Flaky Problem 3

[goombawaho]

New" computer with new motherboard, older memory, power supply and processor.

I have a theory on the cause of this problem, but let me mention the symptoms and see what you think.

It worked great for a month - no problems at all.
Now getting the following symptoms:

Sometimes will not start to boot (does not finish POST), hangs
Sometimes starts to boot and hangs at XP splash screen
Sometimes get a pixelated POST screen when it hangs
Hearing a faint hissing from the power supply when the PC is off
Getting a "power surge on USB hub" when PC does boot with ALL USB devices disconnected.

My theory - power supply (since it is an older unit and it's making a slight noise).

Just don't have another power supply that is easily accessible to test with and don't want to buy a new one unless I feel it's very likely the cause.

 

[kjv1611]

I agree on the PSU being likely culprit. At first, I was thinking RAM, ... then maybe graphics card/chip... but the PSU sounds really likely. And if that thing goes south quick, it could take some of the other parts with it - so just keep that in mind for sure.

If the system doesn't require too much power, you could easily (I think - haven't bought one now in probably 5 or 6 months, minimum) for around $30, shipped, from NewEgg.

 

[kjv1611]

I had a couple that were more or less generic, cheap, whatever word you want to use, PSUs that came free with cases several years back. One was for me, one for another person. I learned my lesson with those, and got more recognizably named PSUs. At the time, think they were thermaltake (the ones that were good). The bad ones came with "deals" I got on cases by a company called SkyHawk... which I think also changed its name later or someone else bought it. The cheapies worked for 2 or 3 years, but when they went, they went out with a BANG!

 

[Noway2]

Hearing a faint hissing from the power supply when the PC is off

Hissing from a switch mode power supply is a classic leaking capacitor symptom. You probably have excessive ripple on the supply while it is running causing the other malfunctions.

 

[cdogg]

The problem in those situations is by the time you realize it's the power supply, it may have already damaged other components. I would definitely start with replacing the power supply followed by the video card, motherboard, and then CPU. Of course, you may want to pull the memory at this point and test it on another system (not the current one, as that will be unreliable) before you buy the power supply just to be safe.

-Carl
"Windows has detected you do not have a keyboard. Press 'F9" to continue."

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[kjv1611]

 

[goombawaho]

Ok, so I got bored and aggressive and pulled a power supply out of another machine (labor intensive - a long story) and am now posting from the afflicted PC. So, it's behaving with its borrowed power supply. I'll restart it a few times and let it run and see if anything seems hosed.

I really hope nothing else is blown since I just built this PC for the price of a $45 ASUS mobo. Everything else was cobbled together. So, I blame myself for starting with an old power supply.

The old power supply was an Antec SmartPower 350, so not a cheapie, but nothing lasts forever and it was part of a used computer when I got it. Could have been running 24/7 for a long time, so........

Thanks for confirming my gut feeling. BTW, I NEVER use my (cheapo) power supply tester to VERIFY power supplies as being good. I only use them to condemn a power supply as being dead. You need one of those fancy, expensive ones to verify power supplies.

 

[Noway2]

If you have a good collection of resistors and access to a halfway decent o-scope, you could monitor the supply output while loading it both at near full load and at a very light load.

Fortunately, most electronics today often times incorporate small linear regulators at the board level to provide lower "core" voltages (e.g. 1.5V or 1.8V) while still using 3.3V for I/O. As long as these weren't stressed too badly (i.e. a short of the rectifier circuit passing AC) there is a good chance that they survived.

 

[goombawaho]

I'm not quite that sophisticated, but that's interesting.

I think I should get a star for answering my own question. I'm haven't replaced the power supply yet. I just put a temp one in and it's hanging outside the case. Hopefully I didn't declare victory too soon.

 

[goombawaho]

The PC is behaving now with the new power supply, so I think this issue is closed. Thanks for all the responses.

 

[danomac]

FYI - I've had 4 out of 5 of those symptoms and while my power supply was fine, my video card was not. Not sure why I got the USB power surge, but replacing the video card made all the problems go away.

You might consider changing the video card as a safety precaution...

 

[goombawaho]

Well, Mr. Troubleshooter (me) says:
1. The problem is now gone with only changing to a new power supply
2. The video card is integrated so that would be a big problem
3. The motherboard and thus the video card is new

I will confess here if there are more problems, so you will be able to say "I told you so" if I am wrong.

I paid myself a lot of money to troubleshoot this problem, so I'd better have gotten my money's worth or I'm going to be realled ticked at me.

 

[danomac]

Haha, I know that feeling...

It was an old GMA video chipset that fried - I just wound up putting a budget video card in it.