Hello!

A friend asked me to look at his laptop (I have 15+ experience in
assembling computers and home made repairs - but mostly desktops).
The laptop died during a night, it was ok in the evening and completely
dead the next morning. It's 15 months old HP Pavilion.
There was no power outage or thunderstorm that night.

Now the computer shows absolutely no symptoms of life. When I plug it
in nothing is happening, nothing on the screen, no humming, no
electronics or even a single led goes on. Nothing! I checked the power
supplier, used a spare one, on battery - still the same, dead.
Then I removed the battery, hdd, CD drive, both memory sticks and then
plugged it in - still no progress.

I haven't gotten further/deeper to the inside yet (my friend is still
considering going with HP service) so I'd like to ask you what other
diagnostic test I could use. Any ideas? Looks like it may be a power
related issue, but to confirm that I would have to remove the cover.

Could it be a dead LCD screen? But wouldn't all power functions
(battery charging, etc) work normally then?

I'd appreciate all hints you might have.

Thanks,
L.

No, it's not a dead LCD screen. If it was just the screen, the laptop
would actually start, and you could use it with an external monitor.

The laptop has a power light that simply indicates if it's getting
power. Since this is not on, you are most likely dealing with a
catastrophic power supply failure (catastrophic in terms of it's
consequences, but the cause could be as simple as a bad connector or
blown fuse). By "power supply" here, I mean the power supply inside the
laptop, not the external AC power supply.

Does the laptop work with a good, charged battery? [since the failure
occurred in the middle of the night while the laptop was turned on, the
battery, even if fully charged at the time, could have become fully
discharged keeping the laptop running after the failure occurred].

Unless the problem is grossly obvious and simple, the chances of your
being able to fix it near zero. And, unless the problem is grossly
obvious and simple, the "fix" is likely to be either a new power supply
(if it's a separate module inside the laptop ... which is uncommon) or,
most likely, a new motherboard. A new motherboard outside of warranty
is usually prohibitively expensive (may cost as much as a new computer,
$300 to $600 is typical).

But that's a good assessment of where you likely stand.



Luke wrote:
> Hello!
>
> A friend asked me to look at his laptop (I have 15+ experience in
> assembling computers and home made repairs - but mostly desktops).
> The laptop died during a night, it was ok in the evening and completely
> dead the next morning. It's 15 months old HP Pavilion.
> There was no power outage or thunderstorm that night.
>
> Now the computer shows absolutely no symptoms of life. When I plug it
> in nothing is happening, nothing on the screen, no humming, no
> electronics or even a single led goes on. Nothing! I checked the power
> supplier, used a spare one, on battery - still the same, dead.
> Then I removed the battery, hdd, CD drive, both memory sticks and then
> plugged it in - still no progress.
>
> I haven't gotten further/deeper to the inside yet (my friend is still
> considering going with HP service) so I'd like to ask you what other
> diagnostic test I could use. Any ideas? Looks like it may be a power
> related issue, but to confirm that I would have to remove the cover.
>
> Could it be a dead LCD screen? But wouldn't all power functions
> (battery charging, etc) work normally then?
>
> I'd appreciate all hints you might have.
>
> Thanks,
> L.
>

Luke wrote:

> A friend asked me to look at his laptop (I have 15+ experience in
> assembling computers and home made repairs - but mostly desktops).
> The laptop died during a night, it was ok in the evening and completely
> dead the next morning. It's 15 months old HP Pavilion.
> There was no power outage or thunderstorm that night.

This must be debugged from first principles.

1. See if the machine has a resettable system controller. Many portable
machines have a procedure to reset the system management controller in
case it crashes - very often (but not always) the procedure is: remove
AC and battery, press and hold power button for 10 seconds, reconnect
AC.
2. Measure voltage output from AC adapter. (Not likely to be the
problem).
3. Disassemble computer and start tracing back from the DC input.

Since it no longer starts up off either battery or AC, nor shows any
kind of charge indication when you plug it in, the problem is likely in
the DC/DC section and could be very challenging to debug. I would start
by plugging in the AC supply (leave battery out) and probing around the
board to see if you can find a 3.3V or 5V standby voltage. Also probe a
pin that is known to carry power (find a 74xx series or other
identifiable IC and use that as a test point) and see if you get a
wiggle on the power pin when you press the power button. If this is
present, then your problem might be in the system controller or the
DC/DC section. Hard to give generic advice here.

Of course, look through the machine for fuses. Most such devices would
be resettable polyfuses but it's definitely worth checking them.

Barry Watzman wrote:
> No, it's not a dead LCD screen. If it was just the screen, the laptop
> would actually start, and you could use it with an external monitor.

Thanks for this clarification. I've never dealt (knock on wood!) with
the broken LCD.

> Does the laptop work with a good, charged battery?

I wish I had a spare battery fitting this model. I'll ask my friends
around!

> Unless the problem is grossly obvious and simple, the chances of your
> being able to fix it near zero. And, unless the problem is grossly
> obvious and simple, the "fix" is likely to be either a new power supply
> (if it's a separate module inside the laptop ... which is uncommon) or,
> most likely, a new motherboard. A new motherboard outside of warranty
> is usually prohibitively expensive (may cost as much as a new computer,
> $300 to $600 is typical).

that's what I think too. Hopefully I'll be able to check the fuse and
if it doesn't help I'll recommend my friend selling parts (DVD, LCD) on
ebay. There is plenty of $500-600 new laptop deals around this time of
the year!

Thanks a lot!
L.

zwsdot...******.com wrote:
> This must be debugged from first principles.
>
> 1. See if the machine has a resettable system controller. Many portable
> machines have a procedure to reset the system management controller in
> case it crashes - very often (but not always) the procedure is: remove
> AC and battery, press and hold power button for 10 seconds, reconnect
> AC.

I'll check it out tonight!

> 2. Measure voltage output from AC adapter. (Not likely to be the
> problem).

AC adapter works fine with the other laptop so I don't think it's
broken.

> 3. Disassemble computer and start tracing back from the DC input.
>
> Since it no longer starts up off either battery or AC, nor shows any
> kind of charge indication when you plug it in, the problem is likely in
> the DC/DC section and could be very challenging to debug. I would start
> by plugging in the AC supply (leave battery out) and probing around the
> board to see if you can find a 3.3V or 5V standby voltage. Also probe a
> pin that is known to carry power (find a 74xx series or other
> identifiable IC and use that as a test point) and see if you get a
> wiggle on the power pin when you press the power button. If this is
> present, then your problem might be in the system controller or the
> DC/DC section. Hard to give generic advice here.
>
> Of course, look through the machine for fuses. Most such devices would
> be resettable polyfuses but it's definitely worth checking them.

Thanks for the detailed description! As soon as my friend gives me a
green light (he's dealing with HP service right now) to do this I'll
proceed!

L.

Re: "As soon as my friend gives me a green light (he's dealing with HP
service right now) to do this I'll proceed!"

To be very honest about it, from your own description of your experience
and also your questions ("could it be the LCD display?" when the power
light isn't even coming on), you have very little experience with laptops.

The reality is that if you ATTEMPT to even open up the laptop, you will
probably do further damage. Laptops are not just small desktops, they
are completely different animals in terms of how they need to be
serviced. Simple things like not knowing about flex cables and their
ZIF sockets can destroy a laptop, if you are even able to get the case
open to get that far. I don't know your knowledge or your capabilities,
but very generically, if you have neither laptop experience nor laptop
training, doing more damage is far more likely than successfully
repairing this problem, unless it's very simple.


Luke wrote:
> zwsdot...******.com wrote:
>> This must be debugged from first principles.
>>
>> 1. See if the machine has a resettable system controller. Many portable
>> machines have a procedure to reset the system management controller in
>> case it crashes - very often (but not always) the procedure is: remove
>> AC and battery, press and hold power button for 10 seconds, reconnect
>> AC.
>
> I'll check it out tonight!
>
>> 2. Measure voltage output from AC adapter. (Not likely to be the
>> problem).
>
> AC adapter works fine with the other laptop so I don't think it's
> broken.
>
>> 3. Disassemble computer and start tracing back from the DC input.
>>
>> Since it no longer starts up off either battery or AC, nor shows any
>> kind of charge indication when you plug it in, the problem is likely in
>> the DC/DC section and could be very challenging to debug. I would start
>> by plugging in the AC supply (leave battery out) and probing around the
>> board to see if you can find a 3.3V or 5V standby voltage. Also probe a
>> pin that is known to carry power (find a 74xx series or other
>> identifiable IC and use that as a test point) and see if you get a
>> wiggle on the power pin when you press the power button. If this is
>> present, then your problem might be in the system controller or the
>> DC/DC section. Hard to give generic advice here.
>>
>> Of course, look through the machine for fuses. Most such devices would
>> be resettable polyfuses but it's definitely worth checking them.
>
> Thanks for the detailed description! As soon as my friend gives me a
> green light (he's dealing with HP service right now) to do this I'll
> proceed!
>
> L.
>

Barry Watzman wrote:

> To be very honest about it, from your own description of your experience
> and also your questions ("could it be the LCD display?" when the power
> light isn't even coming on), you have very little experience with laptops.

I did disassemble/open laptops (as well as tv sets, cd drives, hard
drives, power suppliers, you name it) before. Your assumption based on
my questions is just totally wrong. I just never dealt with a broken
LCD screen and thought that this kind of symptoms (dead system) might
have occurred since they were programmed that way by a manufacturer.
When LCD is broken and your computer operates fine (you just see
nothing on the screen) you may still delete files and cause a lot of
damage!

L.

Luke wrote:

> Thanks for the detailed description! As soon as my friend gives me a
> green light (he's dealing with HP service right now) to do this I'll

Don't get his hopes up too high. Your chances of fixing this if it
isn't something simple (fuse, crashed controller) are not good. I'm
just telling you what I would do if I was, say, fixing a machine for
one of my wife's friends.

If you are doing this for pay at standard rates, it is practically
certain he would be better off buying a replacement motherboard (or
DC/DC board if it's separate on this model). If you are doing it pro
bono, I congratulate you on your generosity :)

zwsdot...******.com wrote:

>
> If you are doing this for pay at standard rates, it is practically
> certain he would be better off buying a replacement motherboard (or
> DC/DC board if it's separate on this model). If you are doing it pro
> bono, I congratulate you on your generosity :)

I have never charged my friends (not only close friends) for this kind
of work. I know that chances are relatively small, but we have nothing
to lose. Given the number of deals at this time of the year (in the US
$500-600 new laptops deals are easy to find) any $200-300 cost repair
just does not make sense.

Thanks!
L.