Computer Woes

[Drache]

Ok my grandma had a used computer set aside for her about 8 months ago. It was allot newer that the 8 year old compaq she's been using for ages now (still has windows ME on it). The newer computer (Vista) worked fine when it was shut down 8 months ago, in fact I was the one who shut it down.

Fast forward to today. I hooked it all up and pressed the power button on the tower, nothing, not a single beep, not a millimeter movement of a fan, nothing. I check the powerbar and it's still on, the switch on the back of the tower is still on, I'm just at a loss. This computer hasn't been plugged in and just sitting on a table in a spare room.

I had opened up the case and made sure EVERYTHING was properly connected.

On a whim I had popped out the CMOS battery for 10 minutes and then put it back in and the computer seemed to boot up fine. I turned it off so I could put it back where it was supposed to be and the damn thing refused to boot up again. So I took out the CMOS battery again. 5 minutes later I was across the room heard a VERY LOUD zap and saw SPARKS coming from inside the tower! The damn thing wasn't even plugged in!

I can't see any burnt wires or fried boards and there isn't even any sort of a burnt smell....

I think the power supply shorted out but I can't be sure.....

[DodgeByDave]

Check for a popped capacitor on the power supply, The Chinese are notorious for installing undervalued caps in power supply boards.

I have been making a good living here of recent repairing Magnavox/Phillips TV's, there is a 25v capacitor installed in the circuit where a 35v should be used

If you have one of these junk plasma TV's, it's the 25v capxon capacitor in slot #2074. Test with an ohm meter for continuity. The correct value capacitor can be purchased for 5 bucks at radio shack.

Also look for a bulged or completely burst outer case on all of the capacitors.

May not be the problem, just my 

[Khyron]

depends on how skilled you are with the inside of a computer. The system will have a ATX power supply, Test it. Don't be intimidated, do what I highlited in RED. I do this all the time.

http://www.duxcw.com/faq/ps/ps4.htm

Q.  How can I "trigger" an ATX power supply to test it?

A.  Do this at your own risk... 

Is the power cord plugged into the power supply? Is the surge protector on?
Is it plugged into a live outlet?   
Plug the power supply AC power cord directly into a wall outlet.   
Many recent ATX power supplies have an additional power switch on the back of the power supply itself.  Is it on?
Is the power supply set for the correct voltage?  Most of them have 110/220 Volt switch.  The 220 volt setting won't work in the U.S.A.  The 110 volt setting in Germany, for example, will probably fry the power supply--I've done it!
Unplug the power cable to the power supply and disconnect all of the power cables from the power supply except the main power connector to the motherboard.  Disconnect all other cables to the motherboard except the front panel power-on connector.  Remove all expansion boards from the computer.  Push the power-on switch and see if the power supply fan turns.
Try another outlet.


Now to answer the question... Unplug the power cord from the power supply, short-out pins 14 and 15 on the power supply main power connector, and plug-in the power cord just long enough to see if the fan is working.  This may not be the best thing to repeatedly do to an ATX power supply (it can damage it).  The ATX12V Power Supply Design Guide states that the power-on function should be normally done with TTL (transistor transistor logic) circuitry which pulls pin 14 low.  I use a jumper cable with alligator clips at each end with partially stretched-out paper clips in each alligator clip (an old trick).  Pull the power plug before removing the jumper.  If the power supply works, remove the motherboard and see if it is shorted-out by a stand-off or lose screw.  I have seen cases where a particular "good" ATX power supply would not work with a particular "good" motherboard--so much for standards and design guides.

[Drache]

depends on how skilled you are with the inside of a computer. The system will have a ATX power supply, Test it. Don't be intimidated, do what I highlited in RED. I do this all the time.

http://www.duxcw.com/faq/ps/ps4.htm

Q.  How can I "trigger" an ATX power supply to test it?

A.  Do this at your own risk... 

Is the power cord plugged into the power supply? Is the surge protector on?
Is it plugged into a live outlet?   
Plug the power supply AC power cord directly into a wall outlet.   
Many recent ATX power supplies have an additional power switch on the back of the power supply itself.  Is it on?
Is the power supply set for the correct voltage?  Most of them have 110/220 Volt switch.  The 220 volt setting won't work in the U.S.A.  The 110 volt setting in Germany, for example, will probably fry the power supply--I've done it!
Unplug the power cable to the power supply and disconnect all of the power cables from the power supply except the main power connector to the motherboard.  Disconnect all other cables to the motherboard except the front panel power-on connector.  Remove all expansion boards from the computer.  Push the power-on switch and see if the power supply fan turns.
Try another outlet.


Now to answer the question... Unplug the power cord from the power supply, short-out pins 14 and 15 on the power supply main power connector, and plug-in the power cord just long enough to see if the fan is working.  This may not be the best thing to repeatedly do to an ATX power supply (it can damage it).  The ATX12V Power Supply Design Guide states that the power-on function should be normally done with TTL (transistor transistor logic) circuitry which pulls pin 14 low.  I use a jumper cable with alligator clips at each end with partially stretched-out paper clips in each alligator clip (an old trick).  Pull the power plug before removing the jumper.  If the power supply works, remove the motherboard and see if it is shorted-out by a stand-off or lose screw.  I have seen cases where a particular "good" ATX power supply would not work with a particular "good" motherboard--so much for standards and design guides.

problem is that the computer wouldnt power on BEFORE the sparks, so what would shorting out the power supply accomplish?