Ahh, the smell of burnt circuitry

[Merkuri]

So, a couple of weeks ago I posted about some computer problems I was having. I eventually broke down and got a new computer, which seems to be working fine. My new problem is with the old computer.

This may be a long story, but I don't know what details are necessary, so I'm including all I can remember about the problem. Please bear with me.

Now, I had no doubts when I bought a new computer that I could get my old one working with enough elbow grease and reformatting, but I figured that if I was going to go through all of that I would rather throw out the really old PC in our living room acting as a DVR (for those who don't know what a DVR is, think "homemade Tivo") and use the recently-replaced one as the new DVR.

So that was the plan for the old computer. My boyfriend, Awayfarer, expressed interest in the memory it had (it had 2 GB of RAM... don't remember how much he had, but it was less) so today we decided to swap RAM sticks before the old computer started its new job. I was fairly certain we had already done this once before (I tend to upgrade my PC first and give him the pieces I'm replacing), so I had no worries about memory compatibility.

The sticks came out of my machine fine and went into Away's machine with only a little bit of pushing (which he said he remembered having to do the last time he replaced the memory). His box booted up just fine and recognized the new RAM.

My machine was another story. The first memory stick I put in took a little pushing, just like when I put my sticks into Away's box, but the second stick just did not want to go. It seemed like it was just a millimeter or two too long for the slot. I thought I must be imagining it, since it seemed exactly the same length as the other one that went in. I kept trying to put it in longer than I should have, and eventually a piece of the plastic memory holder on the motherboard broke off. There was no circuitry on the piece that came off, so I figured it wasn't essential to the performance of the computer. Since the machine was just going to be used as a DVR I figured one stick of memory would probably be enough, so I put the second stick aside, closed the box up, and tried to start it.

Now, when I had swapped this older PC for my new one I had just unplugged all of the cables from the old PC, moved the physical box aside, put the new box in its place, and plugged all the cables back in. This includes the power cord, so the brand new PC was using the power cable that came with the old PC. The new power cord for the new PC was still wrapped in plastic in a box somewhere, unopened. When I tried to start my old PC after replacing the memory I pulled out the brand new power cord and plugged the old PC in with that. So the new PC was using the old cord and vice versa. I didn't think twice about this because as far as I know all of these cords are identical.

When I tried to start the old PC the lights flickered on the front like it was starting, then went black. I tried to hit the power button again and nothing happened. I figured it was a problem with the memory and decided to deal with it later (though I did think it was odd that it refused to power on instead of powering on and giving a beep code or something like that), so I left the machine as it was and went back to play with my new box.

Some time later (not sure exactly how long, but I'd guess somewhere between a half-hour and two hours) I heard an electrical-sounding series of pops and crackles. I rushed around to see that the old computer was slightly smoking. I unplugged it quickly, brought it outside, and opened it up. I saw no scorch marks anywhere. I felt around gently inside the machine for heat sources. Everything was cold except the power supply, and when I sniffed the power supply's fan I smelled smoke. Seemed pretty obvious to me that something bad had happened to my power supply, but I had no idea what or why. I have not tried to turn on or plug in that computer since.

What happened? Can anyone tell from reading this story what went wrong? Did the memory somehow cause a short in my power supply? Could they have sent me a power cable with crossed wiring? Or was it a mistake to use a new power cord with an old computer? If that's the case, should I not be using the new computer with the old power cable? On the chance that it's a bad power cable I don't want to use it on the new machine for fear of blowing its brand new power supply as well.

If it matters, my new machine is this barebones system with a few pieces added on (none of which I believe matter - nothing was taken out of the barebones, just added to it). My old machine is another barebones from Tiger Direct. I don't think there's a link still available to it because it's about four or five years old now. I believe it had a 300 W power supply. My boyfriend's computer (where I got the memory that wouldn't fit) is a Dell Dimension 3000. At some point he replaced one or both memory sticks. I don't remember what their sizes are, but I know that they were not matching (I think they might have been one 512 MB and one 256 MB). I don't know which one ended up in my machine. (The one sitting on my desk doesn't have a size written on it that I can see.)

Any ideas? Do you think my old machine is salvageable if I get a new power supply?

 

[dvvega]

Unfortunately from my experience with hardware, forcing any of it is a bad thing. You should never have to force memory into its slots, no matter what kind of machine you are using. I've never had to and I've changed a lot of memory in my time (used to work tech support for Parliament House here in Sydney).

The fact that you forced memory hard enough to break off something (a plastic bit), indicates you most likely broke the locking piece on the memory slot. This little piece of plastic is the "click" you hear when you put your memory in. That technically is not an issue.

However - there are a couple of things that may have happened besides just a little bit of plastic coming off.

1. You may have actually broken a little more than you realise, thus creating a little short circuit in the memory section, thus overloading the motherboard (very rare, but still doable).

2. Your old computer's power supply was ready to give up its life anyway, and it is just a coincidence that it happened at this time.

3. The memory was indeed the wrong type for you machine and this was the magic stick that decided that it had had enough and "boom".

Now I doubt it is the cable. Cables in and of themselves do not carry any power in them. You may have received a surge at the "right time" to coincide with plugging it in, however you stated it was a while before it went snap, crackle, pop. This could mean your power point overloaded somehow ... do you have it sharing output? Maybe one of those 4-ways?

Perhaps you didn't place the cable into the power supply fully, leaving it half-in/out ... this can cause a short circuit.

Is the new cable a non-earth cable? Whereas your older cable was an earth variety? If so you are lucky you kept the old one for the new machine.

Hopefully those points lead you to investigate further or at least eliminate something from your "what ifs".

D

 

[Merkuri]

Unfortunately from my experience with hardware, forcing any of it is a bad thing. You should never have to force memory into its slots, no matter what kind of machine you are using. I've never had to and I've changed a lot of memory in my time (used to work tech support for Parliament House here in Sydney).

Yeah, I know. In my defense, I usually have to push pretty hard to get memory in. It never just slides in like I feel like it should. And in this case I just couldn't believe that it would be too large for the slot, especially since there was a good chance that this memory actually came from my computer in the first place. Like I said earlier, I am pretty sure I upgraded this machine's memory in the past and gave its original memory to my boyfriend. I thought I was just taking my memory back.

I just talked to Awayfarer, who says that one of the sticks was original to the machine and the other was an addition, probably from my machine when I upgraded. I'm guessing the one that fit was "going home" and the one that didn't fit was the original spawn-of-Satan Dell memory. Stupid Dell and their nonstandard parts. I bet they made it a millimeter too large on purpose. Still my fault for trying to force it.

The fact that you forced memory hard enough to break off something (a plastic bit), indicates you most likely broke the locking piece on the memory slot. This little piece of plastic is the "click" you hear when you put your memory in. That technically is not an issue.

Yes, that's definitely what broke off. I have the little white locking lever still attached to some purple plastic from the slot itself. I figured I could actually have put the memory in now that one end of the slot was gone but at that point I decided should stop since I had done enough damage (though apparently not, since smoke was in my future).

3. The memory was indeed the wrong type for you machine and this was the magic stick that decided that it had had enough and "boom".

While I agree that's possible, why is my boyfriend's computer running wonderfully? If my memory worked in his, shouldn't his memory work in mine?

Now I doubt it is the cable. Cables in and of themselves do not carry any power in them. You may have received a surge at the "right time" to coincide with plugging it in, however you stated it was a while before it went snap, crackle, pop. This could mean your power point overloaded somehow ... do you have it sharing output? Maybe one of those 4-ways?

It was plugged into a surge protector that's fairly new (bought it between 6 months and a year ago) along with the other computer and a few other electronic pieces (stereo, printer). It's pretty full, but nothing else plugged into the surge protector is having problems. If it was a surge that somehow got past the protector I would've expected both computers to smoke.

I know that the cable itself has no power, but could this have happened if the negative and positive lines in the cable got crossed when it was manufactured? So the power supply got negative current where it was expecting positive and vice versa? After it was done smoking and I had some time to think about it that was one of the theories I came up with. Does that type of thing ever happen? Is there any way I can (safely) test the polarity of a power cable? Preferably without buying expensive equipment.

Perhaps you didn't place the cable into the power supply fully, leaving it half-in/out ... this can cause a short circuit.

While that's a possibility, I doubt it. It looked fully seated when I yanked it out after seeing smoke.

Is the new cable a non-earth cable? Whereas your older cable was an earth variety? If so you are lucky you kept the old one for the new machine.

What's the difference? Both cables looked exactly the same except one was shiny black and new and the other looked a bit duller and older. They both had the third prong for the ground, if that's what you're asking.

I'm guessing that my existing power supply is definitely dead and I shouldn't even try to plug it in again. Do you think it would be worth it to buy another power supply and see if that makes it work, or is there a good chance I'll fry that one, too? I'd like to get that machine up and running to replace the DVR in the living room, but I don't want to spend money on a power supply just to kill it right away.

 

[dvvega]

Just blame your boyfriend ... it is all his fault

As to why is his machine still working and yours not? Just dumb luck for you.

The third prong is what I was talking about on the power cables. That is the earthing prong. And the fact you used a surge protector discounts the cable being at fault.

So that leaves the power supply as being the weak point or the memory. Now the issue to test this is if the power supply caused the problem or the memory things caused it.

Unfortunately you cannot test this without risking another power supply. Your theory of cross-cabling is pretty non-valid ... the reason for this is that it would also require the power supply to not be "normal" since your previous supply was okay (in the old DVR system).

So you have the following choices to test what is wrong ... get an old, but working, power supply and put it into "Mr Explody" and see what happens. If it happens again then it is the memory at fault and what happened when you pushed it. If nothing goes wrong then it was your supply just giving up its life.

The other option (to risking a supply) is to get the old one checked by a repair guy.

D

 

[Merkuri]

Just blame your boyfriend ... it is all his fault

I did.

Your theory of cross-cabling is pretty non-valid ... the reason for this is that it would also require the power supply to not be "normal" since your previous supply was okay (in the old DVR system).

I was thinking that the crossed cable was an accident somehow, not something intentionally built into the cable. The first time I used that cable for anything was on the old PC when it fried. I had literally just taken it out of the box and the plastic wrapper. This is why I was thinking its construction might be somehow flawed.

And the power supply in the old DVR system isn't part of this equation at all. I haven't touched that machine, and I only mentioned it because I wanted to replace it with the one that fried.

Basically, there are these four machines involved in my story:

• New PC: The brand new PC I just bought that is now plugged in with the cable from the old PC. This appears to be working fine (except for a few minor "growing pains" that I think are related to the fact that it's having to download and install huge chunks of Windows Updates).
• Old PC: The PC I'm replacing with the new PC. This is the one that fried when I put in memory from Away's PC and used the cable from the new PC (which had never been used previously, not even on the new PC)
• DVR PC: The PC in my living room being used as a DVR. It's even older than the old PC and was not touched during this whole fiasco.
• Away's PC: My boyfriend's PC that now has the memory from the old PC and is working fine.

The reason I suspected the cable is that the one time it had been used was when the machine fried.

I'm tempted to unplug the working machine and plug it in with the new cable to see if it works. I was thinking I might plug it in and unplug it immediately if it shows any problems turning on, but even though it took my old PC a few minutes/hours to start crackling it's possible that damage was done right away but it just didn't become obvious until it started smoking. I don't want to risk any harm to the new machine, though. I suppose I could test it out with the older DVR PC, but it seems a shame to risk harm to a perfectly good machine, especially when I don't have a working box to replace it with at the moment.

 

[dvvega]

Now that you supplied a little extra information ... I wouldn't be testing the new PC with the new cable ... just in case it is the cable. There is another option and that is to test the old DVR machine with the new cable. If the old machine goes "pop" then its the cable and you are so lucky you didn't put it into your new machine.

You might want to take the cable back to the point of sale and mention what happened to them.

D

 

[Merkuri]

You might want to take the cable back to the point of sale and mention what happened to them.

I bought the machine online, unfortunately. Maybe I'll send their customer service department an email and see what they say. If they're cooperative maybe I could get them to send me a new power supply free of charge.

My boyfriend has an old computer that he doesn't use. Maybe I'll test the power cord with that instead of the DVR machine, if he's willing. This is his fault, after all.

 

[LightPhoenix]

It sounds like the power supply blew, and shorted the motherboard. I've seen this happen to a number of computers (including my desktop just a couple of weeks ago). I would of course test the power supply, RAM, BIOS, and processor first. However, the symptoms you describe - burning smell, refusing to power on - almost always in my experience resulted in the mobo needing to be replaced.

 

[Merkuri]

Aw, I'm hoping I won't need a new motherboard because that means I'll probably scrap the whole PC, which is a shame. I like putting my old PCs to work.

Is there anything visibly that could tell me whether the motherboard is fried? I saw no damage to the motherboard, and the smoke smell was definitely coming from the power supply and nothing else. I literally put my face right up to the computer's guts and sniffed around inside to try and find what had been smoking and the power supply was definitely the source.

By the way, both the place I bought it from and the manufacturer are being pricks and refusing to give me anything because the piece that broke was not from them, even though their product caused it. I'm really hoping it's just the power supply because it'll cost me less than $30 to replace. I can't see spending much more than that on a PC that's just going to be come a glorified VCR.

 

[Rackhir]

Is there anything visibly that could tell me whether the motherboard is fried? I saw no damage to the motherboard, and the smoke smell was definitely coming from the power supply and nothing else. I literally put my face right up to the computer's guts and sniffed around inside to try and find what had been smoking and the power supply was definitely the source.

Motherboards will usually have some sort of power lights on them, but if even if the problem isn't the power supply, it never hurts to have a spare power supply you can use in your new machine. Since they are one of the most likely to fail components.

It's highly likely that there will be no visible signs of damage to the motherboard even if there are. Also there can often be a cascade of problems. IE. bad power supply fries motherboard that fries memory which might fry the motherboard if put in a new machine. I would just junk the ram from the dead machine if it turns out that the problem is not just a dead power supply.