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Power supply caused smoking cable


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#1 anonanon

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Posted 12 June 2015 - 09:29 PM

I have a desktop PC that gets light-duty use and is about 5 years old.  Yesterday, after being on for a half hour on a medium-warm day, it started giving off dense smoke.  We killed the power, opened it up, tried a restart, and discovered the problem  -- the power cable to the hard drive immediately started smoking again.  It had melted onto the HD at the connection.  Part of the power cable farther toward the power supply box was also blackened, though maybe just from smoke.

 

I tested the hard drive on a different PC and it seems to work fine.  So it seems obvious that the power supply or the power supply cable to the HD caused this problem, not the hard drive.  I'm about to replace the power supply and its set of cables with a new one and see if the PC works again.

 

A few questions:

 

1.  Anything wrong with what I'm planning to do -- just install a new power supply and see if the PC works okay?  Anything else I should do first?

 

2.  How rare is this kind of an power supply failure event?  In the past I've left a PC on when I'm not home, or overnight.  I'm thinking maybe that's not a good idea in the future.

 

3.  Is an event like that likely to generate enough heat to cause a larger fire, or likely to burn out inside the PC case?  Any experience?

 

4.  I'm planning to buy this power supply:

Corsair Builder Series CX 500 Watt ATX/EPS  80 PLUS (CX500)

 

Last year I used this model to replace a failing power supply (which was causing screen flicker, not smoking) in a different PC, which, perhaps not coincidentally, was custom built by the same shop as built yesterday's problem PC.  Any objections to this Corsair power supply?

 

5.  Is it reasonable to expect a power supply to last more than 5 years?  In my previous computers, they did, but I'm 0 for 2 with the last two PCs.  Should I plan on preventatively replacing power supplies in computers that pass the five-year-old mark?

 

I know that's a lot of questions; thanks for answers to any of them.

 

Roger



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#2 dicke

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Posted 12 June 2015 - 09:58 PM

A few answers

 

1. Sounds like a reasonable plan

 

2. I keep my system powered up at all times unless I'm going to be gone overnight, or longer.  The failure might be rare but then I haven't kept a power supply and cables in service for five years yet.

 

3. Any event that can generate smoke might also generate flame.

 

4. I don't know what you have in the way of hardware installed but I would do a power calculation before I made a final choice of the power supply. After making the calculation, add 20% for upgrading components. That figure should be no more than 75% of the rated value of the new poser supply. If you know you are going to add more 'stuff' you might even want to go a bit bigger. A power supply running above 80% of capacity can get very hot and cause problems for other components.

 

5. I can't comment on 'reasonable' as there are too many variables. A 5 year replacement cycle does seem reasonable.

 

All of the above is my personal opinion based on experience and having broken / fixed and built a number of systems for myself and others.

 

Dick


Edited by hamluis, 13 June 2015 - 04:37 PM.
Removed unnecessary quotebox - Hamluis.

Stay well and surf safe [stay protected]

Dick E


#3 mjd420nova

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Posted 13 June 2015 - 10:25 AM

Over the years, I've encountered many melted and fused connectors, hard drive ones being the most common.  The cause has always been a loose connection.  Whether from poor construction or from repeated plug and unplug action or just plain lack of proper seating during installation.  Replacing the P/S and any other connectors affected is needed. Sometimes, connectors or jumpers should be eliminated to direct wiring.



#4 anonanon

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Posted 21 June 2015 - 11:36 AM

Thanks for your replies.  I think the cable wasn't loose before it started smoking, so I'm still baffled as to why it did.

 

I've replaced the power supply with a 600 Watt Corsair.  There seems to be power to all components, including the CPU fan on the motherboard -- when I try to boot up, the hard drive light flickers, too.

 

But I get no output on the screen.  Nothing; it does not show me that it's starting to load anything; I can't go to BIOS and check the boot device priority.

 

Is there something else that could have been damaged during the smoking cable event, that I could test somehow?  So far I have considered only the power supply cable, the data cable (which looked fine), and the hard drive.  I replaced the power supply and the data cable.  And I have checked the hard drive by hooking it up to a different PC.  The hard drive initially would not boot (corrupted Windows folder -- it has Win XP Pro SP3).  After trying several reboots, the PC automatically did a chkdisk routine that repaired some things.  After that, the hard drive did boot successfully -- that is, it took me to a Windows screen asking me for the product key (evidently it was suspicious because it found this copy of Win XP on a different PC than in the past).  So I think the hard drive is okay; the PC should be able to boot from it.

 

Thanks for suggestions.

 

Roger



#5 dicke

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Posted 21 June 2015 - 02:53 PM

Roger,

If you are getting nothing on the monitor you may not have all of the cables from the power supply connected. In addition to the 24 pin connector there should be at least one other 4 or 6 pin connector which provides buss power to the GPU and other plug in cards.

 

Dick


Stay well and surf safe [stay protected]

Dick E


#6 technonymous

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Posted 21 June 2015 - 03:21 PM

Power supplies can deliver a lot of current on a 12 volt rail. Some of them power cables and molex can be utter garbage straight from the factory. Sometimes you get these strings of case lights running on Y with a thinner wire pigtail and with no inline fuse or resistor at the LED. They get really hot and melt and *poof* smoke and fire. As far as fire spreading is from the plastic front face on the case. That plastic is toxic as hell and flamable and goes up like a cannon fuse. Over the years I have seen a lot of crazy stuff. LIke a PSU with no rubber/plastic grommet to protect the wires from cutting or shorting to chassis. lol I guess the manufacturer desided a simple 50 cent molded piece of rubber cost to much. A lot of this electronical failure is due to very poor safety, quality control inspection from our freinds in China and other places. Then it ships right through customs and then burns your house down.



#7 anonanon

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Posted 21 June 2015 - 09:18 PM

Dear Dick,

 

I did make the other 4-pin connection to the motherboard, as well as the 24-pin connection.  And of course to the hard drive (power supply and data cable) and to each of two optical drives (power supply and data cable).

 

I have all three of those drives running on one of the power supply cables -- since it has three plugs spaced at appropriate intervals.  The hard drive seems to have power.

 

Is there anything else I should check?  Is it possible that something got damaged on the motherboard?  I can see no heat or smoke damage on it; such damage seemed to be limited to an inch or two near the part that melted.

 

Roger



#8 technonymous

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Posted 21 June 2015 - 09:52 PM

No video or post means dead cpu/motherboard or gpu or both or all the above. The only thing you can do is pull the bios battery out pull the power cord to psu replace them and pray it turns on. If you have a motherboard that has onboard video use it instead of the PCIE and see if video returns or vice versa. Also, be aware a bad cpu or motherboard can blow out a new one. A shop can determine with diagnostic devices to see which is bad. They are pretty much throw away electronics unless a shop can do the repairs and it's priced right.



#9 dicke

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Posted 22 June 2015 - 06:50 AM

Roger,

If you can test the GPU and CPU in another system do it. Pulling the CMOS battery to allow that device to reset might also help. Motherboard damage may not be visible. If all of the pieces work and you still have no system - it's the motherboard. Sorry :(

 

Dick


Stay well and surf safe [stay protected]

Dick E


#10 anonanon

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Posted 27 June 2015 - 03:05 PM

Thanks for all your suggestions.  The tips about the GPU led me to remember that this PC has two video outputs, one on the motherboard and a separate card.  I had the monitor plugged into the wrong one before.  Now it works fine.

 

Roger



#11 dicke

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Posted 27 June 2015 - 07:07 PM

Roger,

Glad all is well.

We'll be here when you need us

Til then

Stay well and surf safe

 

Dick


Stay well and surf safe [stay protected]

Dick E


#12 merkez

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Posted 29 June 2015 - 10:48 AM

Roger, nothing is wrong with the plan except that you can use a power supply with built-in fuses so that the fuse blows out instead of the wire burning. Just in case you want to be extra safe, attach a fuse to the power connections going to your HDD and GPU if you have one so that whenever they start sinking more current than necessary, they fuse blows out and you can have a look at what when wrong.

 

Regards,

O. Merkez

http://blog.7pcb.com/






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