ASUS laptop won't charge

[Tim Downie]

I've got a friend's ASUS M5200 laptop that I've offered to look at.

It works fine when connected to it's power supply but dies instantly if the power is removed. There are only ever two lights on on the front of the laptop, one for the mains supply and one for the hard drive. The battery light never comes on. The power meter in Windows does identify the battery and shows it as having zero charge.

I've tried battery recalibration and a new battery has also been tried but neither helps, it still refuses to charge. More in hope than in expectation I've opened it up to have a look around but there's nothing obvious to see.

I'm guessing something has gone wrong with the internal charging circuitry.

Is there anything else I can do or have I come to the end of repair options (short of motherboard replacement)?

Tim

[Ken]

Remove the battery and see if you can measure the voltage present at the terminals the battery connects to while the charger PS is plugged in. If you see no voltage there, it is a safe bet that the internal components of the charging circuit are at fault. If there is voltage there, you might consider the possibility of the terminals not making proper contact with the battery.

[Tim Downie]

The contacts all look undamaged and are soldered securely to the motherboard. I'm not sure which contacts do the charging and what voltages to expect so I've not done that (yet).

Tim

[whit3rd]

It can be as simple as an open fuse (but it'll be a surface-mount soldered in fuse). It sounds like the charging circuitry isn't doing its job. Look for surfacemount MOSFETs that have failed if the fuse isn't the problem (or if the fuse, when replaced, blows again).

Basically, look at the power handling discrete components (fuse, sense resistor, PMOS switch transistors, etc.) near the battery connector.

[Tim Downie]

It can be as simple as an open fuse (but it'll be a surface-mount soldered in fuse). It sounds like the charging circuitry isn't doing its job. Look for surfacemount MOSFETs that have failed if the fuse isn't the problem (or if the fuse, when replaced, blows again).

This is where I have to admit to a considerable amount of ignorance. = What would a surface mounted fuse look like and would it be visibly = blown?

Tim (apologies for stupid quoting. Using my wife's Vista disabled laptop).

[Ken]

would a surface mounted fuse look like and would it be visibly blown?

No insult intended, but it sounds like this task might be beyond your abilities. First most laptops are not easy to disassemble. You could very well do more damage than good. If this computer is worth anything, you might try to find someone who has some skill repairing electronic items.

[Tabby]

- [e-mail]...

=A0What would a surface mounted fuse look like and would it be visibly blow= n?

It does sound like an electronic fault with the charging circutry if youve tried a new battery. And you're way short of the skills to diagnose and fix that.

Mains only laptops are pretty useful. If you had more skills I'd mention adding a basic slow charger circuit, bypassing the dead fast charger.

NT

[Tim Downie]

What would a surface mounted fuse look like and would it be visibly = blown?

I've taken a few apart. What's more, I've put most of them back = together again. ;-)

It's several years old and an "extra" laptop in the household. I doubt = it would be economically worth trying to get repaired unless the cost is = low enough.=20

I won't deny that it's probably beyond my skills. I was just hoping = there might be something obvious that was within my ability.

Tim

[Tabby]

eptember.org...

[e-mail]...

=A0What would a surface mounted fuse look like and would it be visibly blow= n?

it would be economically worth trying to get repaired unless the cost is l= ow enough.

it wont be remotely worth it

might be something obvious that was within my ability.

regrettably not

NT

[chrisj.doran]

-september.org...

[e-mail]...

=A0What would a surface mounted fuse look like and would it be visibly blo= wn?

ther again. ;-)

bt it would be economically worth trying to get repaired unless the cost is= low enough.

re might be something obvious that was within my ability.

The simplest and cheapest workaround for such problems is to buy on eBay a "spares or repairs" machine that uses the same battery and hope the charger circuitry still works. More elegantly, you can get standalone chargers for some batteries, but the cost will be about the same.

Chris

[Tabby]

al-september.org...

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e. =A0What would a surface mounted fuse look like and would it be visibly b= lown?

gether again. ;-)

oubt it would be economically worth trying to get repaired unless the cost = is low enough.

here might be something obvious that was within my ability.

I reckon a resistor from power pack out to battery + fitted inside the lappie would be simpler & cheaper. Charging would be very slow, but quite workable if its not used a lot on battery.

NT

[Brenda Ann]

I reckon a resistor from power pack out to battery + fitted inside the lappie would be simpler & cheaper. Charging would be very slow, but quite workable if its not used a lot on battery.

Even simpler would be to buy a rechargable battery of the same or close voltage as the AC supply and fit it with the proper connector to plug the battery into the AC charger slot. The battery could be recharged manually.