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Blank screen on bootup


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#1
gtipler

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Hello to whoever is able to help,

Recently my computer seems to have dug itself 6 feet under. I went away for a week, the system was working fine before I left but as soon as I came back and went to switch it on, it wouldn't. The desktop itself seems to boot up fine, all the fans start etc (ive opened it up to make sure all fans are functioning). However the screen stays blank saying that there is not input signal being received.

Ive checked the video cable and it looks in fine condition (not broken/bent pins). Im not great with computers but I just cant work out why it suddenly stopped working from one day to the next when it was out of use. When it used to work it would emit a signal beep on start up, this beep no longer occurs. I dont know if this is because it isn't booting up properly or not due to not being able to see the progress because the screen is blank.

Any suggestions will be greatly appreciated and if you need and questions about the system I'll try my best to answer them as well as I can.

Thanks in advance
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#2
rshaffer61

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Hello gtipier.... Welcome to
GeeksToGo, :D
;) ;)

I'm sorry to hear about your issue. We will try to help you resolve this as soon
as possible.
  • Please understand we are all volunteers and we are not here all the time.
  • Sometimes it may be a extended amount of time to get back to you. If it has been
    more then 3 days please shoot me a PM and I will try to get back to you quickly
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  • Please do the following and supply the requested information as needed. If you
    don't understand my instructions please ask and I will try to explain them
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  • Do not attempt any steps unless instructed or ask before to
    make sure they will not cause any further issues.


Firsts step is to determine if it is the system or the monitor.
Easiest way to do this is to try a known working monitor on your system or try your monitor on a known working system.
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#3
Digerati

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Well, normally I was say to try another monitor first to isolate the problem to the monitor, or the computer. But a single beep typically means it successfully passed the POST - power on self test - and now that you no longer hear that, it points to the computer and not the monitor.

The fans spinning means your power supply is delivering +12VDC, but the PSU must also supply +5V and +3.3V and if me, that is where I would start looking.

Here is my canned text on testing PSUs:

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronic repair facilities.

Fortunately, there are other options that are almost as good. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

Note the required voltage tolerance ranges:

Posted Image
NOTE: Disregard the -5VDC reading. It is no longer used.


Swapping in a known good supply is a tried and true method of troubleshooting used for years, even by pros. If you have access to a suitably sized, spare power supply, carefully remove the suspect supply and replace it with the known good one, and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply.


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#4
gtipler

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Thanks for the quick response.

I just plugged my own monitor into a working desktop (with my own video cable to try and rule that out as an option as well) and it worked fine. So the issue must be with the system itself
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#5
rshaffer61

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I have to agree with my esteem colleague on this now. It sounds like more the system is not booting.
I would start with the PSU as suggested. :D
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#6
gtipler

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Ok thank you. I don't think I will test the PSU myself as I have no idea what I am doing, but when I get the results back from having it externally tested I will update this thread. Thanks again for the input
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#7
rshaffer61

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No problem and good luck. If the PSU tests ok then we will continue with diagnosing and hopefully resolving the issue with you. :D
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#8
gtipler

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Quick question. This may be a dumb question, but you say previously that the 12V output from the PSU would be working as the fans are starting up. So I'm taking it the 5V and 3.3V output run the other components such as graphics card, sound card, CPU, etc. Would this be correct? If so, is it important to state than when switching the desktop on, the fans on the graphics card are also starting. Does this suggest the power running to them substantial?
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#9
rshaffer61

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It may have enough to start but does not indicate if the voltages are steady or within tolerable ranges.
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#10
gtipler

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ah ok. Thank you
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