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- HP Pavillion zv5000 Power issue
July 1, 2008, 5:42 pm
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I have an HP Pavillion zv5000 notebook computer. It's been fine for a
while, but now it won't turn on. I've done some research and I have
found that it may be the power jack that needs to be replaced? What
happens is that when I plug it in, the power light on the front just
blinks. When I go to press the power button the power light comes on
for about a second and then goes off. Therefore it won't power up.
Just wondering if anyone could shead some light on this issue. Let me
know, and all help is greatly appreciated!
Re: HP Pavillion zv5000 Power issue
The blinking could be because the adapter has detected an overload
condition. The adapter itself could be defective. Or the laptop
may be drawing more current than it is supposed to.
If it was my laptop (because I own test equipment) I would
1) Cut adapter cable, in order to make a DC current flow
measurement. Plug in adapter. Set digital multimeter to
detect peak current flow. If the peak current flow exceeds
adapter rating, then the laptop is overloading the adapter.
A multimeter with peak detection is required, because the
adapter will shut off in 35 to 50 milliseconds, before a
conventional measurement can be completed.
2) Do a load test on the adapter. (Connect the adapter to a load resistor,
and not to the laptop at all.) If the adapter was rated at
19V and 3A, I would use a 6.33 ohm resistor. The resistor
would need a power rating of I*I*R or V*V/R or 57 watts.
The resistor will get very hot, so I would blow a fan over
it, or connect a heatsink to the resistor. It requires some
knowledge of Ohms law, how to put resistors in series or
parallel, to get the desired value. I would also try a
couple different values of loading, like a bit less than
full load, to see if the adapter can work at all. If the
adapter goes off, then it has detected an overload. It should
only overload, if an actual overload was present (i.e. draw
more than the 3 amps in my example).
Example of adjustable resistor.
A fixed resistor that bolts to a heatsink.
Generally, a power jack failure leads to no power flow. The
adapter should not overload, and if there is a LED on the
adapter, it should remain lit and not blink. On the other
hand, if the power jack is still good, the blinking of
the adapter is because it has detected an overload. If
the adapter is not plugged into the laptop, and the
LED stays on, then you know that the blinking behavior
is load related. The overload could be present, because
in fact, the power jack is still making good connections,
and the overload is inside the laptop.
Based on the information you have provided so far, I think
the plug and jack are OK. Examine the cord of the adapter,
near where the barrel connector is attached on the end.
Look for broken or frayed wires, as they could be what is
causing the adapter to blink. Sometimes, the wear and
tear on wire and connector, causes a short, and the
frayed wire could be inside the plug assembly on the
end of the cable.
If the adapter is OK, and capable of delivering full load,
then something inside the laptop may be responsible for the
The question is, will you pay $200.00 for someone to
"look at it" ? That is the joy of owning a laptop.
If I had a reference schematic for a laptop, I'd be able
to make more suggestions, but to date, I've never had
access to a schematic. I'd like to understand how the
input circuitry is set up, to make it easier to
predict what can happen. Like whether a dead battery
could cause the symptoms.
Re: HP Pavillion zv5000 Power issue
Rather than cutting the cable, it might be more desirable to
open the power brick case, desolder the wire from the PCB so
the meter is between PCB trace and end of wire... that way
the wire can be resoldered when the measurement is finished
without having to repair the cable, plus if the AC-DC brick
has burnt marks or popped capacitors inside then opening it
may reveal such problems. Also with it open one can more
directly measure the output voltage while it's powering the
laptop. Main issue is of course that one must exercise
caution since the open ac-dc brick potentially exposes the
technician to live AC mains voltage.
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