Posted 21 May 2010 - 12:32 AM
HI and again welcome to Bleepingcomputer!
I would check that power on switch for a stuck button, your powering on, but if it remains in, it can put it in sleep mode, then off mode if the motherboard supports it.
You can check the switch with a VOM meter set to the Ohms mode, which simply passes one side of the meters battery through the probes looking for a closed circuit, if both probes in the Ohms mode are touched together, the circuit is closed and the meter is activated and registers continuity.
The same goes when testing a momentary switch, normally the switch is an open circuit, no current passes through it.
Once the switch is pressed, it closes the circuit and allows a current to flow across it. The meter will read a measurement, until it is released, then the circuit is now an open circuit, no current flows.
If you do not have an VOM multimeter, a simple 1.5 volt battery and a flashlight bulb can be used, simply connect one wire from switch to PLUS (+) side of battery, put bulb's metal shield on NEGATIVE (-) side of battery, then put other wire from switch on bulbs point (the tip) and have someone press the switch, the light bulb should light, release switch button, light should go off.
Some switches on computers come with confusing wire harnesses or ribbon wires which connect to various LEDs and other switch's, in this case you need to isolate the two wires that lead to the power on switch from the rest.
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