (or cylinder shape) capacitors have flat tops.
3. However, I am 100% sure this PSU was a refurbished product because (a) the seal was already broken before I opened the cover and (b) the two aluminum pieces inside the PSU are badly scratched. (Note: The PSU was already installed in the system case when I received it. Now I know that was the way CompUSA.com—now, TigerDirect.com—tried to get rid of their junk. Of course, the whole thing was very cheap though, but they should have mentioned this was refurbished.)

With all the things said above, I will install a brand new Ultra 600W to one of my existing systems and take the Thermaltake 450W out from there to replace this broken one we are talking about.

I got a couple of new SSD’s to upgrade my existing systems too. It may take me a whole week to work on all these things but I am sure to come back here to report the outcome regarding this broken PSU.

Thank you again for your help.
 

TR2

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I switched to a new power supply yesterday. No luck. It was exactly the same as before.

All fans (PSU, CPU and GPU) are working fine.

The mouse and keyboard have no lights at all.

The system light blinks.

The optical drive lights went on and off a couple of times in the beginning. The drives made some cranking noise when the lights going on and off. A little while later, both optical drives are normal. The doors can open and close normally.

The hard drive feels like it’s spinning.

No display at all.

Like last time, I disconnected the CPU fan on purpose. The heat sink warms up a little bit after quite a few minutes. Just lukewarm, not hot.

Now I think it could be the hard drive that went wrong. I had this experience before as mentioned below.

http://www.tomshardware.com/answers/id-1896289/computer-suddenly-died-board-video-display-problem-cmos-battery.html

However, before I started this thread, I already disconnected the hard drive and installed a brand new SSD there for testing purpose. It did not work at all. Everything was the same as described above.

One more thought: could it be that the system BIOS was ruined while my friend was clicking on the website link I mentioned in the opening post???
 

TR2

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I did not plug in the speaker this time. I did plug it in last time but I did not turn the speakers on. I will try it tomorrow.
 

TR2

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I got some time to work on this broken computer again today.

(1) I plugged the speakers to the computer and turned on the speakers before I turned on the system. The speakers only had a little "pop" sound which normally indicates the speaker is turned on and connected to a system. There was no beep sound of any kind at all.

(2) All three indicators on the keyboard (Num Lock, Cap Lock and Scroll Lock) blink intermittently this time. None of them was on at all the last few times I tried to turned on the computer many days ago.

(3) Both optical drives make intermittent cranking sounds as long as I left the power on. I did not leave the power on for very long though.

(4) All fans are working fine, including the power supply fan, GPU fan and CPU fan.

(5) No display signal at all.

I think the problem is either on the CPU or the memory modules, most likely on the CPU because it does not get hot enough when I unplugged the CPU fan on purpose.

I do have two more computers with AMD CPU's but I don't really want to take either of them out for testing purpose on this broken computer. One had been installed with a fancier fan which would require me to take absolutely everything, including the motherboard, out before I can remove the CPU. On the other one, I have data that is important enough for me not to mess it up at all if not absolutely necessary. I would rather buy a cheap AMD CPU to replace this one. But I have to shop around to get a really cheap one. Fry's is good place to get one of these but unfortunately the closest one is more than 25 miles away from where I live so I consider it a bit of inconvenient.
 
G

Guest

Guest
This problem is not rare but in laptops: BGA problem, the analogue is a chipset problem. I think that is the reason for your system light blink + no display signal.
The chipset installed in your MB is a NVIDIA graphics oncard. So, I'm pretty sure now it burned = no display signal.

Edit:
http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?detailid=1006&CategoryID=1&DetailName=Bios&MenuID=19&LanID=0

The chipset on a laptop MB is named BGA, and it is responsible for graphics output (and control others I/O). Your friend's MB is old and the chipset on it responsible to control the communication between the MB and the GPU burned.
 
G

Guest

Guest
Sometimes, it is possible to remove and install a new BGA on a laptop MB, but almost in every case it is too expensive. But I've never hear about remove a chipset from the MB for deskptops, and it wouln't be worth. Tell him to upgrade the MB.
 

InvalidError

Titan
Moderator

The Power-On Self-Test beeps come out a "special" motherboard header for an internal diagnostic and basic sound speaker - the pins for it are located in the case switches and LEDs header cluster. The PC-speaker used to be standard in PC cases ~15 years ago but most newer cases omit it. You will not hear output from those pins through the rear audio connections unless the motherboard routes PC-speaker output out through audio jacks and enables it during boot or you installed a jumper cable to route the PC-speaker output through your discrete sound card if you have one.

Other options aside from busted CPU are busted motherboard or possibly both. If you are certain the case LEDs that plug into motherboard headers are plugged in correctly yet they do not light up while everything else appears to be getting power, I would suspect a motherboard issue.
 

TR2

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It seems it's most likely the chipset on motherboard has been fried. This makes a lot of sense to me. I will shop for a cheap motherboard to replace this one. The whole set is cheap anyway. I kind of regret that I did not spend just a little more money back then to buy a better barebone kit. For example, for $25.00 or $30.00 more I could have bought a different kit with an I3 processor.

If I can see a good CPU+motherboard combo, I probably will buy the whole set. Again, Fry's is a good place to shop for something like this but I rarely drive to the shop. Any online purchase recommendations will be welcome.

Thank you guys very much for all your help, especially to InvalidError who has answered basically all my questions from the very beginning.