When CPUs Die Do the Fans Still Come on?

Factual Questions
21

I wouldn’t trust wiring colors to be standard. You want to short PS_ON to the power supply common, which is pin 14 to pin 15 in the connector.

No offense SimonX but judging from your posts, you don’t have enough experience with electronic type stuff to do this. One slight slip and you could make your power supply die a horrible death (picture lots of smoke). Of course, this assumes that the power supply isn’t already dead.

I probably wouldn’t bother pulling everything out of the case, but I would disconnect everything from the motherboard except the memory and cpu. The power supply should at least turn on then. Even if the CPU is toast, the power supply will usually turn on. Most motherboards put out a “panic” code at that point (just a repeated beep, no pattern). If the CPU works, then you’ll get beep codes for the other stuff.

Based on the rest of this thread, I’m leaning towards both the power supply and motherboard being toasted. Probably it was one or the other that died first, and just happened to take the other one out with it when it went.

A multimeter is typically a voltmeter, ammeter, and ohmmeter all in one (hence, multi).

And wood, even particle board, makes for a decent insulated surface if you want to assemble bits on your desktop.

22

The button you press to turn on your PC. It’s connected to your motherboard, and when you press it, your mobo connects those pins together on the PSU to fire it up.

Return Merchandise Authorization. When you ship a defective part back, you typically get a code to write on the outside of the package so they know who it came from and why it’s coming back.

A multimeter can measure volts, but as the name suggests, it can also measure other things. For example, you can test a switch by setting it to measure resistance, attaching a probe to each contact, and pressing the switch (the resistance should go from infinity to near 0 as you press it).

23

Well if none is not enough, then you’re right.
I wasn’t to hip on the idea of trying to short any sort of a 350W something with a paperclip. I’ll happily leave that to the pros.
I was interested in learning about how to use the multimeter though. That’s sounds like it could come in handy. I’ve had two different computer fixing puzzles inthe past two weeks. The last one I had to try booting over and over with different combinations of hardware looking for which one was troublesome. I like to imagine that I could’ve proceeded much faster if I had had more knowledge and the right equipment.

It makes me uncomfortable to read this. I have a similar apprehension. I’ll be glad to have solved the puzzle of course, but I’d rather not shell out the cash for a replacement mobo.

I’m Googling for instructions on their use.

Thank you very much for your time and insight.

24

I work as tech support at a major internet reseller (we have a butterfly as our symbal). If the computer is not POSTing(Power On Self Test, when it counts your RAM and shows what CPU you have) it could be the Power Supply, Motherboard, CPU, RAM. If the fans are not spinning at all, it could be the Power Supply, Motherboard, or power switch.

To test the power switch, disconnect the power switch from the motherboard, and then take something metal, like the tip of a flat head screwdriver, and touch the two pins the power switch was plugged into together. The board should power up. If not then it is not the power switch.

To test the power supply, disconnect the power connectors from the motherboard, the 20pin power connector, and if you have it, the 4 pin power connector. Then on the large 20pin power connector, take a paperclip and short out the green wire to any of the blacks(If your system is a Dell, Compaq, Gateway, etc don’t do this, the wires could be a diffrent color) The power supply should power up, the fans on the power supply itself will spin, and you should be able to open your CDROM drives.

If these two did not work, you can try taking your motherboard out of the case and run it on a non conductive surface (wood, cardboard, basiclly anything without metal) in a minimal configuration (CPU, RAM, Video, Power) and try to turn it on. If it still doesn’t turn on it most likely is the motherboard.

Those steps I gave you are if the fans are not even turning, if the fans are turning then you need a diffrent set of steps to try.

25

That’d sure come in handy when it came time to fire her up now wouldn’t it?
Thank you for your help. It is appreciated.

This is handy Magiver type info.
Thanks, I’ll try it and remember it.

I’m still thinking about this one. I’m not so worried about the PSU as I am about me. Because I am so ignorant of how electricity behaves, I try not to put myself in a position where I need to know how it behaves.
I’m gonna hold out a bit for a plan B.
But on the other hand, smoking the PSU would give me a war story. Plus, it might be fun.

Nope, no fans for me.

Thank you for your time and advice.
I’m glad you took the time.

26

Don’t worry about the voltage from doing this, I don’t think there is any power in the green wire (or if there is, its VERY small), and the black wires are all ground. What you should do just to be on the safe side, is disconect the power supply from the wall when you do this, then hold the 20pin connector from the plastic, and plug it back in. That way you don’t even have to worry about getting a shock.

Your welcome, its just nice having an answer to a question on this board.

27

Well, I’ve laid everything out and tried to fire it up. Nada.

I skipped the shorting the PSU part because I had another known good PSU and I had already tried my PSU with another known good computer without success.
(As I am pretty sure that my PSU is shot, could someone tell me which wires to short to make it go boom as engineer_comp_geek mentioned?)

I tried the layout with my PSU first, then with the known good PSU.

Nothing but a lit LED telling me that the standby 5v was working both times.

Does this necesarily mean that my mobo’s shot?
Isn’t there someother option that doesn’t involve me dropping more cash for a mobo?

28

Ok, so we know now that
a) Your power supply is definitely bad (because you tried it in a working machine and it didn’t work)
b) Your power supply is not the only problem (because replacing it with a good power supply does not work either)
c) the processor is good (because it worked in another machine)

I assume the fans that are not turning (they’re still not turning, right?) are connected to the motherboard fan headers (i.e. the only wires the fan is connected to go straight to a 3-pin motherboard connector). This means that the mobo is also at fault, since it isn’t transferring power properly to the places it needs to go. If the motherboard worked and your processor/ram/video card was at fault, you would get some sort of beeping sound from the system (as well as fan activity) that would help diagnose the problem (unless your speaker is broken too). So now we know that:

d) your motherboard is broken.

Your RAM/Video card could also be broken, but we have no way of telling with the current mobo (since it’s broken). If you put them in a working computer and they work, you can feel fairly certain that those components are okay.

Yes, I mentioned it before, it’s an RMA. Since your motherboard is <6 months old, it is probably still under warranty. An RMA is where you send the defective product back to the manufacturer and they send you a new one. To get an RMA, you will have to call the motherboard manufacturer’s tech support number (generally found in your motherboard manual, or if you tell us what brand/model motherboard you have i’m sure someone can dig it up online). They will probably have you run a few tests similar to what we’ve suggested, and then give you an RMA # and a shipping address. Then you pack it up and ship the motherboard back to the manufacturer, putting the RMA number on several sides of the box for easy identification at their end, and they send you a replacement. The only cost to you will be the cost of shipping the defective motherboard to them.

You might also be able to RMA (yes, it is common to use it as a verb) the power supply if it has a warranty, otherwise you might have to buy a new one, which can run anywhere from $30-$60 depending on what brand and model you pick out.

As for learning to use a multimeter, you should be able to find a little basic electronics instruction online through google. If not, i’ll take a look online tonight and see if i can’t come up with a good site for beginners (if someone else doesn’t beat me to it).

If you want to make the old power supply go boom with a multimeter, you’ll run a risk of breaking the multimeter as well. If you really want to make the power supply smoke, squirting a little water into it through one of the ventilation holes before plugging it in will be sure to cause a failure, though it’s not a particularly safe (or smart) thing to do. Also this might void any sort of warranty on it, so you might want to check and see whether it can be returned first, and consider destructive options only after you’re sure it’s not salvageable.

[ot]On preview: I seem to have a weird fascination with parentheses lately, don’t I?[/ot]

29

Ouch! I’m not done with the denial stage of my grief.

I did forget to attach the video card :smack: when I ran the tests. I also did not reconnect the speaker to the mobo, :smack: so I have no idea if there were any beeps
However, neither fan budged.
I’ll run the tests again tomorrow when I can access the working power supply again.

I think I may be able to do this. I’ll have to check the Radeon site and see what the specs are. (We’re travelling and I left the documentation for it 500 miles away) and compare them to those of the working mobo at my disposal.

But damn, if I end up having to rebuild my whole computer I’ll sure want to know what was the root cause. I’d like to have a computer that I can’t afford to rebuild twice a year.

I know, I know but it was just the bargaining phase of grief speaking.

This would be smarter than blowing it up.

I googled bit earlier. I think I’m going to get a multimeter and once I get my computer back up, (and thus have a spare for experiments) I’ll google more earnestly and/or check back here to see what’s been reccomended.
Thank you very much and again for your help.

Og Bless the Dope! This thread alone (not to mention my computer conundrum thread of only last week (someone else’s computer)) was worth the price of admission. Thanks all.

30

From the sound of it, it’s just your motherboard/power supply, so don’t worry too much. :slight_smile:

An RMA is not the end of the world. Remember, it costs you only the price of shipping, and you get a working motherboard. It isn’t like the one you have right now is working properly anyway, so you’re not really missing out on much while it’s gone. Plus, some companies will cross-ship so you get the replacement sooner.

Basic Electronics.com
HowStuffWorks.com
doctronics.com - using a multimeter
acmehowto - how to use a multimeter

No problem, anytime.

31

Guess what.
Denial wins out yet again.
My mobo’s not toasted.
My power supply is still a paperweight though.

The jumper used to clear the CMOS had somehow disappeared. Once I stuck another one on there everything worked like normal.

I guess that somehow when I was examining my machine I must have knocked the jumper off.

I still need to get a new PSU and possibly I’ll pick up a USP.
Thanks again everybody.

I hope that this thread helps someone else in the future.

archival bait:
motherboard