repairing Motherboard/MOSFET possible?

Hi all,

I got this Acer 6530G, that runs perfectly on battery power, and most of the time fails to run on main power supply.

With the battery removed and connected to mains, I normally get only a flashing power button. When leaving the laptop withou battery and *un*-connected to the mains for a while, I cn reconnect it to the mains, and start it up normally. However, it eventually dies (power outtage) after a few seconds or minutes.

I now took it apart, and found a spot that looks very suspicious - even more because it's close to where the battery connectors are located.

See the attached picture for yourself. Clear signs of excess heat, some connections are broken, the covering plastic is melted.

Now my question. Is something like this repairable? I have no clue, really, but half a year ago I didn't know you could bake motherboards, either, so I ask ...

When googling for "FDD 8878" (the label on the burned thing), I get this datasheet as hit, saying it is a 30V N-channel Powertrench MOSFET, which has been designed specifically to improve the overall efficiency of DC/DC converters using either synchronous or conventional switching PWM controllers. It has been optimized for low gate charge, low rDS(ON) and fast switching speed.

This also leads me to think that this burned thing is related to the problems I am seeing.

So, any luck to get this thing repaired without a machine worth a 1000$ bucks? I am more looking towards painting lines with my pencil to get connections back up ...

Thanks for any help!

Cheers

P.S.: I hope it is okay to start an new thread on this topic - it would be quite hidden in the old thread, and after all, it is no longer about flashing power buttons, but no about fixing MOSFETs. I hope its okay and I do not act wrong.

 

I can see a potentially blown inductor there too.

I think you would need to take it to a shop maybe with a replacement components and get them to do it if you have not done that sort of thing before.

 

Well, no, I haven't done this before and I am not planning to do so.

I wouldn't know of any shop around here performing such repairs, but allow me one last question - how much would this cost? I am happy with wild guesses as I have no idea. I think material would be worth 50 cent, but time is the bigger part ... 5€/$ ... 10€/$ ... 50€/$ ... 100€/$?

Cheers

 

There could possibly be other components that have failed... hard to say really without actually testing them and seeing a circuit.

It is possible to work on surface mount technology but if your not familiar with it.... hmmm. Also the FET will take a surprising amount of heat to remove if the tab is soldered... so the risk of more damage. Any connections would have to be repaired with wire... the current involved are far far to high for any conductive paint to carry. Motherboards are multlayer too... so there may be damaged connections within the PCB that you can not see.

Working with SMD. How to do it without specialised tools. - diyAudio

 

So, what you are saying is that it is beyond (economical) repair, or at least, beyond (economical) repair for a guy who has no clue what to do, nor has the proper tools, obviously, right?

Even if I could repair it for, lets say 30$ or 50$, I think I just put it on ebay as it is.

Cheers

 

I have sometimes found cheap 2nd hand motherboard replacements on ebay...

 

Realistically I think so.
For the FET to blow itself apart means a lot of current has passed through it. That means a low resistance path somewhere... failed flyback/efficiency diode a capacitor... it could be anything. There is a slim chance that if nothing obvious (other then the FET) looked burnt etc that it might just be a case of a failed FET and nothing else... but the odds aren't brilliant. In its favour... that it works on battery OK. Does it charge the battery OK ?

Without first hand looking at something like this its impossible to say. If you could come up with a circuit for that part of the board... it would all be much clearer.

 

The Ubuntu 10.10 tray icon and the LEDs on the laptop indicate that it is loading the battery, but it really doesn't get charged, I tested that.

As said, sometimes it starts on main power supply (and with battery removed!), but it eventually dies - sometimes after a few seconds, sometimes it takes a couple of minutes.

Guys, I think I just let it rest in piece - I will sell it as whole or in parts on ebay.

Thanks a lot for your help and insight!

Cheers

 

No problem... hope you get a good price for it