PC powers on but DOS/Windows won't boot

flanree

When I power on my PC I hear the fans starting up but my monitor remains blank. The drives dont seem to startup at all. I get no DOS text or anything on screen and yet the power fans continue with no further progress. I have tried the Windows OS CD, it doesnt recognise and disc in there, tried a floppy boot disk, doesnt recognise that driver either. Any ideas?

Dublin_Gunner

So you get nothing displaying on the screen at all when you boot it up?

The video card may have died, the BIOS may need resetting, the screen may be damaged, or probably a number of other things too.

Does it make any beep sounds when it starts? Specifically, does it make beep sounds different to the ones it used to make?

Has anything changed in the PC at all, or did this just happen one day when you tried to turn it on as normal?

Skerries

how old is it that it has a floppy drive?

Sup08

Try open up the pc and make sure the ram is seated correctly in the slots and the HDD connections are all set tight.
As said before "are there any beeps when the power button is turned on?"
There should only be one short beep.
If there are anymore count them, by long and short. IE 3 short 1 long. Then post them back here.

flanree

Ah I forgot about the beeps! It doesn't beep at all when starting up now. It usually beeps twice I think at the DOS stage normally.

Torqay

The "DOS stage" is called POST screen.

First thing to do in a case like this: disconnect the power, press the power button a few times to discharge all components, then try again.

If that's to no avail, then reseat the memory modules and any addon cards.

flanree

Torqay wrote: »

The "DOS stage" is called POST screen.

First thing to do in a case like this: disconnect the power, press the power button a few times to discharge all components, then try again.

If that's to no avail, then reseat the memory modules and any addon cards.

By reseat the memory modules and any addon cards, do you mean just remove RAM, graphics cards etc from the board and put them back in?

Torqay

flanree wrote: »

By reseat the memory modules and any addon cards, do you mean just remove RAM, graphics cards etc from the board and put them back in?

Yep, that's wat I mean.

Or put a little bit of pressure on them to make sure they are seated properly in their slots.

flanree

It worked! took em out, stuck em back in and she booted up fine! Thanks very much!

Fergus

Motherboard capacitor failure.

Dublin_Gunner

Fergus wrote: »

Motherboard capacitor failure.

Seriously from the OP's description - how on earth did you come to that conclusion???

Especially considering depending on the Cap, it may make no noticeable difference whatsoever (especially if it got shorted after failure).

Fergus

Because PSU function is probably ok if it's responding to power up signal and fans are working, and no POST diagnostics or video output suggests the CPU is not bootstrapping at all.. and given no recent physical changes to the hardware, it implies something has just failed in place that is causing fundamental circuit instability.. so capacitors would be certainly something I'd check first. Heatsink failure is going to trigger thermal protection so not as likely to lead to total failure of the logic to start up.

Dublin_Gunner

Fergus wrote: »

Because PSU function is probably ok if it's responding to power up signal and fans are working,

That's completely wrong. PSU may be able to start up and supply enough power for fans, but ifs it on the way out may not be providing sufficient power for the rest of the system.

Fergus wrote: »

and no POST diagnostics or video output suggests the CPU is not bootstrapping at all..

Or the system speaker has not been fitted...

Fergus wrote: »

and given no recent physical changes to the hardware, it implies something has just failed in place that is causing fundamental circuit instability.. so capacitors would be certainly something I'd check first.

No, first thing I'd check is has anything come loose? (as was suggested above). Reseat everything and boot again, and then go through process of elimination to find the problem component, starting with a minimal build and adding components until failure to boot.

Fergus wrote: »

Heatsink failure is going to trigger thermal protection so not as likely to lead to total failure of the logic to start up.

WTH is heatsink failure? In all my years testing and building I've never once had anything that could be described as a catastrophic heatsink failure. Is this when it falls off or beams down to the surface?

As the components have to heat up to get to any thermal protection limit, heat could never be the cause of this issue.

You could even start the machine without a heatsink attached to the CPU at all and it would start the boot and POST processes until failure or thermal cut-off.

Looking for a blown Cap (or other failed discrete component) on the motherboard would be one of last things I'd look for in an instance such as this. It is FAR more likely to be something more simple.

However, if you should see a small puff of smoke or smell burning electronics...

Fergus

OK.. my apologies for being misleading.. I wasn't basing my conclusion on the OP: I actually spoke with flanree two weeks ago after the problem had re-occurred. As I result of that conversation, I ended up replacing the capacitors on the motherboard and the system is now stable.

Dublin_Gunner

Fergus wrote: »

OK.. my apologies for being misleading.. I wasn't basing my conclusion on the OP: I actually spoke with flanree two weeks ago after the problem had re-occurred. As I result of that conversation, I ended up replacing the capacitors on the motherboard and the system is now stable.

So you replaced all of the caps on flanree's motherboard?

Why then does he state merely re-seating the memory fixed it?

Sorry, but this seems all very confusing. And if it went to a case of replacing caps on a motherboard - the manufacturer would be getting the board for an RMA (unless its years old of course).

Fergus

The board was around 5-6 years old, and the PSU had been replaced previously.. so capacitor plague was a big suspect in my mind with the given symptoms.. and visual check showed OST brand caps with signs of venting. Given borderline components like that, I have a feeling the disconnect from the power and general associated cooling down, discharging, etc., while doing the reseating could have been enough to get it going again temporarily. Another machine I did a re-cap on recently was mostly just giving occasional hangs or windows exceptions but it had also failed to power up once or twice.. that one was being caused by the 3.3v rail caps.

I'd agree with you that blaming caps wouldn't make much sense on newer boards.