Odd power on issue

[MotzTech]

I'm having trouble with my personal gaming rig. Unfortunately I don't have spare parts to swap out to test everything, so I wanted to get some opinions.

When I first power the system on I don't get a video signal. No matter how long I let it run I don't get a signal. I have to forcefully power it off and back on several times before I get a video signal.

During the second or third power on I can hear what sounds like the fans slowing down and speeding back up. I have not been able to figure out which fan this is. Eventually one the third or fourth reset and power on, it boots up and everything works fine (or as fine as can be expected for 7 year old system).

I tested the RAM for an unrelated issue and it came back with a boatload of errors, but I tracked that down to what seems like a bad slot. Switching the ram so it did not use that slot fixed that issue. However I think this may be related.

I also tested all the hard drives, and they are fine. The issue occurs even if no hard drives are connected.

I installed a basic VGA video card to see if it output any type of signal when the main card didn't. It did not output anything. During gaming I don't see ANY performance issues with the card.

So I have narrowed it down to two things, a bad power supply or a bad motherboard. The power supply is a high wattage Antec,not something I keep around the shop.

The boot up issue makes me think motherboard, but everything works fine after it boots. Surely if the motherboard was going I would get all kinds of errors.

On the other hand, the fans slowing down like that make me think power supply. Which might explain why it boots up fine after it's be running for a bit and gets restarted.

What do you guys think? Sorry if I missed anything, been a long day but I wanted to submit this before I hit the hay.

 

[ohio_grad_06]

Sounds like board. If the psu were having problems it seems like the video card would have problems when you are gaming with your video card as that should put a load when you are gaming. Plus you have already had issues with the tan slot, so your board seems to have a history already.

 

[mraikes]

I've encountered failing capacitors in systems that old that created similar random boot issues. Until they got so bad they wouldn't boot at all.

 

[Moltuae]

Sounds like board. If the psu were having problems it seems like the video card would have problems when you are gaming with your video card as that should put a load when you are gaming. Plus you have already had issues with the tan slot, so your board seems to have a history already.

I dunno ... I wouldn't rule out the PSU. I've seen similar issues caused by faulty PSUs.

Most modern power supplies are of the switched-mode variety. Due to the way switched-mode power supplies generate and regulate the output voltages, there's a stabilisation period after power-on that ensures the output voltages are within the specified limits. A feedback circuit ensures that if any voltage does not meet the required specification, the related outputs are inhibited. In some cases this can result in power supply outputs intermittently not starting, due to borderline tolerance discrepancies. Under load, when the SM PSU is working harder, such discrepancies can actually become less significant as circuit impedances reduce.

The power supply is a high wattage Antec,not something I keep around the shop.

It's unlikely that the system requires anything like the wattage the PSU is rated at, certainly not when the system is relatively idle at least. A basic/generic 500W PSU should be more than good enough for diagnostic purposes. You could disconnect any non-essentials, like optical drives, to reduce the load further if necessary.

 

[B Trevathan]

Have you tested the monitor and cable, they do go bad also.

It sounds like a capacitor going bad somewhere, look very close around the CPU, Power connections and RAM slots. Do you see or smell any other burnt components?

After the first boot failure have you tried draining the flea power?

Have you tried booting with just the bare essentials, to just boot you don't need a HD, DVD, sound card, NIC or MODEM connected.

Do you have anything plugged in to the USB ports like a printer? Have you check the ports for damage?

 

[damitman]

7 year old system I have several around that age group
I would give it a good cleaning, air and alcohol, many annoying problems can arise from slightly dirty contacts. 91% alkie will clean the carbon buildup between contacts that we really cannot see, but I know it is there
a q-tip is a wonderful tool, in the skilled hands of a pro

clean and re-seat works wonders

 

[ComputerRepairTech]

So I have narrowed it down to two things, a bad power supply or a bad motherboard.

The boot up issue makes me think motherboard, but everything works fine after it boots. Surely if the motherboard was going I would get all kinds of errors.

On the other hand, the fans slowing down like that make me think power supply. Which might explain why it boots up fine after it's be running for a bit and gets restarted.

You won't know the answer until you test another psu. I've seen those symptoms in video cards, motherboards and psu's. The only thing you can safely be sure of is eventually the problem component isnt going to come back on ever again.

 

[MotzTech]

Well, after banging my head against this I decided to tear the whole thing down and rebuild it. Now everything is working fine. Still have no idea what caused it though.