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 Post subject: Fun with Electricity
PostPosted: Thu Dec 12, 2002 7:04 am 
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Joined: Thu Dec 12, 2002 6:46 am
Posts: 6
Location: VA
Howdy all...

Just a funny story to share about trying to complete one of the mods (the 12v/5v switch)...

Yesterday, I read up on it got all excited and ran down to radio shack, they had the exact DPDT switch SPCR used... i crabed a few wires to complete the mode while i was there too.. Got home, broke out the soldering iron, heated up and went to work. 30 minutes later I was all set, proud of my work. I tested it.. It worked great! At first I had thought the 5v side didnt work, but the fan was just too quiet to hear! So, i decided to take it a step further and mount the swithcin the front of my case... I drilled thw hole, got it mounted and snapped the front of the case back on. I turned the computer on... and two of the wires caught fire! smoke everywhere... i scambled to unplg the comptuer... it was crazy!! Well, the project went down the drain, I assume two ot the contacts must have touched or somthing.. and the wires shorted out.

I'll be trying it again after I learn to solder better.

The project would have been great had I not been so careless... Anyone have any tips on soldering? Thanks for the great website!


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 Post subject:
PostPosted: Thu Dec 12, 2002 7:36 am 
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SPCR Reviewer

Joined: Sun Aug 11, 2002 3:26 pm
Posts: 3998
Location: Phoenix, AZ
This isn't exactly a soldering tip, but next time be sure to cover any exposed contacts with heatshrink, or even tape. It could avoid a repeat of your fireworks.

Is everything else in your system ok though?

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 Post subject:
PostPosted: Thu Dec 12, 2002 8:46 am 
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Joined: Thu Dec 12, 2002 6:46 am
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Location: VA
odly enough, i tried to get waht i thought was heat srhink at radio shack, but the 14 year old obviously hadnt seen an exposed wire before let alone know what heatshrink was....


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 Post subject:
PostPosted: Thu Dec 12, 2002 9:37 am 
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Joined: Sun Aug 11, 2002 3:26 pm
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Location: Vancouver, BC, Canada
Now that you've inhaled a whiff of burning plastic wire insulation, you're hooked for like, you'll never be able to leave your PC alone or leave this website for more than a few hours without getting the shakes... :twisted: bwahahahahah!

Um, seriously, maybe a bigger caution should be added on that project page. I've never read about anyone doing that with 12/5 project before. I personally have had a 4-pin power extension (for peripherals) burn and melt -- even the plugs! -- in my hands with sheer carelessness. Had criss-cross scars on my palms for ages.


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 Post subject:
PostPosted: Thu Dec 12, 2002 9:41 am 
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Joined: Thu Dec 12, 2002 6:46 am
Posts: 6
Location: VA
Yeah, I'm going to buy another switch today and try it out:)


I think anyone one even a small amount of sense would know the risks of playing with wires and what to do if ti starts smoking (unplug it).. but maybe a caution to be able to shut power off to the computer very quikcly would be in order just for maybe the younger ones who are playing winthout supervision.


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 Post subject:
PostPosted: Thu Dec 12, 2002 4:47 pm 
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Joined: Thu Nov 28, 2002 5:07 pm
Posts: 809
Location: London, UK
Hello,

Why not take it the safe way and just buy either a Zalman fanmate which can adjust from 5v to 11v for 3pin power connectors found on your motherboard which I guess cost slightlty less than $10 in the US. Or buy the Zalman multiconnector which plugs into a standard 4-pin molex connector and gives you two 5v and two 12v connections (3 pins). In the UK this cost a mere £3 so I guess in the US you get it for about $3, not much since you only need to buy just one.


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 Post subject:
PostPosted: Thu Dec 12, 2002 6:21 pm 
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Joined: Thu Dec 12, 2002 6:46 am
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Location: VA
...because there is already a hole drilled in the front of my case for the switch :D

if i hadnt already drilled the hole i might have considered...


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 Post subject:
PostPosted: Thu Dec 12, 2002 6:33 pm 
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Joined: Sun Sep 29, 2002 9:05 pm
Posts: 228
Location: Powell River, BC, Canada
Sorry to ask a dumb question, but are you sure the problem wasn't when you put the bezzel back on? Maybe the open joints on the back of the switch hit the case. Is there a burn on the metal case in behind the plastic? If the short was to the case, then you might not need a new switch. Which wires burnt, the 5 and the 12 (red & yellow), or was a ground (black) burnt? If no ground wires were involved then shorting to the case, or a short from 5 to 12 is indicated.

Anyways, good luck. And remember that even a huck of cardboard taped to the metal case behind the switch would prevent further mishaps of the case shorting kind.


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 Post subject:
PostPosted: Fri Dec 13, 2002 2:26 am 
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Joined: Sun Aug 11, 2002 3:26 pm
Posts: 333
Location: Melbourne, Australia
if u're not confindent of soldering u could always crimp the wires togther, lot easier to do, and a bit safer unless you're exposing the wires to a lot force to it...
heatshrink is defintely the way, u could also get paint on electrical tape :)

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 Post subject:
PostPosted: Fri Dec 13, 2002 3:26 am 
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Joined: Thu Dec 12, 2002 6:46 am
Posts: 6
Location: VA
crisspy wrote:
Maybe the open joints on the back of the switch hit the case. Is there a burn on the metal case in behind the plastic?

Could have been, I'm not really sure, I didnt see a burn on the case though.
crisspy wrote:
If no ground wires were involved then shorting to the case, or a short from 5 to 12 is indicated.

The two wires going to the fan were the ones that melted, the wires from the power supply were great. I need a new swtich because I'm having trouble getting the soldering off the bottom of the switch

Thanks for all the help guys... what a warm welcome to the site :D I'll be picking up the heat srhink and a new switch this weekend and trying it again, I'll tell you how it goes...


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 Post subject:
PostPosted: Fri Dec 13, 2002 5:31 am 
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Location: Powell River, BC, Canada
tollgate6 wrote:
The two wires going to the fan were the ones that melted, the wires from the power supply were great.


Ok, I am really scratching my head over this one now. I have done a lot of DC troubleshooting. I do solar electrical, and automotive electrical, as offshoots of being a general tech and machine head (now if I was only making real money at it). I have seen a lot of burnt circuits (no, electrical ones you smartass). Here are the steps that are going through my head:
  • Electricity only flows in complete circuits. Loops so to speak. Like from +12 or +5, through wires, then components that limit it, to 0v, then more wires, and back to the transformer in the PSU.
  • In a 7v circuit, the juice flows from +12, through wires, through the load, back to +5, for a net of +7v. Still a loop, we just moved 0v up by 5v as far as the load is concerned.
  • In any short circuit, you have an accidental contact forming a new, unintended loop. From +12 to +5 or 0v(including the whole case), or +5 to 0v.
  • In any short circuit, unless a fuse or breaker blows, or something else goes 'right', the weakest link in the loop-circuit gets damaged. If it's a short to the case, you can bet the whole case won't melt, so it will be a wire. The skinniest wire that is. Often a trace on a circuit board, or sometimes a weak-link component elsewhere.
  • If the leads to your fan are melted, then there has been a current loop through the fan that is big enough to burn the wires. OUCH. The fan is supposed to only let a small amount of current through. If it was a big fan that let more current through, it would have bigger wires.
  • So.... you must have had one of these problems:
    1. You had a chaife in the fan wire insulation én-route the fan. The wires shorted together, and will be burnt back from that point to the switch, but not all the way to the fan. The fan is ok, but it's wires died the flambé. Also check for a sharp edge cutting into the wires, one or both.
    2. One of the fan wires chaifed and shorted to 0v/ground (likely a case edge). On 7v, the fan has two + wires going to it (5 & 12), realative to 0v/ground, so either one could short out to 0v/ground. Only one of the wires is actually burnt.
    3. The fan is dead, shorted out inside. Both fan wires will be burnt all the way into the fan.
    4. Please no... The fan has RPM sensing, and that wire is burnt too. This would indicate, god forbid, a very unhappy fan that dies on 7v by shorting out through the RPM lead. Please let us know exacltly what type of fan this was. If this happened then your motherboard could have been damaged if the RPM lead was plugged in properly at the time. If it was accidentally hooked to some other power lead then that might have caused the problem (speculation).


Any which way I slice it, the problem is almost certainly well down stream from your nifty switch, which seems unlikely to be the problem. I can't think of any other way for the fan leads to be invloved. Please do let us know more about what happened.

Best of luck :cry:


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 Post subject:
PostPosted: Fri Dec 13, 2002 2:16 pm 
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Joined: Thu Dec 12, 2002 6:46 am
Posts: 6
Location: VA
okay, let me go into detail about how my fans was set up.

I bought a three posistion DPDT switch from radioshack and soldered a three prong tail onto the the switch. I soldred the 5 volt contacts on one end, and the 12 volts contacts on the other.

The three pring tail was then plugged into a three pring rpm sensing fan, but the rpm sensing wire was not hooked up toanything (could this be a problem?)

The tail i used, had previously broken, so i had to solder the wires to the plug, I was careful to look at another tail like it to get the right wire in the right posistion.

Also, a thing to note was when I snapped ont he bezel, the contacts on the switch probably came in contact with the case. (!?!?!)

One thing about the switch... Is there a correct side to put the ground on, I was under the impressions taht as long as you put all three grounds to the same side and all three wires with current to the other id be covered.

does that help any?


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 Post subject:
PostPosted: Fri Dec 13, 2002 9:52 pm 
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Posts: 228
Location: Powell River, BC, Canada
Quote:
The three pring tail was then plugged into a three pring rpm sensing fan, but the rpm sensing wire was not hooked up toanything (could this be a problem?)

No problem. Maybe good in fact, if the fan went too haywire, there was no possible risk to the mobo.

Please give me a detialed description of how the fan leads were burnt. Were both leads actually burnt? Only one? How far along towards the fan? I have seen when wires run along close together where one of them actually burns, and manages to melt ones nearby, but you can still tell that only one wire really burnt for its whole length and the rest are collateral damage. Also, I would have expected that if the short was actually at the switch, then the much heavier (than fan wires) PSU wires would have burnt, or been such a big short circuit that the PSU would have fried. As it stands, it seems that the small fan wires acted gracefully as an unintended but much appreciated fuse :) So your PSU lives on to volt anther day, and the wires to it (a pain to replace) are even still happy.


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 Post subject:
PostPosted: Sun Dec 15, 2002 3:03 pm 
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Joined: Sat Nov 09, 2002 4:03 pm
Posts: 1
I did a similar thing recently hooking a Hardcano 5 up, (pile 'o' crap btw) the 12v feed to the speed control got caught on one of the MANY sharp edges and shorted out. God damn a TruePower 550w can throw out some current when it wants to :shock: :shock: :shock:
There is now a nice large black mark on the inside of the Hardcano housing 8)


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