Laptop wont power on.

[DLeonR]

Acer 7740 laptop working fine, turned it off, then after a couple of hours, I notice there is no blue light where the power cord is plugged into. When press the power button, nothing happens. I can't figure what happened here.
Any ideas out there?
Thanks

[Paul Komski]

Have you checked that the power supply/adapter actually has an electrical output?

[DLeonR]

Have you checked that the power supply/adapter actually has an electrical output?

Yes I did, not only that; The battery is fully charged.

[Paul Komski]

Completely dead laptops have in my experience either had a motherboard failure or possibly a bad/loose connection somewhere. It can sometimes be worth reimoving the hard drive and optical drive and battery and see if there is any sign of life when you then attach a known good power supply and press the on/off button. And by dead I mean no fans spinning, no drives being accessed and no LEDs alight.

[DLeonR]

Completely dead laptops have in my experience either had a motherboard failure or possibly a bad/loose connection somewhere. It can sometimes be worth reimoving the hard drive and optical drive and battery and see if there is any sign of life when you then attach a known good power supply and press the on/off button. And by dead I mean no fans spinning, no drives being accessed and no LEDs alight.

I will try what you said later on, this is what you described as dead. No fan, lights, nothing.

[DLeonR]

I think I have opt for new motherboard for this laptop. I removed the HHD memory and opitcal drive and nothing. Where on this laptop will I find the correct model motherboard? I know on some laptops it is under the momory but not on this one. I need to purchase the correct boar. This is an Acer Aspire 7740-5691 laptop.

[FTT]

They are proprietary. You'll have to go through Acer or a specialty shop. I just found a mobo for $320. Heck you can buy a refurbished complete laptop for that price! :eek:

[Paul Komski]

You could try eBay for either a broken laptop available for parts or for a motherboard.

To be honest unless you know things inside out it is often better to bite the bullet and start anew. Swap the hard-drive and then sell the current laptop for parts/spares. The main value in a 2nd hand broken laptop is in the RAM and hard drive and display - and to some extent the various bits of plastic; keyboard, bevels, palmrests and so on.

[DLeonR]

You could try eBay for either a broken laptop available for parts or for a motherboard.

To be honest unless you know things inside out it is often better to bite the bullet and start anew. Swap the hard-drive and then sell the current laptop for parts/spares. The main value in a 2nd hand broken laptop is in the RAM and hard drive and display - and to some extent the various bits of plastic; keyboard, bevels, palmrests and so on.

Well, I think I will take your advice from both of you guys. I will not buy a new board. I will just scrap this laptop.
Thanks for the replies.

[DLeonR]

Does anyone knows what the "P" button on the acer aspire 7740-5691 is for? I don't have a manual on this laptop and I really don't want to buy one because I probably won't keep this computer.

Disregard this post. I found out what the "P" button is for.

[Mini-Me]

I have one of these today - HP530 laptop - totally dead.

PSU good, and tried another known good PSU on it, but it is totally dead - no signs of life at all, no LED's no fans no nothing.

I have come across this before once or twice, and I concur with the other posts here, it is generally a dead duck when that happens. If I had to guess, I would think the PSU part of the laptop motherboard has died, as there are no LED's even lighting up, which you often get when a laptop refuses to start.

The customer has elected to replace rather then spend any time trying to make it behave...

[Paul Komski]

When posting earlier I did leave out one other possible cause and that is that there is break/fault between the power adapter and its attachment inside. Just occasionally (and assuming one can lay one's hands on a good battery) a good battery can power things up and allow one to make such a diagnosis but you are still going to have to delve inside and mend a connection or replace some hardware therein.

[Mini-Me]

That's true - I have seen that too, but more often then not, it is not worth the time-factor to get to it, when you look at the price of a basic replacement these days.

I did make the attempt to fix one of those when it became a gift to me, but getting laptops to bits is something of a science in and of itself! :D

[DLeonR]

I have replaced main boards in a couple of laptops before, Toshiba and HP. I don't mind doing that, what I am terrible in doing, is soldering. I can't solder to save my life, but replacing a board in a laptop is not too bad, just require time and to be alone when doing it.
I might just take a stab at replacing the board in this Acer aspire 7740-5691 laptop. I just can't find a site with a reasonable price for one.

[Mini-Me]

Well, folks, I have come across something interesting with this laptop - glad I did not trash it.

It would seem that HP laptops are VERY sensitive about their input power voltage.

This particular one will not start on anything less then 19v, and anything over 20v...

But select 19v, and it fires up just fine.

The old PSU was supposed to be 19v, but was actually 17v, but I thought that would have been close enough to make it work - obviously not. :eek:

The "Known good" PSU I tried on it was an 18v unit, but it still would not start.
However, when I put it on my bench PSU, and selected 19.0v, the laptop fired up just fine, and ran perfectly fine.

I have used PSU's with lower output voltage to test laptops over the years with no problems at all - not that you would want to run them long-term like that, but for the purposes of testing, if you don't have the EXACT voltage PSU available...

Seems HP is pretty picky, but then, having discovered this, I can at least replace the PSU with a 19v one, and return it to the client. :)

[Paul Komski]

@ Mini-Me: presumably the battery was either completely flat or non-existent.

@ DLeonR: yes the mobos for that model seem not only few and far between but also very expensive. One other thing worth trying before trashing is to remove the board and then the cpu and anything else attached to it and spend 10 to 15 minutes with a hot-air gun going over all the solder points on the board; better results of reflowing the solder are achieved if you can also apply flux to them. Some people attemp such re-flowing by putting them in an oven but I have found this usually damages the board or little necessary bits of plastic or else parts de-solder themselves and fall off.

[Mini-Me]

@ Mini-Me: presumably the battery was either completely flat or non-existent.

Battery present.

Completely flat, due to failing PSU, but I would not have thought that would have made the machine so picky on input voltage.

Charging it up now...

[Paul Komski]

These things obviously have to operate within various tolerances. It is nonetheless a useful thing to consider for the future. I personally would think a 10% drop in input (19 to 17 V) as being significant - particularly since the potential power and current would be reduced by an even greater percentage; (since P=V^2/R and all that). Im open to correction but if my sums are correct a 10% fall or rise in voltage would lead to a 21% fall or rise in power and current - the resistance remaining constant of course.

[Mini-Me]

Agreed - assuming a 100% load current. Laptops current consumption is not constant, it varies up and down all the time, primarily due to CPU load.

Still...

[mjc]

Actually...I've seen enough HPs with that 'problem' to think that it may actually be a feature. I haven't been able to confirm it, anywhere, but I think that the power circuitry in an HP laptop has a +/- 10% 'range' and if it is out of that, it is shut off.

I've 'cured' more HP laptops than I care to count simply by replacing a 'good' power supply...one that showed it was 'working' by a light on it...most of the ones I replaced ended up with lower than spec voltage, though, when finally checked with a voltmeter.

[DLeonR]

@ Mini-Me: presumably the battery was either completely flat or non-existent.

@ DLeonR: yes the mobos for that model seem not only few and far between but also very expensive. One other thing worth trying before trashing is to remove the board and then the cpu and anything else attached to it and spend 10 to 15 minutes with a hot-air gun going over all the solder points on the board; better results of reflowing the solder are achieved if you can also apply flux to them. Some people attemp such re-flowing by putting them in an oven but I have found this usually damages the board or little necessary bits of plastic or else parts de-solder themselves and fall off.


I think I will try the hot-air gun on the mobo before chucking it. The motherboard for the laptop is very costly, it is amazing to me how they could sell the laptop so cheap with a board this expensive.

[Sylvander]

1. "it is amazing to me how they could sell the laptop so cheap with a board this expensive"
This reminds me of washing machines [WM's].

I was reading online, that [so their critics say] WM manufacturers deliberately inflate the cost of spares, so that users will NOT repair their machines [too expensive], but instead BUY A NEW MACHINE! :eek:

They want to create a culture of [cheap?] throw-away washing machines. :(
This hurts the WM repairers.

So some people [WM repairer background] got together, and asked a Swedish manufacturer to build a WM to their specification.
It would last about 20+ years.
The spare parts would be low cost.
The WM's would be easy to repair.
It would cost about 2 or 3 times what a cheap WM costs, but would end up low cost per year of service.
I almost bought one at £900 to £1000.

Once all the repairers have been put out of business...
Will the WM manufacturers then begin to increase their prices? ;)

[mjc]

I think I will try the hot-air gun on the mobo before chucking it. The motherboard for the laptop is very costly, it is amazing to me how they could sell the laptop so cheap with a board this expensive.


Actually with laptops and such, its a bit simpler.

They don't order/make many spares. Say they want to make 1 million of a certain model. They'll order maybe 1,025,000 motherboards, and end up with maybe 15,000 after the run. Out of that 'missing' 10,000 a good portion of the motherboards are still good, but other parts aren't...so they may end up being used for 'spares' too. But what you end up with is a very small number of spares...

It's the same for desktops that are prebuilt/use a custom motherboard.

Initially the cost of the board is very cheap, but since it was a single run item, no more can be made. Where as a 'motherboard' that was made to be used by anyone (standard/not custom run) is made in batches over several months...possibly even years, and for some boards, they can still be or are being made in small numbers, long after the initial runs.

[DLeonR]

It is true and I understand what you guys are saying, however, it does not apply to all laptops. I have purchased mobo for under $100; yet the board for this acer some sites are asking over $300. I know everyone want to make a billion dollars producing and selling their products but with that said, do they expect each time the computer breaks, you run out and spend another $700 bucks at the snap of your fingers. Before I go out and buy another laptop I will try to get a broken on off ebay with the motherboard working, if possible.

[mjc]

do they expect each time the computer breaks, you run out and spend another $700 bucks at the snap of your fingers. Before I go out and buy another laptop I will try to get a broken on off ebay with the motherboard working, if possible.

Actually, they do...they want you to buy the latest model, not repair the old broken one.

[Paul Komski]

I have purchased mobo for under $100; yet the board for this acer some sites are asking over $300.

I concur and I have bought many mobos as well as laptops for spares from eBay. There don't seem to be many hits for your model and those that there are seem over-expensive IMHO. Possibly that is why and that it is a model that didn't have high sales such that demand is much greater than supply.

[DLeonR]

[QUOTE=There don't seem to be many hits for your model and those that there are seem over-expensive IMHO.[/QUOTE]

This I agree with, I am between a rock and hard place. Perhaps just go for a new laptop.
Thanks to you guys. Good discussion!

[DLeonR]

Hi guys, I just thought of something else. Could it be the ac dc power plug in jack port for the acer aspire 7740-6591 that has gone bad? And if so, is there some way to test it before I go purchasing something I don't really need?

[Paul Komski]

Could it be the ac dc power plug in jack port for the acer aspire 7740-6591 that has gone bad?Indeed it could and it was the first question I asked in this thread. If there is no output then check that any plug fuse has not blown.

A multimeter is the easiest way to test it. Set for an appropriate DC range and touch the inside and outside of the jack; if zero or -ve then reverse the terminals to double check.

Using another power adapter (OEM or generic) is of course another way to go as long as the voltage and polarity are correct/appropriate.

[DLeonR]

Paul, I thought you asked about the power/adapter, I think the power plug in port is something else, that is attached to the board or perhaps I misunderstood. I tore the laptop down and got to the input plug where the power cord is attached and there is nothing loose or broken there and even if it was broken it would have required some soldering. So this is it for this main board on this laptop. Now I have to make up my mind on what I want to do. I really don't have the bucks for a new laptop and I can't find a board at a reasonable price. Every thing is see is over $350.00, that is half the price of a new laptop.