Monitor only activates after 5-10 pwr cycles.

May 16, 2011 at 01:29:25
Specs: Windows XP
A few weeks ago, i rebooted my computer and the monitor failed to turn on with the reboot. I manually turned the pc off and back on again, and the monitor powered up normally. Since then it has progressively gotten worse... every time i reboot/power off the pc, i have to turn the pc off and back on 5-10 times before the monitor will come on. After troubleshooting, I feel like this is more of a PC problem than a video card/monitor problem... but not sure what it is.

Here is more detail of whats going on:


The problem: Power off the computer... both the PC and monitor turn off, and the monitor light turns from green to amber. Press power on the PC - the keyboard lights immediately (and briefly) flash green and the PC fans/drives start running, but the monitor stays off with an amber light. Eventually, after 5-10 power cycles, the monitor will turn on and give a green light... when this happens, the keyboard lights flash green a 2nd time at the same time the monitor turns on.


I have tried using another monitor, and the same problem happens.

I am using the integrated graphics vga port... i tried installing a video card, and the same problem happened.

I disconnected all CD/HD drives, and the same problem happens.

I removed all ram -- leaving only the monitor and keyboard/mouse connected. I powered up the PC to see what happens... only every 5-10 power cycles would i receive the BIOS beep indicating (im guessing) a ram problem (1 short, 1 long repeating). Every other time, the motherboard fans would just power up and run without any beeping.


Even though the hard drive powers up, it doesn't appear to do anything past the initial power up when the monitor fails to activate. Only when the monitor turns on do i hear the hard drive load the OS. Each time i power the system up, and the monitor doesn't come on, i do not hear any hard drive activity during the time it would normally be loading the OS.

I'm not sure if this is related, but i also recently developed an intermittent problem where my screen suddenly displays nothing but unchanging digital garbage... when this happens, my entire pc locks up and i am unable to do anything except manually power off the system.


Seeing that when i remove all the ram, i only get the system error beeps at the same frequency that the monitor activates when everything is connected, it tells me that it probably isnt the ram, monitor, or hard drives. So what does that leave? PSU and motherboard? Any ideas?

hp a1600n 2ghz 1gb ram
windows xp sp3
asus-a8m2n-la motherboard

Thanks for any help!

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May 16, 2011 at 02:41:05
I would start looking at the PSU.

One of the lines from the PSU is called "power-good". When the PSU is switched on this line is first held at 0V. The BIOS monitors this line and while it is at 0V is does nothing except sends a continuous reset signal to the CPU which effectively prevents the CPU from doing anything. The is to prevent damage if the COP or motherboard is presented with incorrect voltages which is possible with the initial current surge,

Once the PSU is up and running and all the voltages have stabilised this line is raised to 5v and the boot up continues. This usually takes less than a second. A faulty PSU, such as a flaky voltage regulator or a failing capacitor can keep this line at 0V. Occasionally everything works right but mostly it doesn't.

You can monitor this line with a digital voltmeter. It is the only grey cable in the power supply.


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May 16, 2011 at 07:38:35
Thanks a lot, i will start looking into this. I'm hoping it's just a PSU issue.

Also, to add a little more detail:

After i press the power button, the fans activate and there is about a 2-3 second delay before the HD/CD drives power up... this may be the safety delay you were talking about. Even if the monitor doesn't engage, the HD/CD drives power up (after the 2-3 sec delay) EVERY time i press the power button. When the monitor eventually powers up, it powers up at the same time that everything else does... right after the 2-3 sec delay.

And again... even though the HD powers up every time, i only hear HD activity when the monitor has also activated.

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May 16, 2011 at 09:13:37
The hard disk will power up when switched on as it gets its power directly from the PSU. It wont do anything until when it gets the reset signal from the north bridge and it wont get that until the power good signal is raised. During the POST sequence the video get initialised before the hard disk, CD or floppy if one is available.

If the CPU and memory gets incorrect voltages it will get confused between ones and zeros and throw a tantrum. In the half second it takes for the power to stabilise normally the CPU could execute millions of instruction and if the voltages are wrong, interpret them incorrectly and lock up the computer before it even gets started.

That hard disk can tolerate a little over voltage or even under voltage but the CPU and memory can't.


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Related Solutions

May 17, 2011 at 11:35:08
Ugh... well it finally quit working all together. I was doing some troubleshooting, and once when i turned it on, the fans all started running at a higher speed (or i guess it's a higher speed... they are really noisy now), and the monitor will no longer activate. I tried using a different PSU, and got the same result... noisy fans and no monitor. One time in the course of swapping things, the fans dropped to their normal (quiet) operating speed, and the monitor instantly powered up... that happened twice... but besides those two times, it is just noisy fans and no monitor now.

Guess ill have to try a new motherboard, unless anyone has some ideas. oh and i monitored the temperature for a while before stuff stopped working, and it seemed to be normal. i also reseated the cmos battery and reseated all of the fan/usb/power cables.


EDIT: after i submitted this, i tried starting it a few more times... i turned it on and off really fast (because i was just mashing the button) and that must have caused something to reset, because the fans dropped to normal speed and the monitor came on. i turned it off, and restarted... the fans are at normal speed now, but it seems the monitor isn't going to come back on (have power cycled it about 20 times). so who knows... i guess ill just buy a new motherboard or pick up a used pc somewhere.

thanks again

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May 25, 2011 at 19:06:57
turns out it was the motherboard. ordered a new one (well... an open box from newegg, heh) and used the same memory, psu, and everything else, and it fired right up. sucks that the other one pooped out, but i got a nice deal on a video card... going from the geforce 6100 onboard video to a gt 240 card... it's like going from a tricycle to a corvette, lol.

i read an article on bad capacitors ( and the symptoms it listed were almost exactly what i was experiencing... that could have been what the actual problem with the mobo was.

anyway, thanks for your help.

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