Bizarre computer turning on and off (mystery problem)

N

newsposter

New Member
My newly purchased power supply tester confirms my PS is ok. I have not done any other diagnostic as I thought this was the PS all along.

Symptoms: one day a few weeks ago I went into the room and heard the computer cycling on and off. It was like the fan started whirring, the hard drive light flickered, and it was powering on and off. Approximately once every second or so. Obviously I have kept it unplugged since then except when using it. the computer operates fine from all aspects and the Asus monitor shows voltage etc as normal.

When I unplug it, I can hear what sounds like a tv or the monitor being turned off (crt type noise). however the monitor is always turned off on its front and always before the computer has completed it's turnoff. The sound comes from the full tower. I can't localize it yet.

this sound also occurred when the power supply was attached to the tester. I dont know if this rules out the motherboard or not? I also heard a high pitched whine after I unplugged the power supply and yet the tester was still plugged in.

The computer is difficult to pull out so i'll have to wait until weekend to pull it out. But how should I go about testing it? unplug all cards and drives and add back one by one? Oh I forgot, I did unplug the 2 hard drive IDE cables prior to any testing tonight.
 
If you were hearing this sound while the supply was completely unplugged from the board while testing it you have already found the problem; the supply itself. If this was only with the supply connected to the board then you would have to start looking at a possible board fault. It sounds like you have a circuit opening and closing fast like an intermittent connection(cold solder joint) to be seeing if it is isolated to the supply alone.
 
i unplugged the 20 pin from the p4p800 and used the tester. Is there anything else i should have unplugged? And why does the tester show full green lights if the PS is bad? I'm confused and thought the 11 dollar tester would be 'foolproof' lol

should i unplug everything from the PS completely then test it to see if i hear the noise?
 
The plugins for the drives wouldn't be a concern since the only current drawn from those is seen with the system running. All green shows that the power is present when tested which is good. The connector off of the supply or the board's own socket for the main power connection would be an item to look at. But you mentioned hearing the odd sound while testing. Do you have a second supply onhand to see if the supply is the problem?
 
This sort of whine is reasonably common from defective PSUs. PC Eye is correct - your PSU is almost certainly at fault, and your $11 tester isn't going to help you diagnose this sort of problem.

Best to replace the PSU. Just out of curiosity, what type of PSU is it?

If you'd like recommendations for a new unit, post your budget and system specs here.
 
no second supply available.

Antec sl400 and i can't find the receipt as I still have until 12.26.06 for a 3 year warranty replacement. Just dont know if i can dig it up so probably will just order a new one.

here's a thread about how i was trying to figure out what supply to get before I was 'sure' it was the PS.

http://www.computerforum.com/67004-replacement-antec-sl400.html

now i'm a bit uncertain about getting an antec neo like I was gonna. If this antec only lasted this long, it's a bit upsetting.

If i do get it, i was just gonna go with the 430. I dont see the need for 500 based on what others have said were my overestimations in my thread there. Or maybe just an SP 450 unless there's a reason not to.

and for the record, what good is my 11 dollar PS tester if it shows ok yet the supply is bad?
 
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This sort of whine was particularly common with some Antec PSUs. The NeoHEs are built on a completely different (better) platform than the SPs, but as i've said before I feel that there are better units available for the money.

I would personally avoid another Smartpower due to QC issues, but a NeoHE430W would be sufficient for your system. At $85, it's priced a little higher than i'd be willing to pay though.

As far as the tester goes, it will tell you if your PSU fails completely. In your case the unit works, but whines, something the tester is unable to check.
 
thanks for the info on the SP

i found the neo 430 for 63 and free shipping

and i saw your other recommendations in my post before Enhance 5150GH or Corsair HX520W and will see if i can find a good deal on them too.
 
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Those smartpower have to be the more horrible PSUs I've ever tried. I own one, that if the wires aren't placed in a precise way, the drives will either not power up, or power up and quit right in the middle of loading, and turn on and off in a countless loop.

Also, I've had the last time, the board not booting because the 20-pin was not precisly made in place. The voltages went from 11-8.5V.

So, yours is bad.
The PSU you're looking at is a fairly good one. The higher the price, the more quality and true power you're getting.
 
I never use the Smart Power or NeoHE models here. The True Power line has always shown itself to be reliable. But ceeewi1 has been seeing good results with those models for him to be stressing those. Enermax was another make that was the "gamer's choice" at one time until they slid under somewhat. We'll just have to go back to the other thread and edit the "good/baddie" list there. :eek: :P
 
Well I guess that's like saying: "the more power(12v) to ya!". :P That should work out for you. It's not a long involved process to swap a supply out. It takes more time unplugging and plugging the ac, monitor, keyboard, mouse, printer, or whatever else then to pull the drive plugs and main connector out and slide the new supply in at times.
 
PC eye said:
. It takes more time unplugging and plugging .
Click to expand...

Yes i think i'm gonna pull out the entire thing and lay it on the table. Just unplugging the 20pin was a PITA (IDE cables in the way) and no way would i want to plug it in without swinging the MB down. Also this will give me a chance to route cables better as I've gotten spaghetti in there over the years. May as well get the can of air out too.

It will be nice to not have to reach around and unplug this thing everytime I"m done with it.
 
You have dust herds clammering around inside your case? :eek: You may need an air hose for truck tires to clean out the inners now! :P At least every few months anyways you want to squeeze some air inside to keep the dust layers from growing on everything.

As far as the supply there the first thing to go after is a good replacement. You could send the current one direct to the manufacturer for repair but it's an unnecessary hassle. The prices are low enough for a new one where you can save time and hassles along with the uncertainty once you got that one back. Of the spare supplies still kicking around here for possible use as replacements in older builds they have to be 100% or they get tossed.
 
well neo solved the problem. However something is wrong. I had my asus temp warning set to 40 for the MB and it never went off...now it goes off all the time. And this is even with the side of the case just leaning up against it, not installed.

in addition to the fan in front i have another fan on the bottom rear of the case blowing the hot air out and both are working.

Would this new supply run hotter than the old?
 
If you have a manual option for temp alarm on the board set to low expect it to go off constantly. That should be set to go off around 55C or 60C in the event something does get too hot. The normal operating temp seen on a Socket 939 board was warmer then on a Socket A AMD board seen here.

Instead of 42C the new board was seen at 48C initially until installed in a better case. But that was still within normal operating temps there. I would simply raise the alarm temp up to a higher then normally seen temp to correct that fast. When your temps really do climb then you know there's something wrong.
 
so was i just lucky that the old setup never set off the 40C M/B alarm? :) Is 40C good for just 2 fans in the case?

I'll set it a tad higher, perhaps 45 just to see how things go.
 
When I was running the old case with a Socket A board I had set the alarm too low at one time for the stock hsf and two 80mm fans only there. The lack of any front or side vents saw a higher board temp of about 50C when the cpu was up into the low 60s. Suddenly the alarm goes off and the system shuts off! A look in the bios solved that fast.

40C isn't the lowest while being well within the norm there. Increasing the air flow would be sure to see that go down. For less demanding things like checking the mail and small apps you wouldn't have a problem there. But if you plan on heavy gaming and running large multimedia where the demand is placed heavily on resources better cooling wll become needed when you see temps start to soar.
 
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