Re: 2 PCs not starting up properly nor shutting down
- From: w_tom <w_tom1@xxxxxxx>
- Date: Mon, 19 Nov 2007 17:36:03 -0800 (PST)
On Nov 18, 10:16 pm, Erik <E...@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Thanks, that sounds like a good explanation.
I will look for shorts tomorrow, but I'm afraid that may be a long shot.
Remember, I had two PCs fail, and what are the chances that both of them
failed because of a short.
A short is not a likely reason for damage. Short typically only
creates a temporary failure. Digital IC outputs can be completely
shorted to ground and still not be damaged as was standard even before
CMOS transistors - when ICs were made with bipolar transistors.
Permanent failures are created by manufacturing defects that may
appear months or years later, static electric discharges, and other
human mistakes such as removing or disconnecting something with power
cord still connected to AC. Heat, shorts, and other things so often
blamed in myths typically do not create permanent damage.
If this diagnosis had proceeded without part removal or swapping,
then a list of possible problems would have been significantly
limited. Symptoms observed before complete failure occurred would
have merit. Currently, the motherboard could have two or more
problems since part swapping has a bad habit of creating new problems.
With so many additional possibilities, then the original intermittent
symptoms provide too little useful information.
Sometimes a defective part tested elsewhere can cause that
elsewhere machine to become defective. When constructing
$multimillion custom computer controlled workstations, part swapping
between machines to find a problem was forbodden - in one case almost
causing employment termination. Once one defect becomes two, then
the problem becomes exponentially more complex.
Same procedure should be executed on the second machine without
swapping or disconnecting any parts. IOW, like in CSI, "follow the
evidence". And do not shotgun. Perform the same diagnostic procedure
on the second machine.
Returning to the original machine. CPU would not execute BIOS. But
CPU will not even clock a single machine cycle until the power supply
controller issues a command that says, "OK - ready to work". Power
supply controller is known to have at least one defective. Quite
possible is that motherboard failure is a single point problem limited
to power supply controller. Therefore CPU also would never get
permission to execute software.
One step at a time for that first system. Replace motherboard
(which might mean a new CPU). Then establish that other components
are working by first confirming those power supply voltages are
correct. With correct voltages, then power supply system works -
something accomplished. With only motherboard, speaker, power switch,
CPU, power supply, and nothing else, then motherboard should beep.
Another accomplishment: CPU, some motherboard functions, etc are
working. Add memory and video controller. More accomplished if
BIOS displays a video message. Slowly removing everything from the
'unknown' state.
Repeat same for the second system. Slowly get each component or
subsystem moved to 'definitively good' or definitively' bad. Do as on
CSI - "follow the evidence". Break that massive unknown second
computer into components "definitively known good" or "definitively
bad". It may appear tedious. But each step or test means
accomplishment every time a component is removed from an "unknown"
state.
Break each computer down into parts, then analyze only each part to
get an answer that includes the word 'definitively'. IOW do to the
second computer what we did to the first.
.
- References:
- 2 PCs not starting up properly nor shutting down
- From: Erik
- RE: 2 PCs not starting up properly nor shutting down
- From: Andrew E.
- Re: 2 PCs not starting up properly nor shutting down
- From: w_tom
- Re: 2 PCs not starting up properly nor shutting down
- From: Erik
- Re: 2 PCs not starting up properly nor shutting down
- From: w_tom
- Re: 2 PCs not starting up properly nor shutting down
- From: Erik
- Re: 2 PCs not starting up properly nor shutting down
- From: w_tom
- Re: 2 PCs not starting up properly nor shutting down
- From: Erik
- Re: 2 PCs not starting up properly nor shutting down
- From: w_tom
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