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Help! Monitor is blank after starting the computer

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July 28, 2010 12:54:50 AM

Help! Monitor is blank after starting the computer

I have a HP Pavillion Elite m9517c

I upgraded to windows 7 on a new HDD and for about one week, everything worked perfectly. Now all of the sudden the monitor is blank after starting the computer. The monitor works with another computer and so does the monitor cable. I tried the following:

1) removing and reinserted the RAM

2) removed and replaced the HDD

3) tried a new video card

4) tried to plug in a VGA and DVI into the onboard sockets (after removing the 9300 graphics card.

4) went through most of the steps from the HP help guide on this topic (see link below)

5) tried to reset the CMOS (with and without removing battery)



Nothing!



The computer looks like it is booting up, keyboard lights up, but nothing on the monitor - no BIOS splash screen.



http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph......
a b C Monitor
July 28, 2010 6:57:28 PM

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
yes? I mean work through, not just read over it.

Breadboard - that will isolate any kind of case problem.
http://www.tomshardware.com/forum/262730-31-breadboardi...

The breadboarding thread has a paragraph about how to build and test a PC in stages.

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. If your case or motherboard didn't come with a system speaker, you can buy one here:
http://www.cwc-group.com/casp.html

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.

At this point, you can sort of check the PSU. Try to borrow a known good PSU. 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.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

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 or long single beeps indicate a problem with the memory.

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.

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.
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July 29, 2010 5:55:53 PM

JSC - Thank you for this helpful post!!

This is going to be my weekend project.

I had one question: is it common that a PSU "dies" but still looks like it is working?
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a b C Monitor
July 31, 2010 6:33:37 PM

It is not uncommon.
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July 31, 2010 6:43:17 PM

Okay, now I have a really silly question for you. I'm a bit nervous about taking out the motherboard (never done this before). Do you think I could put another computer with a good power supply next to the one that is not working properly and just plug in the main power cable. Then turn both computers on. The power supply is working on the defective computer - it's just maybe not putting out enough power so additional power from the other power supply might tell me if the power supply is the problem.
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