Well things like this can happen after turning on a machine which wasn't used for several days.
- Do you see that your Hard Drive indicator flashing? If so it may be working without a problem.
- Do you see your Processing Indicator flashing? If not, that means the processor is not working due to an internal problem.
- If CPU fan doesn't run either Fan it not getting enough power or it is having a failure.
- Have you checked your Power Unit? There is a fan inside the PU as well. If it doesn't work, PU will not be turning on. This might be a problem with PU itself or PU fan. If you know how to use multi meters, you can check whether PU supplies power successfully. Yellow (12V DC) and Red wires (5V DC) carry DC Voltage to Hard drive. For SATA its bit different. Black wires represent Ground. So you can check if you have a multi meter.
- You can check 20 or 24 pin Molex connector as well.
- Here is a link to pin diagrams and their Voltages.
- Check the Fan Connector as well.
- Have you checked your Video Adapter's connector? If the Adapter has a loose connection then the Signals might not be Carried to the Monitor.
If the Fans work:
- Finally you have to check your RAM and Processor.
- Remove RAM cards and keep them without reconnecting for a while. Like 10 minutes. After that connect them and check.
- Remove your CPU fan with heat sink and turn the machine on for 10 seconds(If the fan works. If it doesn't work no need to follow this step since without the Processor fan CPU will not be turned on). The shut it down immediately. Check whether the Processor gets heated. If not either it is not functioning or its not getting power.
- Remove your Video Adapter as well. Connect it properly. Clean its connector pins.
- If the Hard Drive turns on and work that means its a problem with your Video Adapter. May work after cleaning the Connectors.
- If nothing works, please remove your CMOS battery with other Peripherals and keep for 10 minutes and reconnect every piece and then boot the machine. Make sure you adjust the BIOS settings again such as System Time.
- If the power unit works but no HDD functionality or No Processor run at all, then it has to be a problem Related to *********** Board. Especially power carrying Buses are facing Difficulties. If processor doesn't get heated up that means either the Mother Board or Processor Have been failed during he booting process.
- If Processor temperature goes up but no response of the Hard Drive means: Either RAM or Video Adapter Failed. There is no reason for a HDD failure. If reconnecting the Video Adapter (assuming other devices working well) doesn't give output (if you have a separate device however) use the Built-in module. If you are using the Built-in Video Adapter, unfortunately you will run out of the second option. You can check using an external device if you have a vacant port.
- Remove your RAM and check whether your machine gives a beep sound out. If it doesn't that means there is something wrong with Mother Board or CMOS chip.If you have 2 or more RAM cards, connector one at a time and check by booting the Machine.
- If the Fan doesn't work change the socket of the (connect to a different location such as chassis fan connector and check whether it works. If it works that time the CPU Fan connector has a failure. If the Fan doesn't work at all (if you are sure that PU is functioning properly as well) replace it.
Run the checklist and try to locate the faulting module. If you have lack of experience however its good to take the machine to a tech.
Feel free to contact again if the problem persists.
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