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why does my computer turn on but not boot up

so. ive been having the same problem as everybody else (for the most part)
i feel ive taken all the necessary steps but I want to be 110% sure that ive come to the correct conclusion. Mainly because the computer is not actually mine. I'm just more technical than the owner and have a decent common knowledge about computers and electronics so here's what happens. DVD drive lights up, opens and closes Manual shut down is not possible. ive held down the power button for 2 minutes straight and no shutdown occurs PC does not boot. this is what ive done so far. i've disconnected the RAM and turned on the computer. no beep. no nothing ive attempted to clean the RAM with an eraser. no luck i've attempted switching ports that the RAM is plugged into. no luck i've removed the ethernet card and restarted the PC. no luck I've removed and reinserted the BIOS battery located on the MoBo. no luck I've cleaned out all the dust from the fans and boards and once again. no luck i can't seem to remove the CPU heat sinc from the CPU to do the heat test. BUT. ive left the PC running (everything connected) and I can feel the heat sinc heating up after about a few minutes. which leads me to believe that the CPU is fully functional. so most people would say, open and shut case, Johnson. What the heck is your question? well, its the CPU fan the PC has been running for a few minutes now, the CPU is obviously heating up and the cooling fan hasn't kicked on yet. so I attempt to spin the cooling fan manually (with just my fingers) and the fan continues spinning but at very low RPMs. probably not even quick enough to cool a snowball in the north pole. so my question is. (finally) is the CPU cooling fan being effected by the incapabilities of the MoBo? once again. i'd like to be 110% sure of what the exact problem is here, mainly because the computer doesnt belong to me. and to tell a friend he has to replace his MoBo and then find out afterwards that wasn't even the problem is nothing short of. messed up to have him replace his MoBo. solve his problems for a week or two and then have his CPU blow up on him after reading all 7 pages of this thread ive come to the conclusion that this is a pretty common problem with Acer PCs.

I know what brand of computer NEVER to buy thank you, and goodnight I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems. If not, continue. I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST. Breadboard - that will help isolate any kind of case problem you might have. Breadboard with just motherboard, CPU HSF, case speaker, and PSU. Make sure you plug the CPU power cable in. The system will not boot without it. I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced. Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting. At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3. 3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot. You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires. A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires.

That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch. This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots. Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST. At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface. Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.

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