hey,

After a coffee disastrosa i'm now stuck with a broken Acer Aspire 7740G laptop.
The charge indicator light is not showing and when plugging in the adapter i get a
ticking noise (clock like) which stops when removing the processor.

I don't have much experience with motherboard repair (other than replacing some DC jacks) so i will
leave the desoldering and soldering (if any ) to a specialised shop with the correct tools.
But i like to take this opportunity to troubleshoot the problem myself. I don't have any electronic
troubleshooting skills whatsoever but i'm decided to find the problem, even if it will take years .. .
This is for reasons of pure interest in the subject and no direct need for the laptop.

I'd like to get into the world of motherboard repair, but to find my way through all the information is just not easy
So i'd like to ask if anyone could point me in some directions in which to go to learn and figure out these problems..
or has some information on what this specific case could be.

any help is appreciated!
E.

 

hey,

After a coffee disastrosa i'm now stuck with a broken Acer Aspire 7740G laptop.
The charge indicator light is not showing and when plugging in the adapter i get a
ticking noise (clock like) which stops when removing the processor.

I don't have much experience with motherboard repair (other than replacing some DC jacks) so i will
leave the desoldering and soldering (if any ) to a specialised shop with the correct tools.
But i like to take this opportunity to troubleshoot the problem myself. I don't have any electronic
troubleshooting skills whatsoever but i'm decided to find the problem, even if it will take years .. .
This is for reasons of pure interest in the subject and no direct need for the laptop.

I'd like to get into the world of motherboard repair, but to find my way through all the information is just not easy
So i'd like to ask if anyone could point me in some directions in which to go to learn and figure out these problems..
or has some information on what this specific case could be.

any help is appreciated!
E.

The batteries are likely dead and your power supply is twitching because they cannot find a reasonable load to charge (batteries are bad).

If you replace battery and still bad, replace power supply.

If it still doesn't work, go buy one of these...

http://www.ebay.com/itm/ACER-Aspire-7740-7740G-Intel-Motherboard-/121965940658

 

The batteries are likely dead and your power supply is twitching because they cannot find a reasonable load to charge (batteries are bad).

If you replace battery and still bad, replace power supply.

If it still doesn't work, go buy one of these...

http://www.ebay.com/itm/ACER-Aspire-7740-7740G-Intel-Motherboard-/121965940658

If I understand correctly, you spilled coffee into the computer. If so, then, before replacing anything you need to remove the batteries and thoroughly clean everything with distilled water and alcohol. The hard drive may be a problem to clean without damaging it. Follow this with a warm air dry until there is no trace of moisture anywhere.

Others here can tell you better how to do the cleaning than I can...

 

Thank you, the area that had liquid on it was very small and was dried and cleaned with alcochol immediately after the spill.
The battery was broken before, so that i could only use my laptop with adaptor.. but then i still had a charging light.. now the twitching sound does not come from the power supply but from somewhere on the board.

So still, my best option is to buy a new battery? also the power adapter works on another laptop so nothing wrong with that

 

Liquid has a bad habit of being sucked up by narrow spaces, like underneath ICs, and it is very difficult to get it out from under there. A very thorough rinse (don't be mean with the quantity) with distilled or demineralised water will also go into tight spaces and wash out any coffee remains. Then make very sure it is thoroughly dry before applying any power to it. Remember the water has to evaporate from those tight spaces too.

I tipped a glass of orange squash into my laptop. That's much worse than coffee. It didn't like it. I took the top off and as we have very soft water here so I took it to the outside tap and ran water all over it from all directions. Then I shook out all the excess water I could and left it for a week in a nice warm place with some air flow and it's back working again. As a side benefit it also cleaned out all the muck from the fan and heatsink.

The hard drive may be a problem to clean without damaging it.

The actual drive itself is sealed so the water shouldn't get in there and the electronics board won't mind the water so i think the HDD will be fine too. Mine certainly didn't mind. More care should be taken with the CD/DVD drive though as the head optics are exposed and delicate so remove that drive before washing.

 

Thank you, the area that had liquid on it was very small and was dried and cleaned with alcochol immediately after the spill.
The battery was broken before, so that i could only use my laptop with adaptor.. but then i still had a charging light.. now the twitching sound does not come from the power supply but from somewhere on the board.

So still, my best option is to buy a new battery? also the power adapter works on another laptop so nothing wrong with that

Try removing th battery and then plug in the adapter to turn on the lappie. If it works, it is the battery. If it still clicks, then the short is on the board. The fact that you can hear something means it's mechanical. Few mechanical things are the hard disk turning on then immediately shutting down (which would happen if the intelligent motherboard finds an over current issue anywhere (or the power supply feels like it is supplying too much current).

The other mechanical item is possibly a circuit protection relay that triggers when an issue is detected.

 

If it still clicks, then the short is on the board. The fact that you can hear something means it's mechanical.

Switch mode supplies can make clicking noises when they detect a fault and are repeatedly powering up then shutting down again. I'm not sure what actually generates the noise, possibly the transformer/inductor.

I have seen a high current supply doing this and you could see the wires twitching and making the noise. Presumably this was caused by the magnetic field generated by the high current in the wires.

 

Switch mode supplies can make clicking noises when they detect a fault and are repeatedly powering up then shutting down again. I'm not sure what actually generates the noise, possibly the transformer/inductor.

I have seen a high current supply doing this and you could see the wires twitching and making the noise. Presumably this was caused by the magnetic field generated by the high current in the wires.

https://en.m.wikipedia.org/wiki/Magnetostriction

Current causes more of a buzz than a click. Maybe a buzz sounds like a click if it happens fast enough. On the other hand, I'm not sure how much of a buzz at laptop currents.

 

Try removing th battery and then plug in the adapter to turn on the lappie. If it works, it is the battery. If it still clicks, then the short is on the board. The fact that you can hear something means it's mechanical. Few mechanical things are the hard disk turning on then immediately shutting down (which would happen if the intelligent motherboard finds an over current issue anywhere (or the power supply feels like it is supplying too much current).

The other mechanical item is possibly a circuit protection relay that triggers when an issue is detected.

Thanks. I checked by removing the battery and HDD and plugging in the adapter, but the clicking is still there. So the sound must come from the mobo. I cannot exactly pinpoint the component that is making the clicking sound but it's a very consistent tick (about 80 bpm).

Where would if find these circuit protection relays on the board? And if it were those signalling an error how would i troubleshoot from there on?

 

A good rinse followed by a good dry is a lot easier than fault finding.

 

A good rinse followed by a good dry is a lot easier than fault finding.

I did this with isopropyl alcochol, nothing changed..

i'm gonna start looking for schematics of the board and start testing components individually. If anyone knows where to get these that would be a great help.. as so far i don't seem to find them (free..) but i'll keep looking. If no result i will buy them and give an update here.

Thank you for the efforts so far!

 

I have saved many, many cell phones by simply removing the battery and putting them under a hair dryer for about a half hour.

I remember once when I was on a bicycle tour of the Great Allegheny Passage bicycle trail. We pulled into a campsite that had all the comforts of home, including showers. Run by a gorgeous blond woman with an equally gorgeous blond daughter. So close in age they could have been sisters.

Anyway I got the idea to get straight into the shower with my bicycle shorts and jersey figuring I would safe time in rinsing my bike clothes. Well I forgot about my cell phone!

I then had to go into the office. (Note I have male pattern baldness and also keep my hair very short especially when on tour). Both mother and daughter were on duty in the office. I said "this is going to sound like a really strange question but can I borrow a hair dryer"? They complied and I was able to save my cell phone and use for the rest of the tour!


Your problem is going to be sugar. Was there sugar in your coffee?

 

I

i'm gonna start looking for schematics of the board and start testing components individually. If anyone knows where to get these that would be a great help.. as so far i don't seem to find them (free..) but i'll keep looking. If no result i will buy them and give an update here.

Unless it large cap or something doubtful if you will be able to fix it even if you can locate the component. I would replace the system board or just bite the bullet and buy a new (or refurbished ) lap top.

But I would still giver the hair dryer idea a try. I once saved a phone I found on the road during one of my rides (many of my hand tools were found that way). I got it working and got the phone number of the owner. I called it and the guy couldn't believe it because the phone had been on the road for weeks through several rainfalls.

 

I have saved many, many cell phones by simply removing the battery and putting them under a hair dryer for about a half hour.

Thanks for the tip, but I believe the battery isn't the source of the problem. As by leaving it out ,using only the power adapter the laptop should be able to bypass the battery i believe (i've been able to use my laptop without the battery in before). But the hair dryer idea is a must, you're right. I did try it for the battery and the whole board ,but this time without succes.

ps. no sugar, just black.

Unless it large cap or something doubtful if you will be able to fix it even if you can locate the component. I would replace the system board or just bite the bullet and buy a new (or refurbished ) lap top.

I just like to figure it out first, just out of pure interest. But i believe you're right in that I will not be able the fix it myself

 

Thanks for the tip, but I believe the battery isn't the source of the problem. As by leaving it out ,using only the power adapter the laptop should be able to bypass the battery i believe (i've been able to use my laptop without the battery in before). But the hair dryer idea is a must, you're right. I did try it for the battery and the whole board ,but this time without succes.

If that doesn't work, I would try alcohol rinse again. If that does not work you could go to distilled water it's cheap. When I worked at TI I seem to remember an acetone bath we would soak PCBs in. The had mostly all discrete components. They were boards for the Harpoon missile seeker. So both fragile and very expensive. I think the seeker alone cost $125K back in the 80s. It is rumored that the engineer that designed the AFC board went insane after designing the board because it was so densely packed with components.

I would try a couple of rinses and drying. In stages of course What is it going to hurt?

Another idea to to pack in in slica gel desiccant for a couple of days. If you can't locate enough of those then buy a couple of large packages of rice, pour them into a box or tray and cover the system board.