Old PC won't POST

[JorgeA]

I have an ancient Vista-era PC that's used for contributing to a distributed computing project.

Today I went to check on its progress and switched the monitor to its input. To my surprise, there was no video being fed to the monitor. (The light on the power switch was shining.) Jiggling the mouse and tapping keys on the keyboard didn't do anything.

So I switched the power off and tried to reboot. The green light on the power switch came back on, but after a feeble spinning-up of the HDD, nothing further happened. The case fan and the CPU fan did spin up. However, pressing the button to open the DVD drive (I wanted to see if I could boot into a Linux live CD) didn't do anything, the drive wouldn't come open. I tried switching the video output from the GPU to the integrated graphics, but this didn't work either.

Tonight I had some time to try again. I disconnected all cables, pressed the power button to drain any remaining electricity in the system, dusted the inside of the case, and made sure that there were no loose connections inside. Then I re-connected the cables and tried to reboot. This time, the fans were still spinning up, but the green light on the power switch wasn't coming on.

I noticed that the fans started up, ran for a few seconds, and then stopped running, at which point they started running again. Now I couldn't turn them off by pressing the power switch and had to use the I/O button on the PSU to turn the machine off.

Can anybody offer ideas, based on their own experience, as to what might be going on here? My main suspects are (1) the power switch, (2) the PSU, and (3) the motherboard.

What do you think? I can provide make & model details if it might help. FWIW, the computer dates from 2008.

In case anybody's tempted to say it -- yes, I know that the sensible thing is probably to just dump the machine. But this has become a whodunit and I'm curious to find the culprit.

 

[PHolder]

It definitely sounds like a power problem. If you had a loaner PSU that would be the most likely thing to try next. Another thing to check is the capacitors on the motherboard--look for any with leaks or suspicious bulges.

 

[sttngs1]

I have an old HP desktop about that vintage with what sounds like the same sort of issue. I would disconnect as many devices as possible ( cd drive, monitor , hdds, etc). See if POST works then. Mine then did the POST beeps and manual said try different memory. Did that and rebooted. Different beeps said power supply not putting out 12 vdc. Bought used pwr supply and no beeps. Reconnected all devices and good to go. Good luck.

 

[cschuber]

This looks like a hard hang of sorts. It could be anything. Try removing all the RAM except one DIMM. Try booting it. If it boots, power off and insert another. Do this until it won't boot.

If the first stick of RAM doesn't work try the next and so on.

If none of the RAM work, the problem must be either MB or CPU. Try to find a replacement CPU. If that fails it's the MB.

Been there done that a few times. Usually it was RAM, sometimes CPU, as I've updated old machines with used CPUs, some worked others not.

Swapping RAM doesn't cost you anything. If you suspect CPU it's probably not worth the time or money to replace the CPU, unless you can get a used CPU for very cheap. I've found used CPUs for as little as $5. In that case, if you like to tinker it may be worth your while.

Replacing the MB is another matter. If the rest of the machine is fine a used MB with CPU and RAM may be the affordable option. It just depends on how much time and money you're willing put into this. It may be a cheap option or it may be small amount of money spent on nothing.

Older machines make excellent firewalls and routers. A firewall doesn't need a lot of horsepower.

 

[AlanD]

Can anybody offer ideas, based on their own experience, as to what might be going on here? My main suspects are (1) the power switch, (2) the PSU, and (3) the motherboard.

You can check the power switch easily. Follow the leads from the case front back to the motherboard and remove them from the pin connectors. Then just momentarily short out those two pins, e.g. with a screwdriver, the system should start if the switch is the problem.

I think the most likely problem is the PSU. It sounds like one voltage has gone down. That would explain why the fans are working )5v line) but the drives are not (12v supply). You might be lucky if you have spare power leads and can swap the connections on the drives for unused ones, they might be on a different rail. Otherwise, I bought a simple power tester off the net years ago. It allows you to test each type of connection in turn, e.g. Molex, 24pin, 6 pin, 8 pin, SATA etc. For example: https://www.ebay.co.uk/itm/315702414286

 

[JorgeA]

Many thanks for all the ideas!

It looks like I have some work (and buying) to do. I'll report back when I have some results.

Much appreciated!!

 

[PHolder]

It may be strange, but one other thing might be that the CMOS battery needs to be replaced. You wouldn't think it failing would cause POST issues, but if it's old enough, it'd be worth replacing anyway, and removing it will reset the CMOS for sure, which might be helpful as well.

 

[SeanBZA]

Yes had issues with flat CMOS batteries, so first of all replace the PSU with a known good one ( very cheap to get new as well, under $20 by me for a 200W mystery brand one) along with the CMOS battery, typically a CR2032 primary lithium cell. then remove all memory, and try the power button, you should get some mournful beeps from the computer if the processor and BIOS, along with north and south bridge, are working. Then insert the memory ( power off, and power cord unplugged, with you touching the metal case to remove static charge on you first, which you need to do before removing them or the PSU in the first place) and you should get a post. If not motherboard is dead.

I have that at the moment, lightning strike near me, which took out the south bridge, the keyboard, the wireless mouse, a USB hub, the nice HP Laserjet P1102 printer I had, and the APC UPS they all were plugged in to, plus a 4 port cheap switch I used for plugging in other devices. bit expensive to replace all that, though luckily the 2 HDD in the computer survived unscathed, so the new to me computer got the one, and the boot drive was replaced with a SSD to get faster response over the old 2.5in 500g drive.

 

[JorgeA]

All right, I had the chance to try a couple of the suggestions. Here's an update.

• Changed out the CMOS coin battery. The battery tester said it was dead as a doornail. But after replacing the battery, the PC still won't POST.
• So then I inspected the capacitors on the mobo. Here's what I found:

  https://imgur.com/a/K4qRDLd

  (Hoping the link works.) The capacitor in the middle near the upper edge of the photo has some orange gunk on the top. There are a couple more like this, but this is the worst-looking one.

Would it be fair to say that the capacitors need replacing and that everything else may be OK? If they need replacing, then I'll have to take the PC to a computer shop, as I don't have soldering equipment and I'm all thumbs when it comes to this sort of thing anyway.

 

[JorgeA]

I have that at the moment, lightning strike near me, which took out the south bridge, the keyboard, the wireless mouse, a USB hub, the nice HP Laserjet P1102 printer I had, and the APC UPS they all were plugged in to, plus a 4 port cheap switch I used for plugging in other devices.

Ouch!!

I'm holding your recommended procedure in reserve pending opinions on the capacitors as reported just above.

 

[DanR]

Would it be fair to say that the capacitors need replacing

Yes! Absolutely! Those caps have failed. They have lost dielectric. As a result their capacitance values have changed and are no longer appropriate for the circuits they are in.

and that everything else may be OK?

When / Where will the next (still normal looking) cap fail?

Presumably (typically) other components are unaffected by the failed caps.

 

[JorgeA]

When / Where will the next (still normal looking) cap fail?

From your question, I get the sense that it would be better to have the shop go ahead and replace all the capacitors and not just the ones that have failed?

 

[DanR]

From your question, I get the sense that it would be better to have the shop go ahead and replace all the capacitors and not just the ones that have failed?

Yes. Other failures are almost certain to occur. So you could be returning to the shop periodically as additional caps fail. That said, some may never fail. It's an unknown. Cost may be a factor to consider?

 

[dg1261]

JorgeA,

Those electrolytic capacitors on your motherboard are designed to stabilize the 5V and 12V power to various parts of the board. If one or more fails, the supplied voltage will become unstable and the various semiconductors around them won't function properly.

Of the 5 electrolytics shown in your photo, I would change the three black caps. The one at top center has clearly failed, and the one on the left edge of the photo is also bulging and will soon fail. It's hard to tell from this angle, but the third one (just below the top center cap) also appears to be starting to bulge a little. That one is not in imminent danger of failing, but given enough time it probably will, so since you're replacing the other two you may as well replace that one, too.

The two brown caps (along the left edge of the photo) appear to be good. I would not replace those.

Beware that there may be other electrolytics not shown in your photo. Some may be hidden under shrouds or even under the fan/heatsink assembly.

FWIW, I have a video (link here) illustrating one of my recapping projects, which you may find of interest to get an idea of what's involved.

 

[sttngs1]

Very much looks like capacitor graveyard. It would definitely cause all kinds of issues even if it did POST. Whomever does the repairs should examine / test the others as well. Would recommend not doing it unless the tools and knowledge (reverse connected electrolytics make a big boom , etc) are available.

 

[AlanD]

I would check the costs of replacing those and possibly other components against the cost of a replacement motherboard. You may be able to pick one up very cheaply on eBay or similar.

 

[JorgeA]

Once again, thank you very much for all these replies and ideas!

Looking around the motherboard, there are four of those black capacitors, and none of them looks healthy. The other kinds all look OK, FWIW.

@dg1261 's video leaves no doubt that the recapping project is way above my pay grade. I've replaced motherboards and CPUs before, but capacitors are a whole different ballgame.

I may call the computer repair shop for an estimate, but the suggestion by @AlanD to find a replacement motherboard seems the most practical for my skill level. Amazingly (or maybe not), there are many of those IPIEL-LA mobos on eBay for the HP dx7500 selling for under $50. I can handle unscrewing things and screwing them back in, and on top of that it's bound to cost less than paying a technician to replace capacitors.

 

[JorgeA]

UPDATE: The replacement motherboard has arrived. I've checked the capacitors on it and they look good.

The "new" mobo came with its own CMOS battery, 4GB RAM, and CPU + cooler already (or still) on it. I cleaned out the cooler fan (it was pretty dirty), and changed out the thermal paste on the CPU as well as the CMOS battery.

Tonight I installed the motherboard and connected it. Pressed the power switch -- and nothing happened. It didn't light up. The fans aren't running and the HDD isn't doing anything.

Now I'm suspecting the PSU. Not that the mobo didn't need changing anyway, considering the condition of the capacitors. Unless somebody has a better idea, I'm going ahead with the procedure that @SeanBZA proposed, starting with the PSU.