Acceptable power supply voltages?

[67GTA]

My HP m8100n desktop has been freezing/rebooting when under a load. Most stress tests cause it to lock up/reboot. I have ruled out hdd, ram, heat, etc. I am down to either the mb or psu. I have monitored the psu voltages with software and manually with a multimeter. The +3.3v doesn't look right to me. From what I've read (I'm no expert in this area) the min value for the +3.3V rail is 3.2V. It is supposed to power the cpu, video card, and sometimes the ram. I'm guessing at idle it is fine, and runs out of juice when under a load at only 1.7V. Any second opinions?

CPU Core = 1.296V
+2.5 = 2.48V
[COLOR=#ff0000]+3.3V = 1.776V[/COLOR]
+5V = 5.68V
+12V = 11.776V
-5V = 4.672V
-12V = 11.392V

[oshunluvr]

Generally, if you're going to test the voltages to determine PSU failure, you need to do it with a meter. Mobo sensors and software are more likely to be flawed than a PSU. For example: The fact that your reading on the 3.3 sensor is almost exactly half of what it is supposed to be raises suspicion that the software is using the wrong multiplier.

However, when you combine the low reading with the lock-ups/reboots a betting man would wager a couple month's rent on the PSU being the problem.

The behavior you describe is exactly what my computer was doing until I replace my PSU. In my case, it was because it was not powerful enough. Once I upgraded, all the locking up and crashing stopped.

[67GTA]

This is a stock rig I bought from a box store in 2007. It is time for something to break:-) Those values were the same as when I checked with a multimeter, so that is two points of data. I'm pretty sure they are right. I wasn't sure of the voltage variance levels. The other values fluctuate 1%-2% with/without a load. The 3.3V rail stays at 1.776V. I've already been shopping for a psu, but I have had my eye on a system76 rig if the wife will entertain the idea...

[james147]

What wattage is the PSU? and what specs is your system? My guess is also that the power supply is faulty or not powerful enough.

[67GTA]

It is a 300W psu (the one that came in it). http://h20000.www2.hp.com/bizsupport...ctID=c01151028

[tek_heretik]

1. Proprietary machine builders use just-good-enough parts (capacitors are the main culprit, visually inspect, if you see the tops lifting [puffing upwards] or have dried brownish fluid on them, they are toast), if it makes it past its 1 or 2 or 3 year warranty, you got what you paid for and if it breaks, maybe some people are dumb enough to bring it to them so they can make another mitt full of money off the consumer. I have had many proprietary machines cross my desk and half of the time the cheesy PSU just kahked. You could buy capacitors of the same value and solder them in, but I find that to be a pain and just go for a new unit.

2. Does the BIOS not have a 'health' section, displaying readings? Voltages are usually displayed there.

3. Have you added a ton of drives over the years? Upgraded the video card, etc? More memory, added a cooling fan or two? Lots of USB gizmos plugged in? The PSU that HP put in there only came with a certain amount of overhead, why would they put in a beast PSU for double the stock machine load?

4. Check the physical design of the PSU, you may have to custom install an off the shelf PSU, Compaq, HP, Dell, etc, are jokers, they like to order bizarre screw hole patterns, oversized, undersized, etc from their suppliers. You might even need to have a Torx screwdriver handy, lol.

5. 3.3V rails supply the CPU? That's more like RAM and expansion slot power, if I am not mistaken, the CPU feeds off a 12V rail, it's surrounded by capacitors, etc, on the motherboard, for step downs and bursts of juice when needed.

[67GTA]

1.I've visually inspected everything. The capacitors look fine. A replacement psu is about $15-$20, and will be fine for this machine. I doubt it will last another 5 years:-)

2.The bios dosn't have a sensor/health section. It is pretty locked down.

3.I've only added ram. It is all still oem.

4.Luckliy it has standard screws/screw pattern (liteon) It won't be hard to replace. I've already had it out to test with multimeter

5.You are correct. After reading some newer material, the ram draws from 3.3v, and almost everything else runs from 12v in newer pc's

[tek_heretik]

1.I've visually inspected everything. The capacitors look fine. A replacement psu is about $15-$20, and will be fine for this machine. I doubt it will last another 5 years:-)

2.The bios dosn't have a sensor/health section. It is pretty locked down.

3.I've only added ram. It is all still oem.

4.Luckliy it has standard screws/screw pattern (liteon) It won't be hard to replace. I've already had it out to test with multimeter

5.You are correct. After reading some newer material, the ram draws from 3.3v, and almost everything else runs from 12v in newer pc's

Meh, the $15-20 is worth PSU doubt elimination factor. Since it is out of warranty, you can do whatever you want to it, lol, stick a little fan on the northbridge, etc, heh, maybe OC it a little. I hope I didn't sound too condescending, I always write responses with the anticipation less experienced people may read them.