Pertaining to a Compaq Presario SR1500NX Desktop PC;
http://h10025.www1.hp.com/ewfrf/wc/product?product=472140&lc=en&cc=us&dlc=en&lang=en&cc=usLet's see if the problem is a $5 ATX Power On switch, or the Power Supply.Use a jumper wire on the 20-pin ATX main power cable.Bypass the Power On switch.IF, the Power Supply comes on you have a bad Power On switch.IF, the Power Supply does Not come on you have a bad Power Supply.This is a look at your motherboard with no hardware components installed, and no cables,
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00069442&tmp_task=prodinfoCategory&cc=us&dlc=en&lang=en&lc=en&product=472140Scroll the page down to the illustration, and photo of the motherboard.Looking at the illustration look at the Right/Middle. The ATX Power Connector, is the female connector on the motherboard, that the 20-pin ATX main power cable plugs into.Match that up to the photo. Whitish long connector, with two columns of 10 socket holes.This is a general example of a 20-pin ATX main power cable, and it's respective connector on the motherboard,
http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20[NOTE* Color of the connectors NEVER matters ]The photo to the right shows the 20-pin ATX main power cable, plugged into the motherboard. This is how it should be for the test. Also the Power Supply should be plugged into power.Look at the Green wire, going into the Back of the power cable's connector.This is the Soft Power On wire. Abbreviated as PS_ON.This wire is briefly jumped to A-N-Y Black wire. ALL Black wires are Ground wires.The preferred jumper wire is a paper clip. The paper clip is straightened out, then bent into a U-shape.The middle of the U is wrapped a few times, with black plastic electrical tape.This area is for your fingers, and thumb to hold onto.Turn the U upside down. The 'legs' of the U-shaped jumper wire, is what is used.Look at the squarish socket hole for the Green wire, in the Back of the power cable's connector.There is room for the 'leg' of the U-shaped jumper wire, to slide down in.Slides RIGHT NEXT TO the Green wire.Slides past the insulation of the green wire, and goes down in far enough, to touch a metal terminal.Every wire going down into the connector, of the 20-pin ATX main power cable's connector, ends in a metal terminal.Looks like this, (Except the left side is crimped over, on the insulation of the wire),
http://www.molex.com/molex/products/datasheet.jsp?part=active/0002081202_CRIMP_TERMINALS.xml&channel=Products&Lang=en-USThe right side is what you barely see, in the middle photo on the Playtool link. The, what look to be almost black spots, (24 of 'em), are the ends of the metal terminals. (Right side)For this reason you need to ensure the 'leg' of the jumper wire, is going down past the Green wire's insulation, and actually touching the metal terminal. Otherwise you have made no contact with the jumper wire, at all.The other 'leg' of the U-shaped jumper wire, goes down into A-N-Y socket hole in the Back of the power cable's connector, that has a Black wire in it.The contact made is no more than 2 seconds. (The Power On switch is a Momentary Contact Switch)Worried about Shock?1) There may be a small spark. This is just the way electricity acts when you complete a circuit, and touching an open wire.2) The Soft Power On circuit is 5 VOLTS DC.In comparison two D cell flashlight batteries store 3 VOLTS DC.For me? Shock is none, or minimal. YOU, may wish to wear a glove, on the hand that holds the U-shaped jumper wire.Just want you to feel safe.[Your Power Supply is an Inverter. It converts AC electricity from your home, or business, into low DC electricity.120 or 220 Volts AC down to three low DC voltages;A) 3.3 VoltsB) 5 VoltsC) 12 VoltsAll are DC voltage.{ Just like a line pole transformer steps down 7,200 Volts AC single phase, into 220 Volts single phase, for your home} ]BEFORE reaching into your unplugged from power, computer, FOLLOW Anti-Static Precautions;Anti-Static PrecautionsYour body carries Static electricity. Static WILL fry out (Short Circuit), the delicate hardware components inside a computer.Computer on a table, computer unplugged from power, computer case open; TOUCH an unpainted surface, of the metal frame of the open computer case.This action will relieve your body of Static.{You are 1/10th less concerned about getting shocked, as you are about Static shocking your computer hardware parts }IF you leave your computer in the middle of working on it, be SURE to Touch the metal frame again upon your return.Replace Power On switch:The Power On button is a plastic assembly. Inside the assembly is just a regular ATX power on switch. The following example is used in a LOT of Desktop PC's,
http://www.directron.com/atxswitch.htmlThe Front Panel of the computer is removed, to access the Power On button assembly.{ NOTE*BEFORE removing the Front Panel, make notes, and a drawing, as to where on the motherboard, ALL the wires go to from the Front Panel. This is in case you accidentally bump a wire loose }The plastic of the Power On button assembly becomes brittle with age, and heat from the computer.Once removed from the Front Panel, here are two methods I have used, to remove the Power On switch without breaking the plastic Power On button assembly;1) The Power On switch has been deemed to be no good. Doesn't matter what happens to it from here on out.I use a small bowl of VERY hot water, and dip the plastic Power On button assembly down into it, while holding onto the wires.Once it is felt the plastic has softened, I ease back on one tab, at a time, and ease the Power on switch out.You have to use finesse, and feel if the plastic is soft enough, before you start bending on any tabs.If not, re-dip in the very warm water, until you feel it is.2) Use a hair dryer, and heat the plastic up.In both cases you are dealing with a very warm to hot plastic object, so use gloves, and caution. [Want to buy the entire Power On button assembly? Sure. A) If you can find one. If so from an 'auction', remember the Power On switch inside, is U-S-E-D. Who knows how long it will last?Same if a local computer shop has one.B) HP Parts? May have one. If so, can you say OUCH? $$ ]Replace Power Supply:The Power Supply is just a regular ATX style, and 250 Watt.Approximate size is 6 inches Wide, 5-1/2 inches Long, and 3-1/2 inches Tall.This is one example of a Power Supply that is reliable, and compatible,
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1147669&Sku=U12-41529120mm fan is larger, than the 80mm fan of your old Power SupplyLarger fan turns slower, but produces more air flow.Turning slower also makes it quieter.(Unless you are gaming at full throttle! But the game sounds will overshadow the fan noise! Lol! )550 Watts. Means your computer won't strain for power.(Note* A computer ONLY uses the power it needs, and NO more.If it only needs 100 Watts, for example, when surfing the internet, it ONLY uses 100 Watts )Has all the power cables you'll need, and more. (Tie the extra power cables up out of the way with plastic ties. If you need them in the future, you'll have them)The ATX main power cable has a 20 + 4-pin connector.Means it can be used as a 20-pin ATX main power cable, which you need; or a 24-pin ATX main power cable.Want to test the Power Supply before buying a new one?Sure.You need a multimeter. An inexpensive, but good enough for this test, multimeter, can be purchased for as little as $8 to $12.Available in a multitude of stores. An auto parts store is but one example.Post back with multimeter in hand, and I'll guide you.Guide to opening the computer case, and removing Front Panel,
http://h10025.www1.hp.com/ewfrf/wc/manualCategory?cc=us&dlc=en&lang=en&lc=en&product=472140&Scroll down, click on the blue -> Upgrading and Servicing Guide(3.0MB)For additional questions please post in a Comment.Regards,joecoolvette
