Futher laptop power question

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Thanks all for your previous answers but I thought I'd start this new
thread instead of carrying on the previous one as I wrote the earlier
description of the fault from memory and having just replicated the error
again here is a better description from which you might be able to work:

So, using the laptop ... dumdeedum.... for an hour this time. Then laptop
completely powers down, not even any flashing LEDs to indicate power
coming in from the AC (battery not in at time of use so irrelevant).
However the indicator LED on the power supply is still on. The laptop
will not power on now until it has 'rested' a while, presumably until it
or the power supply cools. It will then work as normal, until the error
occurs again. What does this indicate? Remember no lit LEDs on laptop and
power supply LED on the actual brick is still lit.

Now, I know this seems like a laptop issue rather than the PSU but there
is no obvious issue with the laptop other than this and the PSU on the
other hand does get very hot so it may well be a the cooling of the PSU
which is the factor. Not using the machine for particularly instensive
tasks when this happens- web browsing and playing an mp3 maybe. Probably
30/40% cpu usage.

Any further insights?


Re: Futher laptop power question

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Maybe your CPU is overheating .. It's very common in laptops, even if it is
clean of dust, all it takes is to cover the CPU air intake and it can
overheat. Most computers shutdown to prevent damage when the CPU hit a
certain temperature. Observe the temperatures with speedfan:

Re: Futher laptop power question

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Fan broken?  Not so likely, but still.   It goes on and off I think,
depending on temp.
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Re: Futher laptop power question

Keiron wrote:
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"the PSU on the other hand does get very hot"

There's your clue. If the new adapter is getting very hot and
shutting down after an hour, it could be the adapter is protecting

Now, you need to find out, exactly how much power the laptop is using.

It could be, the laptop is using excessive power. Consider for a moment,
the history of your computer. At one time, it had the "original" adapter.
Did the original adapter die, because of a frayed cord or broken
connector ? Or did it in fact die, because it overheated like the
replacement you're using now ? That would tell you the laptop
is the root cause of your problem.

You need some way, to measure the current flow, to see whether everything
is operating the way it should.

Will the laptop operate without the battery present, and the adapter
plugged in ? If so, then you would know it isn't the battery charging
circuit which is causing the overheat on the adapter.

Perhaps the power adapter is being asked to charge the battery, and
run the computer, at the same time, and the combined load is too much.
That implies the battery charging attempt is drawing more current
than is normal for the charging circuit.

If I was going to measure the current flow from the adapter, I'd use
my clamp-on DC ammeter. I would need a male to female, barrel connector
equipped adapter cable, because my clamp-on ammeter can only work,
if one conductor can be encased in the jaws. (I could split the wires
with a hobby knife, but that is making a mess of the cable. Most
people wouldn't like that.)

You can see in this sample photo, the user has an adapter cable, with the
two wires split, such that the jaws of the ammeter fit around just one
wire. The ammeter detects current flow, via the magnetic field associated
with it. I have a meter like that, which can measure both DC and AC
currents (internal Hall probe detector), and that is how I check current flow.


(Mine looks like this model, but is made by another company - approx $300 or so.
  It costs a lot more than a hardware store multimeter would.)


When you buy an adapter, it has a power rating. Say the adapter was
65W and supplied 19V.  Dividing 65W by 19V, gives the max current
in amps. That would be about 3.4 amps. I would take your laptop, in
its about-to-overheat state, measure the current and compare the
value to 3.4 amps. If higher than 3.4 amps, we know the laptop
is the problem. If lower than 3.4 amps, and still shutting down,
the adapter is substandard, and not living up to its spec.

You need to find someone with an ammeter, and an adapter cable,
to make the measurement. You can make your own adapter cable.
You can even use a conventional multimeter, on the amps range,
since in the process of making an adapter cable, you might as
well wire in the multimeter. The advantage of a clamp-on
ammeter, is you don't need to wire it into the circuit. The
clamp-on ammeter is a "non-contact" measurement device.

    |         |----------------------------> Laptop
    | Adapter |                              2 wire
    |         |---------+         +--------> Input
    +---------+         |         |
                      |  Multimeter |
                      | 10 amps max |
                      |    Scale    |

Switch mode power supplies, inside wall adapters, cannot afford to get
hot. With a plastic casing, there is no where for heat to be dissipated.
Thus, the adapter must be very efficient, so there won't be a lot of
waste heat. That being said, the power rating of the adapter,
does give you some idea of its limits, and if you're connecting a
65W adapter to a 95W laptop, then again, you'd have a problem on
your hands because of the "mismatch of expectations".

My guess is, your problem is related to charging the battery.
That's all I can suggest at the moment.


Re: Futher laptop power question

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Almost guaranteed to be an overheating issue.  Make sure the laptop is on
a hard surface, not a carpet or blanket, so their is enough space under
the laptop (kept up by it's tiny little feet), for proper airflow.

Regards, Dave Hodgins

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Re: Futher laptop power question

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It could be a simple problem - the wire that runs from the power 'brick' to
the laptop might be damaged. This can easily happen over time with laptops
as the wire is bundled up, then unwrapped repeatedly and the connections
inside can wear down and fail. Did it turn off when you moved something?
Make sure the laptop is sitting flat on a desk and the wire can't move (you
could even tape it to the desk to be sure) and test again.

Another thing to try (I seem to remember you asking about this anyway) is to
remove the battery from the laptop and run just on mains. This will reduce
the load on the power source as the battery won't be permanently charging.
It would also rule out a damaged charging circuit causing the problem

What is the power supply (to the house) like - does it occasionally flicker
or fail for a moment - this could cause the problem, but again this is
unlikely to affect a laptop as the battery would keep it going for a few
seconds at worst.

I don't think its hardware inside the laptop. if the CPU were overheating,
the laptop would throttle back the CPU speed and run at a very very slow
speed and make warning beeps and noises, but it wouldn't just turn off like
that without other symptoms and warnings - you could install and run
Speedfan to find out though (its a small app, free and easy to find -
google). If the memory is failing then you would get random restarts and
crashes, but not a power off. The motherboard could be failing, but I
suspect that you would see similar symptoms to the memory failling - crashes
and restart, but not a refusal to come back on.

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