Archived from groups: alt.comp.hardware.pc-homebuilt (
More info?)
chris wrote:
> Thanks for the advice Dave -
> I have since investigated further and after dismantling the case and got
> access to the switches found that by pressing the power on switch directly
> ( i.e. not via the external case buttons) the power on LED flickers briefly
> and then goes out - if I repeat the process the light doesn't even flicker
> with the power remaining connected - (and the Pc doesn't acutally power up)
> . I have swapped the PSU and lead with a known working one and the same
> happens - thus ruling out any PSU issues.
> In summary the power on LED only lights after the power has been connected
> for the first time and the PC doesn't power up - subsequent power on
> attmepts don't even result in the LEd flicerking unless the power supply is
> disconnected and reconnected.
Has it EVER powered up? Because that sounds like a classic over-current
shutdown, meaning a defective component somewhere.
If something pulls too much current (like a defective CPU, defective
motherboard, defective hard drive, etc.) the PSU will go into an
over-current shutdown and it takes cycling the mains power off to reset the
over current protection circuitry.
>
> At first I susepcted a blown fuse but the this appears not to be the case
> as the process is repeatable.
>
> Do you think this might be a switch problem or something more fundamental
> ? - unfortunately I don't know the background to this PC ( why it was being
> discarded) but it seems worth saving i.e. PII processor full set of memory
> and a reasonable hard drive)
Well, it may have been discarded because it wasn't working.
The thing that confuses me is you originally said 'once in 50 tries'.
What's the maker, model, motherboard, processor (as in WHICH P-II)?
And what was the 'known working' PSU? Just because it works in another
system doesn't mean it has enough power to run that one, whatever it is. I
mean, I can't say with no information on what they are.
If it's an over-current shutdown the question is what's causing it. I'd
strip it to bare bones and try to find what's causing the short. Unplug all
the IDE devices, hard drive, CD ROMs, etc. Unplug the floppy. Remove all
but one stick of RAM. Remove all PCI cards, leaving only the video adapter
and see if it'll power up. If not, pull the remaining memory and video
card. See if power will stay on. If not, remove the CPU and see if power
will stay on. It obviously won't *boot* without memory, video, and CPU but
we're just trying to see if the PSU will stay on, looking for the short.
If you get to where it'll stay on then put components back in, one by one,
till it again fails to power up and that one is likely to be the culprit.
Hopefully at least the motherboard alone will power up (if it's the
processor, P-II processors are very cheap these days. 11 bucks for a 450 at
www.starmicro.net)
>
> Thanks
> Chris
>
>
> "David Maynard" <dNOTmayn@ev1.net> wrote in message
> news:10tibp8agjls3f3@corp.supernews.com...
>
>>chris wrote:
>>
>>
>>>Hi,
>>>my wife recently aquired an oldish ex work PC which I would like to reuse
>>>for our kids as the spec is still resonable and it has a fiar amount of
>>>memory /disk - however the problem is the power on and reset switches on
>>>the main case. They only work perhaps once in 50 or so times
>>
>>What are the symptoms, other than it not powering on. I mean, do the
>>switches 'stick' in one position or the other, or not move at all, or move
>>but no 'click', or what?
>>
>>Look inside the case and see how they're mounted. Are they simply loose?
>>Is the mounting bracket broken off the front bezel support?
>>
>>What I mean is, it may be possible to simply fix the ones that are there.
>>
>>
>>>so I wondered if there was a way of replacing these
>>
>>Yes, they can be replaced but it's not easy to describe in text because
>>you're unlikely to find some place that sells a 'direct replacement' so
>>it's a matter of looking at them and finding something close enough to
>>fit, and that depends on being passingly familiar with typical switches
>>and perhaps some ingenuity in mating them to the existing brackets inside.
>>If it's a *simple* one it might simply be a round shaft, momentary, switch
>>screwed into a flat bracket behind the plastic pushbutton and another
>>'standard' round shaft, momentary, switch could be put in the same hole,
>>perhaps using the back nut to adjust how far/close to the plastic plunger
>>it is so it depresses and releases properly.
>>
>>The generic solution is to buy a 'normal' pushbutton switch from some
>>generic supplier, Like radio Shack, and simply drill a couple of new,
>>correct size, holes in the front bezel, mount the new 'standard' switches
>>and move the power and reset wires to them. That means snipping the wires
>>off the old switches and soldering them to the new ones.
>>
>>
>>>or just bypassing the switches and hardwiring and using the main PSU
>>>on/off switch to power the PC?
>>
>>Well, there's not really anything to 'bypass'. Wiring the power switch
>>permanently 'on' would cause the computer to turn itself right back off
>>after the 6 seconds, or so, "hold me down to power off' timeout and
>>'bypassing' the reset switch is "disconnect it," but since it don't work
>>anyway it's already 'disconnected'.
>>
>>If the BIOS power settings can be set to always power on after a power
>>failure then you might be able to cycle the rear switch to turn it on but
>>that's really a kludge.
>>
>>
>>
>>>I'm not sure what effect taking out these switches would have.
>>>
>>>Any ideas appreciated -
>>>
>>>TIA
>>>Chris
>>>
>>>
>>
>
>