12v reads 7v --5v reads 3v. This to me is not normal. The test was done with MB hooked up cause that was the only way turn on the supply. Is it the supply or MB that is the problem ?
It's the power supply.
Because it's made with cheap components for one.
The gauge of the wiring inside is too small.
The Electrolytic Capacitors are cheap. Have a bad formula for the Electrolytic paste inside.
The Rectifier Bridge is inferior.
I could go on, and on.
What has transpired is that one or more Electrolytic Capacitors inside have failed, or are failing.
This makes a weak voltage rail.
Electrolytic Capacitors inside a personal computer power supply are Filters. They are used to filter the incoming AC voltage in the Input stage, and the rectified, (DC) voltage in the Output stage.
An Electrolytic Capacitor resembles a small aluminum can. It has two leads coming out of the bottom. (The ones used for personal computers, that is)
Inside the Electrolytic Capacitor are three layers.
One layer of a strip of thin metal.
This is the Conducting strip, or Positive strip. Connects to the Positive lead. (Only the Negative lead is marked)
One layer of thin metal with a non-conductive coating applied to it.
This is the Non-conducting strip, or Negative strip. Connects to the Negative lead.
There is a strip of paper which is soaked in Electrolytic paste.
The strip of paper is laid in-between the conducting strip, and the non-conducting strip, then the all three layers are rolled up, and inserted into the 'Can'.
When an Electrolytic Capacitor goes bad, the paste forms a gas. Hydrogen Gas. This gas in turn creates pressure, and compromises the seals of the Can.
There is a rubber round seal on the bottom. There is a seal on top. The top of the 'Can' has a notch etched in it. Common shapes are an X or lK.
When too much pressure develops inside, the seal is pushed out of the bottom, (Slightly), and/or the notch on top of the Can splits open. In time Electrolytic paste oozes out.
So much paste loss, and the capacitor operates at a lower capacitance. Too much paste loss, and the capacitor fails.
(Also after time Electrolytic paste breaks down. Chemical reaction breaks the paste down. Designers are aware of this, and incorporate capacitors that are 50 percent better than is needed)
This is NOT an invite to open your power supply!
Capacitors are designed to slowly build up a charge, then release it all at once!
They can hold a charge for weeks, sometimes months! (Sometimes longer than this)
Should you reach inside, and touch your fingertips to the two terminals of a capacitor, it can release it's charge to you!
Should you reach inside, and your fingertips complete a circuit, that one or more capacitors are in, it/they can release their charge to you!
The best way is to use a power supply that is KNOWN to be good, and connect it for a test.
Computer power supply's put out three voltages. Two you have observed.
A.3.3 Volts (Orange insulation on the wire)
B.5 Volts (Red insulation)
C.12 Volts (Yellow insulation)
(Newer computers are doing away with the 3.3 Voltage Rail. Your power supply still has the 3.3 voltage rail)
As long as you have the correct power supply cables, and connectors, plus the right amount needed, you could use ANY power supply that puts out 160 Watts.
PROBLEM IS, the size, and shape of your power supply. You need one that is that size, and shape.
It SHOULD fit inside. Sitting outside the computer is a bad safety factor.
Therefore, it is my suggestion that you buy the correct power supply to fit your computer.
Bad motherboard? Don't think so.
Because of the voltage readings you have.
Do you see any bad Electrolytic Capacitors on the motherboard? Any that show visual signs of failure? This is the first hardware indication of a bad motherboard.
This gives more information on the visual signs of capacitor failure,
Also keep the inside of your computer clean, and the power supply. Computer unplugged from power, use a can of compressed air for computers.
When the inside of a computer, and it's power supply are dirty, the power supply has to deliver more power.
Heat = Wasted Energy.
The processor fan, and heatsink are dirty? Then the processor heats up, and requires more power. (Eventually the thermal limit of the processor is reached, and BIOS turns the processor off. It's a Fail Safe feature built-in. Keeps the processor from burning up)
The inside of the power supply is dirty, and it's fan?
Inside the power supply are heatsinks. They resemble the heatsink used for the processor.
A Heatsink draws heat away from the object it is attached to. Then air is drawn over the heatsink fins,( that are radiating heat), and heat is pushed away by the air.
The fan for the power supply draws air. Draws air into the power supply though the computer case. Once the fan blades, it's center hub, and the outside cage around the fan, become coated with dust/dirt, the cooling capacity drops tremendously.
The power supply has to keep up with the energy that is being wasted, and puts out more power.
Eventually components inside the power supply fail. (Electrolytic Capacitors are Generally the first to go)
Again, heat = wasted energy
Nov 22, 2009 |
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