Blown a fuse in Desktop?

G

guy_1189

New Member
Oh hi guys,
First time poster here. What i've done is cut the -12V wire (purple) on my computer power supply and reconnected it so I can get a -12V feed for a mod I'm doing (finished doing). And now my computer won't start :mad:
I just asked the question on Yahoo answers and some guy said you should never cut the wires that go onto the 20 24 motherboard connector? Is this so? Anybody here can help me out? I think i've blown a fuse in the power supply.


Here is the mod : http://xoscope.sourceforge.net/hardware/hardware.html
 
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guy_1189 said:
Oh hi guys,
First time poster here. What i've done is cut the -12V wire (purple) on my computer power supply and reconnected it so I can get a -12V feed for a mod I'm doing (finished doing). And now my computer won't start :mad:
I just asked the question on Yahoo answers and some guy said you should never cut the wires that go onto the 20 24 motherboard connector? Is this so? Anybody here can help me out? I think i've blown a fuse in the power supply.


Here is the mod : http://xoscope.sourceforge.net/hardware/hardware.html
Click to expand...

A mod for what? You should never cut the cables!!! Not to the motherboard! Its like getting the power supply to your house and cutting it in half and putting a toaster in!

I do not understand the point in this:
buffback.gif
buffinst.gif

I dont know what this does but use the molex connectors if you need to dissasemble a cable! Not the motherboard plugs! :angry::eek:
 
EclipticShell said:
A mod for what? You should never cut the cables!!! Not to the motherboard! Its like getting the power supply to your house and cutting it in half and putting a toaster in!
Click to expand...

Thanks but I dont understand the analogy. Why should the cables to the motherboard never be cut?. The molex connectors have +5, GND, GND, +12. Of which I used 3. But I still needed a -12V which is why I tapped the (not purple:() Blue wire to the motherboard connector. I see now I've done something very wrong but I still dont understand how tapping a feed off here could effect anything at the motherboard.
 
guy_1189 said:
Thanks but I dont understand the analogy. Why should the cables to the motherboard never be cut?. The molex connectors have +5, GND, GND, +12. Of which I used 3. But I still needed a -12V which is why I tapped the (not purple:() Blue wire to the motherboard connector. I see now I've done something very wrong but I still dont understand how tapping a feed off here could effect anything at the motherboard.
Click to expand...

If you put anything into a circuit, the new accessory will always produce some resistance which will cut the ammount of current that the other components get. With things like lights, it is not much of a problem, but with motherboards, they do not have much tolorance to what would almost be like a brown out, not enough current. Its like saying if you have a AA battery with a light connected, it will glow, when you add two lights, they both will glow but slightly dimmer.

This is what I guess is happening.

All mobos can act differently remember.


As Spirit says: "don't mess with power supplies, they can hold a very dangerous charge for a long while and once you cut any cable and leave it exposed or disconnected the power supply will either be useless or dangerous."
 
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EclipticShell said:
As Spirit says: "don't mess with power supplies, they can hold a very dangerous charge for a long while and once you cut any cable and leave it exposed or disconnected the power supply will either be useless or dangerous."
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Yes but how else can you get -12 V out of your computer for a mod?? It must be a thing many people have done before. If this computer is f%$&$.. then no problem, I'll replace the fuse or the motherboard, but what I really need to know is how can you get -12V out of your computer ? I'm not worried about the voltage on the caps, I wont touch them :P
 
guy_1189 said:
Yes but how else can you get -12 V out of your computer for a mod?? It must be a thing many people have done before. If this computer is f%$&$.. then no problem, I'll replace the fuse or the motherboard, but what I really need to know is how can you get -12V out of your computer ? I'm not worried about the voltage on the caps, I wont touch them :P
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your 4 pin connectors provide 12v? http://en.wikipedia.org/wiki/Molex
http://www.societyofrobots.com/electronics_negative_voltages.shtml converts it into a negative voltage. I do not know much about this so forgive me!
 
EclipticShell said:
Anytime. Just wished you had asked the peeps here first, since you have probably now ruined your psu and mobo :(
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I think not. I must have grown a brain in my sleep becoz this morning I decided to take my disconnect my mod from the power supply, and, WHAMMO! - the computer works just fine:P. It just doesnt like my mod ! Now I think it may be a current drawing issure like you said.
 
guy_1189 said:
I think not. I must have grown a brain in my sleep becoz this morning I decided to take my disconnect my mod from the power supply, and, WHAMMO! - the computer works just fine:P. It just doesnt like my mod ! Now I think it may be a current drawing issure like you said.
Click to expand...

Well you know not to do it next time :P Hope I helped :)
 
Tapping into the -12V line of your power supply shouldn't be a problem. If you think about it, that's exactly what is happening once the connector is attached to the mobo, different components "tap" into the -12V for their needs.

However, if your new mod has an issue where it has a short or some other issue, it could definitely cause problems. Have you tested the mod outside the computer? Do you have a meter so that you can measure the current draw and voltage where you have tapped into the wire?

It could also be that your power supply is just too anemic to supply the power required for your mod AND what the mobo requires. If that's the case then a higher wattage PSU may work (ensure that it can supply more current on the -12V line).

Another possibility could be the way you physically attached to the PSU wire, if you didn't do a good job of soldering the connection ( or however you did it) it might be possible that you "broke" the connection of the -12V to the mobo. A meter would help you determine that as well.

BTW, you are safe working on the PSU as long as you don't open the metal case. None of the voltages coming out of a PSU are high enough to be an issue. However, within the metal housing of the PSU there are lethal voltages so don't ever open it unless you know what you're doing.
 
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