Saturday, November 15, 2008

Yet Another Computer-Tech Bleg

I'm trying to do something nice, and it's not working out very well. Specifically, I need someone to help me figure out whether it's worth fixing the video output on an aging PC.

I built a new computer for our house awhile back (which was promptly struck by lightning, and is still getting replacement parts bit by bit) and was thus faced with What To Do with my old PC. I don't want the boys to have a computer we can't see, so there's not much point in giving the old one to them. But my sister expressed an interest in getting online and doing some digital photo work at home, and my old machine could handle that . . . sort of. Well enough to get her through until she knows what she wants in a new machine.

Here's the problem . . . . I scavenged a couple of PCI cards and a CD drive from the old machine for the new, then set it aside for quite awhile. A couple of days ago, I pulled it back out and hooked it up to the home network so I could switch all my old files to the new machine . . . . and the monitor was blank. No signal at all. Here's what I've tried:

  • Connected the monitor (a Dell LCD known to work) to the PCI video card output, then powered down and connected it to the motherboard output. Both failed; no signal.
  • Connected the Dell monitor to my new PC; good signal, video output shows up.
  • Connected another monitor (a Samsung LCD I use daily) to the old PC--no video output from the video card, the motherboard slot, or the motherboard slot with the video card removed.
  • On the advice of a friend who fixes computers, removed the little CR2032 battery for the BIOS and replaced it after a few minutes. That might have reset something, but it had no effect on the video output.
The thing is, this is a Compaq Presario 7478 (I think) and it's a weird model. The power supply is a smaller, proprietary size, and I believe the motherboard is the same way--so I can't just throw a new mobo into it. If there's a cheap, simple fix someone can share, I'd like to hear about it. But I don't want to put much more money into this thing, because I don't expect it to be more than a starter kit for her anyway. Help?

14 comments:

Joe Allen said...

Beyond removing the cmos battery, have you tried unplugging it from the wall for a few minutes - long enough for all caps on the board to discharge.

If the video were at fault, there should be an error beep - 1 long 2 short. It may not even be getting that far.

If you can't ever get it to fire up, you can get the stuff off of your hard drive with one of these: http://www.newegg.com/Product/Product.aspx?Item=N82E16812156102

Good luck,
Joe

Gudis said...

I would try removing the PCI board, attaching the monitor to the mobo video, and going into the BIOS to change the video boot option (if available).

Gudis said...

OK, published too soon. Then save the BIOS settings, power down, re-slot the PCI card, move the video cable, and power it back up.

Larry said...

If you're not getting any video at all on either video connection, it's not a good sign. You should at least see the POST where the boot sequence starts.

So 3 possibilities:

1. The PCI card AND on-board video are both fried.

2. Your on-board video component is fried but the BIOS is set to use it. If it were your PCI component that were dead, it should have been fixed in your BIOS reset procedure (when you removed the BIOS batery) because that would reset to factory defaults and use the on-board video.

This assumes of course that the battery you pulled was indeed the correct BIOS battery and not for a peripheral conmponent of some kind, that you waited long enough for the power to run out of all residual capacitors etc.

If this is the case there is not much you can do. For a desperate measure, look up the model and see if there are jumper settings that disable the on-board video and then hopefully the POST will pick up the PCI video card and start it in VGA mode (640x480) which will at least allow you to check BIOS settings and see enough to install drivers.

3. The motherboard or some other component is fried and it is just not POSTing.

Try taking the machine down to the absolute bare bones. One DIMM of RAM, take out the video card and any other PCI, ISA, etc devices.

If there is one hard drive make sure that the jumper settings are configured for "Master" or "CS-channel select", prefereably master. If there is a second hard drive, remove it. If the CD-rom is on the same cable/IDE port with the master hard drive, ensure that it is either set to slave or take it out completely.

Then try to boot it.

Mithras61 said...

You didn't say, and its important, so I'll ask...

Does it beep at all? If so, what beeps does it make (I'm looking for the pattern... normal Compaq post is two short beeps)?

If you aren't getting beeps, you are getting started (no video because no boot).

Also, if you can dig up the exact model number, I may be able to get jumper settings for that system. Some Compaq systems had to reverse connect the CMOS battery to clear the settings, not just remove power to it.

Also, does the system have a riser card that connects the expansion cards to the system board? If it does, it must be securely seated or no boot will happen.

Don Gwinn said...

There are zero beeps. I'm pretty sure I pulled the CMOS battery, too, because there's only one battery on the board. At this point, I'm just about ready to pull the hard drive for later stripping and take what's left to the range.

I talked to my sister last night and she's been thinking about a laptop anyway.

Larry said...

Sounds like time to do an "Office Space" on it.

You probably have either a CPU, power supply or motherboard issue, (more likley one of the latter two) and from the sounds of it, either problem would blow your budget for this project. No use throwing good money after bad, so you may have to scrap the project.

kilgor said...

http://www.buy.com/retail/product.asp?sku=210251213&adid=17653&dcaid=17653

Pretty decent desktop for $269 delivered.

Mithras61 said...

No beeps means you aren't getting far enough into boot to give you video. Again, if this thing is like most older Compaq systems, you have a riser card that MUST be seated securely to allow the system to complete its power on self test. Usually, the entire thing is part of a cage that slides out of the system once a couple latches are released. You should remove it and re-seat it, making sure you press it firmly into place (I've fixed more "it won't boot up" problems on old Compaq systems this way).

If that doesn't work, and considering the fact that Compaqs are notoriously proprietary in their fundamental components, you are probably looking at replacing rather than repairing this system.

Don Gwinn said...

I don't *think* this system uses a riser card. To be honest, I'm not sure what that would be, but it sounds like some sort of in-between, like an adapter fitted between components and the motherboard. There's nothing like that.

Yes, the case consists of a metal space-frame apparently designed by Volvo engineers to withstand 30mph collisions, which has to be slid out of the metal box outside case (with cheesy, curvy beige plastic in front.) There's no room to work whatsoever, and I'll be glad to be rid of it.

I learned about Compaq parts when I owned one of the 500-series all-in-ones before this. There was no way to upgrade anything, even by putting a new motherboard into the case. But that one worked without a glitch for five years, got me online, and I figured Compaq must be quality.

I was wrong.

This one led me a merry search a few years ago when the power supply failed. I thought I'd upgrade while I was at it, but of course the Compaq power supply had to be smaller than standard, plus it had to be snuggled into an elaborate steel box inside the case, just in case of . . . I don't know, maybe tornado? I did eventually find a power supply, but I paid more dollars for less power.

Larry said...

A riser board would plug edge-on into the motherboard, and then other cards (PCI cards) would plug into that, so that they would be parallel to the motherboard.

In several models of Compaq desktop, that steel frame inside has a lever handle which locks into place to firmly secure the riser board-motherboard connection, or to pry them apart.

Kilgor said...

The previous computer I linked to is now sold out.

Here's a much more powerful computer than the previous one I linked to for $229 delivered. At that price, is it worth fixing and old one?

http://www.buy.com/retail/product.asp?sku=210191647&adid=17654&dcaid=17654

chuckr44 said...

The newer video cards pull quite a lot of power, and you mentioned your power supply was undersized.

Could be the video card is not just getting enough power. The other solutions here are also valid.

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