Power Supply Issues???

[william_321]

hi,
i'd really appreciate if anyone can help me

recently i've been experiencing some trouble with my computer but i cant seem to narrow down the exact cause, i have some insights though :confused:

its like this
the last couple of weeks i had been working and suddenly my pc rebooted itself, i thought i had been using it too much and just turned it off, but day after day this "erratic behavior" kept repeating itself, and after a few tests :) i noticed certain symptoms.

1. sometimes when it reboots itself it stays blocked, i mean the power led stays on but no fans work, nothing moves, after a while (1 min or so) the computer starts again, its just like it "turned off" momentarily, i've noticed a click sound that comes out of the HDD when this happens
2. this behavior is totally random, it doesn't matter if i'm on the internet or just listening to some tunes, one time i was checking the BIOS configuration and it just "turned off"
3. i've checked RAM with memtest86 and its ok, ive also run some HDD tests with a maxtor tool and its also ok
4. in the past i had to replace the PSU due to similar problems (but with little effect)
5. i read some troubleshooting guide about PSUs and found that you can measure voltages in the connector in order to rule out PSU issues, i measured the +3.3 +5 and +12 pins and they were ok but i found that the "power good" pin would change its voltage everytime the erratic behavior was present.
5. i also found that if i plugged in any other device such cable modem or USB storage device it would also cause the pc to reboot, most of the times
6. on a desperate attemp to rule out OS issues i formatted and re installed everything, but sadly :mad: the erratic behavior continued

i'm really not sure what it is that's causing this, so any help in the matter would be really appreciated

anyway these are the pc specs
p4 2.8Ghz
intel motherboard 865gbf
maxtor 80gb hdd
lg dvd optical drive
1x512mb ddr ram
simple case w/ 2 fans and a 550wtt psu

[mjc]

The "power good" shouldn't change that often...it should only change when it is first powered on or when the machine is being rebooted.

Now is what you are seeing the result of the reboot or the cause?

Hard to say without constantly monitoring ALL the voltages to see if there is enough of a drop on one of the other rails to trigger it. I'd say the best thing to do would be to swap out the power supply with a known good one...because without a set of dedicated equipment, it would be nearly impossible to do that level of monitoring.

There is also a chance that the motherboard could be the source of the problem...but again, without some means of nearly constant monitoring it is going to be hard to pin down, unless it is something obvious, like bulging capacitors.

[william_321]

Hard to say without constantly monitoring ALL the voltages to see if there is enough of a drop on one of the other rails to trigger it

i agree, constantly monitoring voltages requires special equipment, i'm trying to troubleshoot the PSU using a voltmeter, i've also inspected the motherboard for bulged capacitors but they all seem fine, no bulging no leaking

i believe the power good voltage drop is the cause, but i'm not sure why does this happen

[kiosk]

I think that this has more to do with electrical noise not being properly filtered out, rather than massive voltage drops. The former would be caused by cheap electrolytics that fail all too often these days. :(

[mjc]

A borderline or overloaded PSU can drop one or more rails...this could fool it into thinking that it has been rebooted. Also, a power supply that is weak or failing on just one rail can 'spontaniously' reboot...

Overall, I'd say the chances are, since there is no evidence of failing caps on the motherboard, that it is a power supply problem.

What brand is the current power supply?

[Sylvander]

IN GENERAL...

If you load and run Knoppix from a Knoppix Linux Live CD (http://www.knoppix.org/), and the problem continues, then it is indeed a hardware problem.

If it magically ceases, then it isn't a hardware problem [HDD not included], but is most likely a [Windows environment] software problem.

Not much doubt yours is a hardware problem.