Computer Questions
Aug. 17th, 2008 09:31 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
willow_redAs I might have mentioned to some of you, my desktop crapped out about a month ago. ![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
j_b suggested it might be the power supply, and I am inclined to agree. I copied everything from that hard drive onto my laptop to be safe, and then tried to start up the desktop last night, after it had been "resting" for several weeks. It worked (huzzah!), but the internal clock had reset itself to 11:00pm on December 31, 2000. I know approximately zilch about power supplies, so here are my questions:
1) Would it be just the power supply getting flaky that would cause the clock to reset, or does the battery on the mobo need to be replaced too?
2) I can't find a label on the power supply itself, but the parts list pasted to the inside of the box says it's 250 W. I've started looking for replacements, but haven't found anything that small. The smallest I saw in the Tiger Direct catalog (that conveniently arrived in the mail last week) was 400 W. Is bigger better, or even safe?
3) Do physical dimensions tend to differ on these? In other words, do I have to make sure I buy one that fits in the box?
4) Should I be looking for a name brand (if so, which one(s)?), or are power supplies pretty much all the same?
5) With a dying power supply, is it safe to leave the computer on when I'm not home? I'd prefer not to set my house on fire, especially with Akito locked inside.
6) Is there anything else I should know that I haven't asked about already?
A big thanks to anyone who can help me out with some advice here!
j_b suggested it might be the power supply, and I am inclined to agree. I copied everything from that hard drive onto my laptop to be safe, and then tried to start up the desktop last night, after it had been "resting" for several weeks. It worked (huzzah!), but the internal clock had reset itself to 11:00pm on December 31, 2000. I know approximately zilch about power supplies, so here are my questions:1) Would it be just the power supply getting flaky that would cause the clock to reset, or does the battery on the mobo need to be replaced too?
2) I can't find a label on the power supply itself, but the parts list pasted to the inside of the box says it's 250 W. I've started looking for replacements, but haven't found anything that small. The smallest I saw in the Tiger Direct catalog (that conveniently arrived in the mail last week) was 400 W. Is bigger better, or even safe?
3) Do physical dimensions tend to differ on these? In other words, do I have to make sure I buy one that fits in the box?
4) Should I be looking for a name brand (if so, which one(s)?), or are power supplies pretty much all the same?
5) With a dying power supply, is it safe to leave the computer on when I'm not home? I'd prefer not to set my house on fire, especially with Akito locked inside.
6) Is there anything else I should know that I haven't asked about already?
A big thanks to anyone who can help me out with some advice here!
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no subject
Date: 2008-08-17 06:03 pm (UTC)no subject
Date: 2008-08-17 06:40 pm (UTC)Most power supplies are a standard size/form. Unless your box is a prefab (aka, some wierd configuration from dell/compaq/apple where they only want you buying from them) you can pretty much buy one off of any shelf at best buy. The main thing to check is whether or not your computer uses an AT or an ATX power supply. Honestly I haven't seen an AT motherboard since the 90s, but I don't know how old your box is...
bigger is better where wattage is concerned. They pretty much don't make 'em smaller than 300W these days because all the new hard disks and video cards are power hungry. my computer doesn't even run without a 500W+ power supply due to the video card.
i wouldn't leave it on if I were you. It won't burn your house down, but if the fan is dead (the most common reason why power supplies fail) it could over heat your computer and damage the motherboard or other components.
Personally I wouln't worry about losing the system clock. It does point to a dying mobo battery, but its not like it would really effect you if you had a workign power supply.
no subject
Date: 2008-08-17 08:23 pm (UTC)Might as well replace the mobo battery while you're in there, it will fail eventually. If it's a coin cell, be aware that there are many kinds of coin cell, so take the old battery with you when you go to get the new one. Radio Shack near 28th and Pearl is almost certain to have the right kind.
2) I can't find a label on the power supply itself, but the parts list pasted to the inside of the box says it's 250 W. I've started looking for replacements, but haven't found anything that small. The smallest I saw in the Tiger Direct catalog (that conveniently arrived in the mail last week) was 400 W. Is bigger better, or even safe?
3) Do physical dimensions tend to differ on these? In other words, do I have to make sure I buy one that fits in the box?
Yes, sizes do vary. Also, the big fat connector that goes from PSU to mobo also varies. And in some newer machines, the CPU has a separate and different power connector than the mobo. Safest to take the old power supply with you when shopping and make sure everything matches. If you can't see it physically, then at least find a picture of all the connectors and make sure they match up.
Also be sure the new PSU has enough of those clear/white trapezoidal four-hole hard drive power connectors to power everything in the case. Some of the ultra-cheapo PS's skimp on those.
4) Should I be looking for a name brand (if so, which one(s)?), or are power supplies pretty much all the same?
I replaced with the PSU on Se's parent's computer with an ultra-cheapo no-brand $29 PSU from CompUselessA about two years back, and as far as I know it's still running fine. Maybe I was just lucky.
5) With a dying power supply, is it safe to leave the computer on when I'm not home? I'd prefer not to set my house on fire, especially with Akito locked inside.
As far as the PSU itself going up... it's inside a sealed metal box. How exactly is it going to set anything on fire? At worst it might blow its own internal fuse, or pop a breaker in your breaker box. The fuse will go long before the cord melts. UL Listing tests for these kind of things. Also, I've never heard of a PSU failing in such a way that the circuitry remains connected to power. Electronics almost always fail in such a way as to disconnect power. Even if it did fail connected, the internal fuse would blow.
6) Is there anything else I should know that I haven't asked about already?
I'd point you to some reviews of PSU's on the net, but most of them are for power-users, 600 watts or more, so they're not much use to you. A lot of those reviews are inaccurate anyway. Still, a little general knowledge about PSUs might not be a bad idea.
If you've had the computer more than two years, you should re-grease the CPU heatsink while you're in there. This was another problem with Se's parent's computer. It was getting flaky because the CPU was overheating. The giveaway was that the CPU heatsink, which should have been one of the hotter heat sinks on the board, was actually the coolest. This showed that it wasn't pulling heat from the CPU.
Regreasing the heatsink basically involves removing the sink (usually some kind of wire clip), scraping any of the old, dried up crap off the sink and the CPU, cleaning any remaining crap off with rubbing alcohol, then squeezing a small (size of a grain of rice or BB) amount of new thermal grease onto the CPU, spreading it around to make a thin, even layer with some kind of flat tool (screwdriver works fine), and then re-attaching the heat sink. Since I'm presently not employed and have nothing better to do, I'd be happy to help you with this if you want. It's not hard, but sometimes it's easier to learn if someone demonstrates. My cell number is in my lj userinfo as always.
no subject
Date: 2008-08-17 11:00 pm (UTC)1. I can imgine a situation when flaky power supply caused the clock to fail because its power control circuit did not switch to internal battery until lowered or unstable voltage caused the clock to reset, or power supply produced unfiltered output, passing pulses from voltage converter directly to the power rail -- those pulses could randomly change the state of various signals, producing invalid clock (and possibly CMOS memory) state, causing clock to reset on next boot-up.
Some motherboards have battery sensor that can be seen in hardware monitor menu of BIOS setup or in various monitoring software, and you can always take the battery out and measure it.
2. Some geniuses produce power supplies with higher overall power, yet weird distribution of maximum current between outputs (like, can produce ridiculous amout of current on 5V rail, however lower than usual current on 12V rail). Since you had 250W power supply, I don't expect it to be a problem if you replace it with 350-400W, however it may happen if you use another 250W one.
Check the type of connectors -- usually it's 20-pin rectangular plug for motherboard, 4-pin square plug that also goes to motherboard and only powers CPU, flat 4-pin hard drive / CD drive plugs and even flatter SATA hard drive plugs, plus one small floppy drive plug. Some motherboards only have 20-pin connectors. Some video cards and even motherboard have hard drive-style power connectors for additional power.
Desktop power supplies usually have this set of plugs, however there are also server power supplies wtith 24pin (instead of 20) and 6-pin (additional) connectors. 24-pin connector is a superset of 20-pin one, however you would have to add an adapter or cable to use those, so I don't recommend a server power supply for a desktop.
Some power supplies have separate 12V rails for 20-pin connector, 4-pin connector amd hard drives (often listed as 12V1, 12V2 and even 12V3 on the ratings label). This is pretty useless if you have one had drive and no second motherboard connector, so only one of those rails will actually power the motherboard.
3. Manufacturers other than Dell are supposed to make cases compatible with a standard ATX power supply dimensions (Dell can do whatever the hell it pleases), and most of powers supplies you can find are either standard ATX or standard ATX with a huge fan strapped on it outside of the power supply case toward the _front_ of the computer case (this setup is known to cause noise and vibration because power supply is only attached to the rear panel on four screws, not to menion interfering with other parts). There is also an issue of an "optional" (what usually means "giant 120mm") fan oulet at the bottom of the power supply occasionally coinciding with just as optional support shelf in some older cases. As one wold guess, only one of those parts can be present, so check if your case keeps the bottom surface of the power supply clean of things that may block airflow.
4. Power supplies are second least reliable parts of computers after hard drives. ALL hard drives of all brands eventually fail in a few years. With power supplies the situation is slightly better -- SOME power supply of all brands and models fail (they are still supposed to fail after decades of use). Mostly I support Jon's recommendation on known-to-be-better brands, however nothing really guarantees reliability, and even a cheap power supply is usable.
6. When covering a CPU with thermal grease I usually use a piece of plastic cut out of CPU packaging. Old credit card should work well, too (it only has to have smooth, straight edge). Screwdriver is too narrow to spread thermal grease evenly on a modern CPU's heat spreader.
no subject
Date: 2008-08-18 01:41 am (UTC)DenverSop
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Date: 2008-08-18 02:25 pm (UTC)