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Computer turns on - Black screen (always)

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by techasaurus

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Hey all, I just now found this forum thanks to a good friend of mine who just retired from 10 years at Microsoft. So far I LOVE the site!

Anyways, I've been repairing computers for 7 years now as my full time job.

I had a customer call me recently and I picked up her desktop and brought it back to my home office.

When you turn the computer on the hard drive boots up, the fans spin, and all the lights work. The PSU light on the back goes green, and it acts as if it's booting up.

Only problem is the monitor (plugged in and turned on) does not show anything on the screen. When I tap a button on the monitor I get "In Power Save Mode - Press key on keyboard or move mouse" - Nothing.

I put in a video card and tried that method, same issue. I reset the memory, checked all of the computer plugs, and well, I'm at a lose for words. I cannot enter the bios, enter safe mode, anything. I'm stuck with a black monitor screen.

Could this be a power supply issue or a mobo issue? If so, how can I troubleshoot further without swapping those out (time consuming)?

This machine is a HP Pavalion a1737c and runs Windows Vista.

It is using the onboard mobo video connector (until I tried a vc I put in).

Hmm... Any clues? Thanks all!

46 replies

by boxfiddler

that the monitor itself is faulty? Or the monitor connection cord/connector? Or if there is a 'transformer' (probably not the right word) that sits between where the monitor plugs into the wall and where that cord plugs into the monitor is bad? Or could the connectors at the monitor itself be bad?

IOW, does the monitor work when attached to a different computer? Or, does another monitor work when attached to that computer?

by techasaurus

Box, yes, the monitor works. Actually I've tried 3 different monitors, and I know they ALL work. The customers monitor worked as well on their other computer (that they tested prior to calling me).

So it is not a monitor issue.

by oh smeg

But that doesn't mean that it needs to be fitted to the Case just that you need to unplug the existing power supply should be 2 Plugs to the M'Board and 1 plug to each drive inside the computer.

Lay the case on it's side place a Known Good Power Supply somewhere that is useful and plug in the 4 or so connectors required.

Then plug in the Known Good PS and try to turn on to see what happens.

If nothing still happens the M'Board is dead.

Col

by boxfiddler

if the mobo is dead why does everything but the monitor power on?

To quote the OP:
"When you turn the computer on the hard drive boots up, the fans spin, and all the lights work."

edit the usual

by techasaurus

Yes that's a good question. I can hear the hd and everything else boot up, this is a power supply thing, so it would be the mobo which would send a signal across the board to/from the onboard vid card and then the pci vid card.

I'll swap the PSU out tomorrow as a start.

Hmm, I don't have a mobo like this on hand, will have to go find me one.

Turns out customers computer is 25 days out of warranty from HP/Compaq, go figure, haha.

by oh smeg

Isn't producing the 3 V DC Rail and only the 12 V DC Rail.

That would allow the HDD's to power up and fans but not the CPU.

How is that for starters? :p

Or The Power Supply could have been overtaxed and no longer producing the necessary Ampage while still producing the correct Voltages.

Something very common with HP Dedicated PS's those one as they are underpowered from the very start and run harder than they need to.

Besides this is only a starting point and it's far easier to change a PS than a M'Board. Also if the PS is damaged you don't want to trash a new M'Board by swapping it out without first checking that the PS isn't damaged do you? Seems a tad expensive to test the other way to me at least but them I pay for my mistakes.

Col

by rob miners

I thought that I had the Voltage correct.

What happens when you start the computer?
When you turn on a PC, the power supply starts up and waits until any startup spike or sag has passed and the power output has stabilized. Then, it sends +5V through pin 8 (on an ATX connector) or pin 1 on the P8 connector (on an AT-style power supply). This is called the Power_Good signal. The motherboard looks for this signal, and if it finds that between +3.0V and +6.0V is passing through the Power_Good pin, it knows it?s okay to turn on and start making use of the rest of the power coming through the other pins on the power-supply-to-motherboard connector.

If the motherboard is receiving power from the other pins but the right voltage is not coming through the Power_Good pin, it waits, continually resetting itself until it receives the correct voltage on Power_Good. This system helps prevent electrical damage to sensitive components from a malfunctioning power supply. The original designers of the PC thought this was a very conservative system that would ensure freedom from power supply problems, but I will explain later in this article, problems can occur anyway.

The power supplies in PCs are of the switching type (as opposed to linear). Because of this, they do not run without a load?that is, without some device drawing power from them. If you turn on a power supply that is not connected to anything, it either won?t work at all (best case) if it has protection circuitry built in, or it will fry itself within a few seconds (worst case) if it does not. Therefore, when testing power supplies, you should always have something connected to them, even if it?s an old broken-down motherboard and an obsolete drive. How much do you need to connect? It depends on the age of the power supply. On modern systems, most motherboards draw the needed amount of current by themselves; but on older systems, or with larger power supplies, at least one disk may need to be connected as well.

Symptoms of a faulty power supply
A failing power supply can cause all sorts of problems that do not appear to be directly related, leading the less experienced technician on a wild goose chase through memory, processor, motherboard, and hard disk errors. Often, the problem seems to jump around, such as a memory problem that reports a different memory address as faulty each time or spontaneous rebooting after a random amount of time. There are three reasons a power supply can cause a problem:

Physical failure?In a failing power supply, the power supply is not generating its rated amount of power or it is providing the wrong voltages on some wires. The PC generally will not start at all if such a condition exists. (See the next section for help determining whether a power supply is working correctly.) Replacing a faulty power supply is the best solution as repairing power supplies can be dangerous for inexperienced technicians and is seldom cost effective.
Overloading?On an overloaded power supply, there is not enough wattage to support all the devices plugged into it. On a system with an overloaded power supply, problems will often occur at startup, when all the drives are spinning up, or when accessing a drive. (See the preceding section to calculate how much wattage you need in the system. Then replace the power supply with a higher-wattage model if needed.)
Overheating?This happens when the power supply fan (or processor cooling fan) is not doing its job adequately or when the system case?s airflow is obstructed. Most computer cases are designed to pull fresh air through the case across the major heat-producing components. The air flowing through the restricted space is very important. If you remove the case cover or leave empty-slot covers off, the air does not flow as designed and overheating can result. If the system starts up okay but then starts having problems after several minutes of operation, inadequate cooling is almost always the problem. Make sure the airflow path is unobstructed, that the processor heat sink or cooling fan is in place and operational, and that the power supply fan is working quietly and correctly.

http://articles.techrepublic.com.com/5100-6349-1046822.html

forgot link again

by techasaurus

Hey True Blue, read all that and tried all of the tips/tricks they recommend. Still, nothing. Hmm.

by sleepin'dawg

If graphics are integrated on the mobo you'd have to switch them off before using a card. This is either a dip switch or jumper change.
I'm assuming the card you inserted works on another machine. BTW what video card did you try?
The other thing to try is cleaning the card connector fingers and the connector slot with iso-propyl alcohol as well as using canned air to blow any debris out of the slot.
Make sure the card is firmly seated in the slot but take care that you don't flex the mobo because you might crack a trace and that would be next to impossible to find and remedy. In the event that the mobo was flexed there is the outside possibility that a cold joint was created; you could try slightly jiggling the card and connector but that's a very faint hope and is not to be considered a long term fix.

[b]Dawg[/b] ]:)

by techasaurus

Hey sleepin, I tried first to use the intergrated plug on the mobo, nothing. Then installed a seperate card. Not sure what it is it's so old. I actually have 2 of the same cards and they both work in my "wtf machine" where I test various things for known issues.

Hmm.

by techasaurus

True,

I'll go find me a PSU and also a mobo and try the PSU first then the mobo. Thank God for returns/refunds :-)

by oh smeg

The ideal hardware works for the time that the Warranty is available and then fails so that the customer has a choice of paying for the repair which earns HP more money or buy a New One.

Part of the reason why I no longer sell HP products as their Warranty leaves a lot to be desired. Here with a lot of their stuff they don't repair they swap out. Good idea while UG but a terrible idea when the customer is the one paying for the [b]Repair.[/b] :D

What you need to know about PS's is that they produce several different voltages and any one can fail to work. So if you can hear the HDD's spin up and see the Fans work this is telling you that the 12 Volt rail is working but tells you absolutely nothing about the 3 Volt Rail or the 5 Volt Rail both of which may not be working.

The 3 Volt Rail powers the CPU and the 5 V Rail provides power for the Drive Controllers.

Also what would happen if the PS was no longer producing 450 W but only providing 100 W to the computer? Electronic Parts can fail in such a way that they loose the ability to work as designed while still appearing to function.

Col

by oh smeg

If you don't have the Pin Out of the ATX Connector I'll post back with one. But Antec should have this in their Web Site.

But you still need to confirm that the Ampage is correct. This is something that Power Supply Testers don't actually cover. It keeps you on your toes. :D

I used to work on HP units that they couldn't repair years ago and I routinely found Faulty PS's that where incapable of powering the unit. This was more common if parts had been added though. I remember one Evo that worked for 6 months with a Optical Drive & Video Card added and no matter what HP changed it didn't start working again. When it was sent to me I plugged in a 450 W Antec PS and the thing sprang to life. Not sure what HP here did to fix it though as they had already changed 5 PS's and the M'Board a couple of time. I presume that they either continued to change PS till they found one that worked or they removed the extras and told their customer they these where no actually supported though without a Optical Drive I'm not sure how the Customer was supposed to reload the thing when that became necessary.

Col

by boxfiddler

I read your earlier explanation to Shawn about 3 and 5 volt rails. This is something that I did not fully understand before. Thank you for the clarification.

I stopped buying 'off the shelf' after the 1st one, and I never scrimp on components. But I will certainly copy and paste your information to my collection.

'Davette'

by techasaurus

Yes, thank you, I learned a lot myself and already printed the info out and have it posted on my wall, haha.

by techasaurus

Go figure, thanks HP.

No wonder I own an Alienware as my personal prior to Dell buying them.

5 years old and not one problem ever!

by rob miners

Not a bad article, and did you notice who wrote it. :)

by rob miners

No I was just pointing out the fact that it was a "female", Faithe Wempen who wrote that article. Chalk one up for the girls. :)

I was stumped when I found out that the Sgt was female. In all her correspondence and there were a hell of a lot of posts there was no hint. One clever Lady. :)

No I am the only boy, the second eldest with five sisters. :)

by boxfiddler

I made a point to try to avoid giving away my sex. The odds are that I am somewhat noticeably female if one is attuned to the gender differences that could have given me away. But it wasn't until TiggerTwo let the cat out of the bag that I stopped being deliberately 'asexual'.

I am enjoying the podcasts in no small part because I am discovering whether or not my assumptions about the sex of the participants is correct.

by rob miners

and she disappeard, Unfortunately. I like it when women stand up for themselves, my wife does and I'm proud of her. :)

What I am really trying to say is don't be embarrassed to show your gender. :)

by boxfiddler

more like a bizarre game to play with myself that can really only be played under these more or less anonymous circumstances. An exercise in writing in an odd sort of way.

by older mycroft

Regarding the art of knitting: "Knitting huh? - I didn't take you for that kinda guy!"

Yes, oh yes - she ROARED at me! I crawled off into a corner and hid.

by rob miners

and she was off like a bolt of thunder :)

I bet she likes cats too. :)

by techasaurus

Hey all, I tried a new power supply, and nothing... No mother board beeps. I unplugged every single cable from the mobo except for the power on and power off pins, and no beeps.

So it's either the processor or mobo, or both. That sucks for the customer.

by techasaurus

Reseated the ram and put in 2 new sticks fresh from the store (didn't have any on hand).

So unless 2 new sticks from the store are bad, I dunno what else, lol.

Reset the bios with the onboard cmos jumpers, nothing.

by rob miners

but have you reseated the CPU and reapplied CPU Grease. Apart from that I can't think of anything else to try. Unless you have a spare CPU. :)

by oh smeg

To see if you get any signs of life from the M'Board.

Try removing everything except the GPU & Heatsink and Power Supply leads to the M'Board and see if there is any difference. Of course leave the System Speaker connected to see if the M'Board tells you that things are missing.

Also what was the stated problem when you picked it up?

That might be of some assistance here.

Col

by Former member

Shorting, you will have to look underneath the motherboard and see if there are any small red disks (seperaters), that keep the motherboard away from the metal posts. Replace if there is not any. Hope this helps you.

Please post back if you have more problems or questions.

by arujammer

I'm also having this problem with Vista.

But i have manage to get something on the screen, but still no OS, since i formatted the Harddisk and refresh de BIOS.

But here what worked for me till now:

Disconnect all drives,exept the OS HDD and restart the PC.
If you still get the black screen, use the other end of the flatted cable.

by techasaurus

Yes, tried this as well.

Still nothing happens.

Could this be the processor perhaps?

by rob miners

Step 4: Resetting and updating the BIOS
In case an item was changed in the BIOS, such as the primary display device setting, use the following steps to reset the BIOS back to its default configuration:
Turn on the computer and press the keyboard key that enters the BIOS Setup screen key when the keyboard light comes on. The key to enter the BIOS should be one of the following:
HP and Compaq desktop computers that came with Windows Vista, press F10 .
For HP Pavilions desktop computers that came with Windows XP or previous versions of Windows, press F1 .
Compaq Presario desktop computers built after 2002, press F1 .
Compaq Presario desktop computers built prior to 2002, press F10 .
Wait 5 seconds.
Press the F5 key to restore the default settings of the BIOS.
Press Enter to accept the change and wait five seconds.
Press the F10 and then the Enter key to save the changes and exit from the BIOS.
The monitor should now display the first screens received from the computer (the logo screens). If not, find and download the latest BIOS update if one is available for your computer.
If a BIOS update was not available or the monitor is still blank, continue to the next step.

http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph04760&lc=en&cc=us&dlc=&product=3355630&rule=39940&lang=

by techasaurus

True Blue, thank you for the link and for digging into this.

I found this useful a few nights ago, I tried everything but nothing happened :-(.

by Former member

Open the computer case and switch on the computer now (and very slowly) press down on the processor, you might need to reboot while you do this, do you see any text?. Why i say this is that i had similar problem today and i did the above and found it was the processor not connecting properly.
Hope this helps you.

Please post back if you have more problems or questions.

by kawasaki_ninja_ec22

man, im having the same or similar problems. no signals to the monitor. monitor and cables are fine(im positive and i've tried it). i new parts and built a new computer but this happends.
I tried using another graphics card and RAM. and still the same problem. there were no beeps when i turned it on. and the disk drive doesnt open when i turn it on, but i opens when i unplug the data cable.

NEED HELP!!plz

Ps. shawn, u got more responses than i did i only got 3 LOL

by kawasaki_ninja_ec22

there are no beeps which means that the RAM, graphics and cpu is situated properly. so either the M/B is broken or my NEWLY bought 500W PSU is broken.
plz respond :D

by oh smeg

So start with checking all connections especially the Front Panel Connections.

If every thing is correctly connected change the Power Supply. If nothing still works change the M'Board

Nothing else to do in a case like this other than say that the M'Board should never have got mounted in the case without first testing. It saves a lot of time & effort knowing that you have working components before you start assembling. You should test them before placing the M'Board in a case.

Col

by kawasaki_ninja_ec22

i've checked all the connectors and read the manual 10 times over, lol.
the thing is that i dont have another computer to test the parts on. and if i were to go and claim that the M/B is faulty and if its not, id have to pay a service fee of $44 which is a total ripoff.
If it was the m/B that was faulty what'd you reckon is the problem with it.

by techasaurus

It was a mother board issue. Swapped the old mobo out for the new one and she powered up just fine. Ran through her cycles, screen appeared, etc...

Now I just have to log into Vista which is locked down with a user/pass, haha.

Sooo dead mother board. Neither of them beeped, so let that be a warning to us - not all mobo's beep.

Thanks all, we made this a great thread :)

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