Hi all:
I'm concerned about my computer showing me ocasionally that the 12v reading is low.
I became pretty obsessed with all the voltages being normal since a cheap PS burnt me a CDROM and a CDRW.
This is my new system i've built months ago, but it includes older parts:

ATX Power Supply 300W L&C (by Codegen)
Celeron 1.1 Ghz w/ Power Cooler ~5000 rpm
M/B Soyo 7VBA-133U (4 USB ports)
384 MB RAM PC133 (1 stick x 128MB Kingston, 1 stick x 256MB Samsung)
Maxtor HD's models 31024H2 (10GB) & 90432D3 (4GB)
LiteOn CDROM 52x
Samsung SW224 CDRW
1x Floppy drive
Pine GeForce 2 MX 200 32MB
ISA Network card
ISA Sound Blaster AWE64

I have set the VIA Hardware Monitor (included with the Soyo CD) to start with windows, so it's checking the system constantly. I've read somewhere that the maximum tolerance for a PS voltage is +/- %10
But when it begins to fail, it begins to go up and down, and once it reached 10.11v, that makes 15.75 percent less from normal (of course when this happens i immediately shut down the PC)
When normal, it stays in the 11.85 - 11.50 range (even when failing never surpases 12, always goes lower).
The other time it happened, i unplugged the four IDE devices, and went to read the voltage from BIOS setup (instead of VIAHM in Windows)
It were then at a steady 11.83 or so.
Then began adding devices one at a time (power off between of course), and when all were plugged, it kept normal.
My couple of questions are:
1 - Could a LOWER voltage fry a component (like a HD) or just make it cease working causing as worst a data loss (so i can be less paranoid and solve this problem more chilled)
2 - Both HD's were in the system that fried. But since they survived i reused them in my new computer. Could them however be malfunctioning and drawing more current from PS hence explaining the overall lowerage?
My primary concerns are both the CDROM and the CDRW that are new, i would not risk them for a crappy 4GB HD.
3 - I was yesterday using the machine to repair a third disk i have, kept running Powermax for 3 hours, then reconnected the above mentioned HD's and kept running normal for about 1 hour without use, then suddenly the voltage dropped and i HEARD one HD (couldn't tell which one) spinning lower intermitently, just when i sitted down to use a program. Meanwhile the voltage dropped in VIAHM and the onboard alarm sounded. So it seems that the lowerage occurs when one of the HD's is in use (the 4GB one i think).

Any hints?

Lower than expected voltage should not "fry" a device, but if it is a data device then data loss/corruption is almost certain.

As to one device pulling more than normal and drawing down the entire "leg", yep it is possible...especially if it something like a drive. The drive will try to keep the speed correct, but failing that it will draw a little more "juice" to try an keep going. Also if it is trying to spin up, and the motor is getting a little worn out (bearings starting to fail, etc), it will be harder to start which would require more to get it going.

Now without actually being able to measure what each individual drive is doing, I would say it isn't any one of them, but all of them together. If you suspect the 4GB drive is the one with the biggest draw, try running without it for a while. It may be fine by itself, because there would be a lighter load on the the 12V leg and it could take as much as it needs. So test the others together.

Remember, other 12V devices are the floppy drive and the various fans......so don't leave them out of the equation.

Thank you very much mjc, I'll try tonight what you suggest.
I still can't explain why removing all drives and then adding one, starting, adding other, starting again, etc. solved the problem once.
Couldn't it be just a bit loose molex cable?
NOTE: They are 2 lines of cables that go out from the PS, both with two HD/CDROM connectors and one floppy connector each.
Using one line with both HD's and the other with the two CDROM units.
So it's almost the same as having two splitters, which makes me wonder about the quality of this PS, i've seen others from this brand around many times, but does anyone know them around there?

I'm however looking forward to buy a bigger HD (say 40GB), and remove both present ones. But even if i decide to spend that much cash i must be completely certain that this problem has nothing to do with the Power Supply by itself (if i spend a lot of cash on a large HD and when popped in it burns, i can assure i'll quit computers forever, quit my job, throw my computer by the window and go directly to a mental institution to live there forever :) )
I've had soooooooooo much computer related troubles on the last months since i first thought in replacing my old Pentium 200, that i can't take it anymore.
But, how do i test if the problem is the PS since when devices are unplugged the voltage is normal, and even with all there the problem is ocassional?? :confused:

Short of having some sort of external monitoring of each device you will probalby have to do the trial and error method...but from what you are describing I would be inclined to just replace the PS, because even if there is nothing wrong with it it may be that the current supplied by the 12V leg is borderline to your needs.

OK, tested last night:
At first removed the 4GB one: same deal.
The voltage kept going down, and the same sound of the HD spinning lower and higher.
NOTE: it's quite difficult for me to explain with the exact words you would use since english is not my native language, but i hope you understand what i mean.
It turns out that the problem is the 10GB one.
Removed it, and used a third spare HD to boot, with the 4GB one as the slave, and both CD's also connected on sec. IDE. Kept running for quite a while (about half hour) and never came lower than 11.50
Also the sound coming from the HD's is constant.
So i'll be buying a new HD soon, (i was planning to do however), and maybe i'll post a new thread under Buying Advice forum on the next days.
If later it turns out that the problem is the power supply, i'll have to replace it also, but i don't think so since i've seen others of very poor quality running 4 IDE devices at the same time without problems.
(although mine could be bad, which wouldn't surprise me since i have bad luck with computer parts lately).
I'm calm now because i know the new HD won't fry as soon as i plug it.
Many thanks for all your advice, you've been helpfull.

I have an update on this issue.
I began inspecting further and realized that the spinning variations didn't came from the HD's!! It was obvious when both were unplugged and i stuck my ear really close to the case. It was the damn cpu cooler!
Removed it and it had plenty of dust (GREASY dust...argh)
Had to unscrew it from the heatsink and clean both (wish i had a tube of compressed air...i'll buy some for next time).
I've set it in place again and the spinning became constant! And the voltage didn't dropped again.
Maybe it's just coincidence, but i'll test the machine throughly by the weekend. It was an incredible amount of dust for a machine with less than five months of use.
Could this have been the problem? Maybe the cooler was pulling more current to keep spinning because of the dust...

Since it is also 12v, yes it could be the problem......

Well, it turns out that i'll have to replace the PS. The other day the voltage dropped again and this time the cooler is clean.
To ensure it was not causing the problem i intentionally slowed it down a bit with my finger, and the voltage didn't dropped. Maybe a PS component begins to fail under certain conditions.
Also when i take the PS off and move it out of the case sometimes the system doesn't boot, so it isn't working fine.
The problem is that this brand (L&C by Codegen) is the only one available around here, the others are even worst.
I've not seen Antec or the others you frequently mention anywhere :(
And i wouldn't order it for shipment since i'm afraid the trip would get it damaged (plus it would be expensive).
So i guess i'll have to go with this brand again. :mad:

Check out this link for more info on power supplies:

http://www6.tomshardware.com/howto/02q4/021021/index.html

You may be able to find one of the other well rated brands in your area. Also, power supplies are not too fragile, so they can probably handle being shipped if they aren't tossed from high buildings.:)

Budfred

Didn't find any i've seen before, but thanks anyway, that's a good reference which may come in handy.
And about buying outside the country, the real problem is the price which i couldn't afford (in dollars + customs taxes).

Last time it happened i forgot to say that it did with the new 60GB HD alone, so it leaves the older ones out.