s said:
Thanks again for the reply and great explanation.
Can the power input jack get damaged due to voltage fluctuations I
faced?
No. Typically a power jack is damaged by mechanical forces.
Such as tripping on the cord and forcefully pulling the
plug out. That can break the solder connections where the
jack is fastened to the motherboard.
And, how can I explain that during the power outage(and when
power was restored) it was fine and now it is having issues?
A good question. I don't have an answer.
Could the damage been done at that point which is showing up now?
It could, but as you explained yourself, the fact that the machine
worked after the failure, but failed to start later, is a bit
strange and not a coincidence.
Also, doesn't an adapter protect the laptop from such voltage spikes?
Not in any absolute sense. Even a UPS equipped with surge protection
devices, is not always able to prevent problems at its output. The
adapter on the laptop has an emphasis on portability and light
weight, so may not contain all the circuitry the owner would hope
for. For example, some seem to have poor hold-up time, the ability
to resist a short (16 millisecond) power outage.
Was my mistake not using a surge protector or voltage stabilizer?
Every location has its own set of conditions. I used to work at a
place, where there were short outages every day. The company ended
up buying a UPS for every employee, so no work would be lost. Other
locations may have clean power. Personally, I use a UPS and a surge
protection strip where I am now, and have only had one expensive
monitor damaged, even with that protection. There are no certainties
with electricity.
And if the jack is damaged could that prevent starting of the
laptop even from battery?
That is the part of the circuit that I need a schematic for. There
should be some transistors or MOSFETs in the path, to switch the adapter
or the battery. I don't think there are any relays. You would think,
if the battery still has a charge, that the circuit would still operate.
So something is wrong with whatever supervises these functions, and
that is the part I don't have any diagrams for. I've tried to find
chip specifications for power management chips, but wasn't successful
at finding anything for a laptop. As with many high tech things, in
order to find answers, you have to use the right terminology, and
so far, I haven't succeeded at figuring out what they might call
the function.
The problem is here in India where I live such components are pricey
and it is hard to obtain
a good quality one(coupled with the fact nearly all local shops have a
no-return policy).
If the battery has a charge, disconnect the AC adapter, and test the
laptop again. If it won't start, then the adapter is not preventing it.
How can I test if the switch has failed or not? I recall it pressing
it too hard when
my monitor did not start up in the first time a few weeks back. Could
that have caused
some damage which is showing up now? If the switch is damaged can it
be replaced(and if so how
difficult/expensive it might be)?
Did the switch work, after you pressed it too hard ? How many times
did it work successfully after that event ? I would think, it is not
a coincidence, that you've had a problem after a power failure, and
that is more likely to be the source of the stress.
Ideally, to test the switch fully, you would disconnect it from the
circuit. But since it is part of a logic circuit, in this case it
is probably sufficient to monitor the voltage on the non-grounded
end of the switch, and see that there is a full logic swing. This
is an example of a typical interface. The switch type is "momentary
contact", and would normally be open circuit. (On a desktop computer,
two of these circuits are used, one for "power" and one for "reset".)
The resistor is a "pullup resistor", and limits the current flow when
the switch is closed. The signal going to the logic circuit, can then have
two voltage values, either V+ or zero volts. If you saw intermediate
values, like 1/2 * V, then you would suspect a problem. The signal
should be binary, and have two well defined states.
V+
|
resistor
|
+---------------> to logic circuit
| Voltage = V+ when user is not pressing the button
x Voltage = zero volts, when user presses the burron
\
x
|
Ground
So, my monitor not starting up initially indicated power was not
going to the LCD panel the first time I powered it or something else?
To me, that indicates that the inverter did not start for some
reason. Some inverters have a signal that controls the intensity,
and if that signal said "zero intensity" then perhaps the inverter
would not start. So perhaps some other part of the laptop could
have done that. The function could be partially controlled
by a power supervisor circuit, that decides when the inverter
should be turned on.
Would a better idea be to show it to a service center, though I doubt
how much they can help and if
I can afford even their examination charges(they are around 5000rs or
100$ just to determine what is wrong
with your machine)
Even here, there are certain services which we refer to as
"highway robbery". In fact, some laptop repair facilities
here, charge $200 to "look at it", without fixing anything.
So even the people here, think twice before approaching a
repair facility. By comparison, if I take my car to a mechanic,
he might charge $30 to $60 for a simple diagnosis (if the car
had to be extensively disassembled, it would cost more). So
laptop repair is priced above what you would expect.
I see no evidence to suggest that the laptop repair people are
skilled. Many times, a poster here will say "they told me it
needs a new motherboard". Since that is essentially all the
important working parts inside, they can blindly tell the customers
that, perhaps without even opening up the unit.
By comparison, people who work in TV repair shops, know a lot
about the circuits they work on. They work at the component level,
and can repair things without replacing the entire TV. I suspect
laptop repair, requires less skill, if all repairs mean
"replacing the motherboard". I don't even think the average
repair facility (like a Dell authorized one) would solder the
power jack if it was loose. They're replace the entire
motherboard instead.
So the treatment you would receive at your repair facility,
would be just as poor as the treatment we get.
Can the adapter problem prevent the laptop from starting even from
battery?
Disconnect the adapter and test with the battery. You say the
battery is still charged, so that should be a good test. If
it still won't start, then the problem is more likely to
be inside the laptop.
And, can
motherboards fail due to voltage spikes(after the spike period has
passed like mine where it was
working fine when the power failed and came back and now giving me
issues)?
THANKS A LOT for your responses and time. I am indeed grateful.
I think the entire sequence of events has significance. But because
I don't know how the power supervision circuit works, I cannot say
if there is a latent failure mechanism possible or not. I doubt
it just ran long enough, to die on the next restart. Maybe the
circuit thinks the computer is still running for example, and is
not following the correct startup sequence. I'd suggest removing
the CMOS battery, if I thought it was tied into that circuit, but
I don't think it is.
The power supervisor should be reset, when both the main battery
is pulled, and the adapter is disconnected. Leave the battery
out for an hour, so any charge inside has drained, just to be
on the safe side. After that, put the battery back, and try it.
If it won't start, I don't see what else can be tried externally,
so you'd need to trace where the power goes inside the thing.
I've tried tracing some circuits on a desktop motherboard, and
it takes hours to do it, for even the simplest functions. That
is why a schematic is so important, for efficient debugging. I
have fixed things without a schematic, but it isn't an easy
or a sure thing.
Paul
