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If I press POWER all the lights are ON only for 2 secs and then OFF again

I don't know the cause, but suddenly my laptop died and now when I press POWER all the lights are ON only for 2 secs and then OFF again.

I opened the case and identified a burned voltage regulator near the battery charging socket. I replaced it with an equivalent spare part, but the fault is not removed. I measured all the motherboard test poits, from the adaptor socket down to the battery and it seems it is working OK, especially that when the voltage regulator was burned it was not charging the battery.

Now with the battery in its place, the battery is charging, but the laptop is not starting.

Any helpful ideas?

Thank you in advance !

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  • 4 more comments 
  • Julian Von Braun
    Julian Von Braun Oct 29, 2008

    I forgot to mention - the laptop is an ASUS A7D

  • jparjun Oct 29, 2008

    Ihave the same problem as mentioned above. My warrenty just got expired 1month back.

  • Julian Von Braun
    Julian Von Braun Oct 29, 2008

    All the attached items are removed because the board is under repair (only processor left). Now I extracted the soldered component again (3 legs on one side + ground leg on the other side, aprox 2mm size in length, black colour, similar to a small transistor) and I saw that actually the battery is charged event without it. The main problem now, that is confusing me, is related to where I can find some info about the burned component. The marking is 8C546, no manufacturer logo, nothing else than the code.

    If somebody knows something about this item or an equivalent value for it or can figure out who is the producer, it will be very useful for me.

    Thank you again for the answer, but it would be nice to be so simple :)

  • Julian Von Braun
    Julian Von Braun Oct 29, 2008

    The item I am looking for is an SMD component, SOT-223 / SOT-89 type

  • Julian Von Braun
    Julian Von Braun Oct 29, 2008

    But can this 8C546 (Motorola) or F28C546 (Fairchild) be the cause of not starting the laptop? Or there is another item that is not working as well?


  • Julian Von Braun
    Julian Von Braun Oct 29, 2008

    Nothing is pluged in, except the main processor, memory module, battery and AC adapter :)

    The problem as I said is mainly with this component, because I dont't know exactly its function and I can't find its datasheet. I tried at Motorola and Fairchild but unfortunately no result. I also made an alternative research, considerind different spelling line 8C-546 or 8C 546 but after looking in all the results nothing interesting occured.

    I will assume it is an 3 terminal positive voltage regulator and I will try to use an equivalent part and make some measurements on the path between AC adaptor socket and battery socket.

    Also I was thinking that maybe the switch ON/OFF controller that interprets the digital 0 or 1 signal and orders the power on function in you press ON, can be faulty in connexion with an power gate DC-DC but I am not sure.

    First, before going further I must identify this component :)



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I would remove all attached items. memories, hard drive, battery.
unlpug the AC. push and hold the pwer button for 20 sec. (discharge the PC).
plug in the AC and turm it on. (BIOS) only. if that is good, then install other devices.

Posted on Oct 29, 2008

  • 1 more comment 
  • Frank
    Frank Oct 29, 2008

    8C546 is porduced by Motorola or equiv.F28C546 by fairchild. this should be an IC chip. I don't remember, its being so long I look at any of the IC. This should be gated IC, in otherword, it is a regulator with a votlage trigger gate.

  • Frank
    Frank Oct 29, 2008

    that might be the problem, I can't really say that is the problem. In general I have see the laptop to tell you what is wrong with unit.

    there are probably few other items that need to be replaced. you can only go one step at a time, and fix one thing at a time. and on, and on....

    I would pull the hard drive out of the laptop and test the unit that way. It is safer, not to kill the hard drive in the porcess.

  • Frank
    Frank Oct 30, 2008

    unfortunately I can get the data sheet. Data sheet is only available to ckt designer. I haven't being in that position over 10 years.

    you can ask any friends who working in electronic or ckt design.


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