Saturday, July 24, 2010

Acer 5515 Works off Battery, Charges, but will not run off AC

This unit arrived working from a charged battery, but will not power on from AC. 
My first thought was bad leg on the DC Jack, Easy job! Finally


Upon opening the case and removing the keyboard I saw the beginning of the failure. Burnt MOSFET under the keyboard directly behind the battery connector.


So took the rest of the panels off to see how bad it was. Out of a scale of 1-10 with 10 being the most difficult I rate this as a 7.5 because it was more annoying than difficult. The copper under the MOSFET was actually welded to the legs of the FET, heating solder would not break the weld.














Click to see larger image
The visual shows almost the worse case scenario for a shorted MOSFET. Burnt and totally unreadable numbers.  Seeing the circuit I surmised that it was an identical pair of chips but I had to verify against another motherboard to be sure.  Also there was a scorch mark under the keyboard, but it didn't affect the keyboard or any keys.
















Removing part and making a copper bridge for the legs of the replacement MOSFET was a little challenge getting it right and isolating it
from the center plane of the motherboard if copper was exposed. In this case a small piece of mylar tape will be placed under the copper retrofit.














Sizing and fitting the copper 'jig'. This was made from thin copper foil and cut with exacto knife and placement test made to see if the Gate lines were shorting or any other pads before making it permanent and not being able to remove it. 














Replacing the MOSFETs and soldering broken traces. In this case the  GATE line was blown away on both FETs so I got 2 small segments of wire and made the necessary bridges to the GATEs.




















Soldering the Gate line and cleaning up.  Now if you wanted to be fancy you can cover the solder and copper with some green fingernail polish, or clear polish and use a green marker over the polish after it dries. Then the repair will appear less noticeable.  


Notice the line at marking PR152 which was not so clear as being broken because it goes under the chip.




After doing all this I tested with the battery in place and with AC before closing up the laptop. No worse feeling than to have to redo after assembling things thinking you are done. ARRRGH It happened to me and so I started testing before closing.


As always you can click an image to see a larger version of it, and use the BACK button/Arrow to return to the page. Conversely- Shift and Click works best and automatically loads image in new browser.

4 comments:

  1. Wow, that was really toasted! Nice job. It's a little hard to see the detail (e.g., at PR152) because the pictures are a bit blurry. What do you use to take your pictures?

    Thanks for your very interesting articles. Very happy to see them coming on a regular basis like this.

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  2. Larry: see the previous picture for sharper view. For these closeup shots I have to use a Canon 7mpx digital camera on a tripod and hand held magnifier in front of the lens. Helping Hands does not help and my hand may be the one that is blurring the magnifier.

    Sometimes stopping to get the right shot is time consuming, but I make an effort.

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  3. Thanks. I appreciate the problem (and your time and efforts) and have been contemplating purchasing an achromat close-up lens for such shots myself. (http://cgi.ebay.ca/Marumi-55mm-55-DHG-Macro-5-200-Achromat-Close-up-Lens-/360279527625?cmd=ViewItem&pt=Camera_Filters&hash=item53e25550c9). Not sure I'd use it enough to justify the cost but I haven't found any other satisfactory means of taking sharp macro shots using my digital camera. It's those close-up lenses that introduce the blur, I believe, unless they are achromats.

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  4. good articles! at last someone who really knows electronics rather than a replace-this-module kind of guy.

    I have a broken Acer Aspire 3680, it does not start when the power button is pressed, although the charging LED indicator lights up when power adapter is plugged-in. This is the reason i stumbled into your blog and found your Acer Aspire 3680 article.

    I tried looking for the same capacitors and mosfet you pointed out, I could only do a visual check and a voltage check. i checked the 3 capacitors you pointed out and all were registering ~19V, so i guess they were ok.

    i could not test the mosfet though as i do not know how, maybe you could demo in one of your articles how to.(or i just have not read them yet) :)

    i'm hesitant to bring my laptop to a service technician since here in the Philippines they're somewhat like a shoot-or-miss, replace-this-module kind of technicians.

    i have a basic knowledge of electronics and Physics, and could fix simple issues, but when it comes to tracing the issue from a PCB, I'm dumbstruck!

    Anyway thanks for the interesting posts and keep it up!

    Erik,
    from the Philippines

    ReplyDelete

I cannot repair laptops for you via the internet, I can only answer questions related to posts. This is because I have not had experience on every motherboard that is out there. Bear with me.

If you do need it repaired. Contact me for quote (US/CDN Only)

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