CPU fan runs, harddrive picks up, but no display.1) Bad Power SupplyOr2) Bad graphics chipset.The two main factors for desktop computer failure, is a bad power supply, and/or the computer is dirty inside.A) Bad Power SupplyWeak voltage power railEnough power to light LED lights, and perhaps spin fans, but not enough power to turn the Processor on.IF all of the LED lights were on at once, they would use less than 1 Watt of power.EACH fan uses 2 to 3 WattsA typical Processor can use from 51 to 125 Watts. Just depends on what Processor it is, as to what the maximum Wattage usage is.CPU fan runs? Sure. It's only using 2 to 3 Watts.Harddrive 'picks up'? You will hear the Spindle Motor spinning the Platters inside. Means nothing. With no Processor running, BIOS can not hand the computer over to the Operating System. (WinXP is one example of an O/S)There is nothing to find the Boot Record, on one of those Platters inside the harddrive.(Explanation of physical construction of an average Harddrive,
http://computer.howstuffworks.com/hard-disk.htm )You can check the Power Supply voltages out. See if there is a weak voltage power rail. Power coming into the Power Supply is the dangerous voltage.Power coming out of the Power Supply is not. The Power Supply in your Personal Computer is an SMPS.Switched-Mode Power Supply,
http://en.wikipedia.org/wiki/Switched-mode_power_supplyYour Power Supply converts the electricity from your home, or business, into three main voltages,A) 3.3 Volts B) 5 VoltsC) 12 VoltsAll are DC voltage. (The incoming electricity from your home or business, is AC voltage){In comparison two D cell flashlight batteries produce 3 Volts DC}Use a multimeter to test the voltages. If you do not have access to one, an economical multimeter can be purchased for around $8 to $12. A multitude of stores carry them. An auto parts store is but one example.Analog or digital, it doesn't matter. (I prefer Analog)Set the Function Knob to DC voltage. (If just a symbol is used it is a dotted line over a solid line)If there is more than one setting for DC Voltage, set it to the 0 to 50 Volts scale. (0-50)The red probe lead is the Positive lead.The black probe lead is the Negative lead.The Positive probe lead touches the power wireThe Negative probe lead touches a Ground wire.The 3.3 Volt power rail, the 5 Volt power rail, and the 12 Volt power rail, are the power wires.Test one at a time.ALL Black wires are GROUND wires.Test at the ATX main power cable's connector.The ATX main power cable is plugged into the motherboard. The Power Supply is plugged into power.The ATX main power cable used for a Gigabyte GA-K8VM800M motherboard,is a 20-pin ATX main power cable. This is an example of a 20-pin ATX main power cable,
http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20Note the photo to the far right. The ATX main power cable is plugged into the motherboard. Testing the voltages is done at the Back of the connector. Back of the ATX main power cable connector. The Back of the connector is where the wires go in.The probe leads tips, will not fit down into the socket holes, next to the wires already present.Suggest use an adapter. Suggested adapter is a paper clip.The paper clip is straightened out, then inserted down into the socket hole, RIGHT NEXT TO THE WIRE that is already there.The paper clip Must go down into the socket hole, to touch a metal terminal.At the end of every wire going into the ATX main power cable connector, is a metal terminal. You have to go down past the insulation of the wire, and touch the metal terminal with the paper clip.A) The Orange insulated wires are 3.3 VoltsB) The Red wires are 5 VoltsC) The Yellow wires are 12 Volts.Example to test a 3.3 Volt power rail;Power Supply unplugged from power insert a straightened out paper clip into a socket hole with an Orange wire. Leave it sticking up.Now insert a straightened out paper clip, into ANY socket hole with a Black wire. (Ground)Plug the Power Supply into power. Touch the red Positive probe lead of the multimeter, to the paper clip for the Orange wire. Hold it there.Now touch the black Negative probe lead to the paper clip for the Ground wire.(Black wire)You should read VERY close to 3.3 Volts.Same procedure for the 5 Volt power rail, and the 12 Volt power rail.{Power Rail;All 3.3 Volt (Orange wires), end at one central point in the Power Supply.This central point is the 3.3 Volt power rail.Same for the 5 Volt, and 12 Volt wires.You can test any wire of that voltage, and be testing the entire power rail, for that voltage }Power Supply checks out?Graphics chipset.Chp and Chipset are slang terms for I.C.Integrated Circuit,
http://en.wikipedia.org/wiki/Integrated_CircuitThe graphics chipset is a GPU.Graphics Processing Unit,
http://en.wikipedia.org/wiki/GPUA GPU can be soldered directly to the motherboard, or to a removable card.Soldered directly to the motherboard is Integrated Graphics.Also known as OnBoard graphics. (ON the motherBOARD)Soldered to a removable card is a Graphics Card.(Full name is Graphics Adapter Card)If you are using Integrated Graphics, try using a graphics card.If the graphics card works, the problem is bad Integrated Graphics on the motherboard.The graphics card bypasses using Integrated Graphics.{The above is that you are seeing No Signal on the monitor.If not check the monitor, AND the monitor cable to see if they are good. Test on a known to be good, working computer }For additional questions please post in a Comment.Regards,joecoolvette
