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after having plugged the power-adapter with inverted supplies (19.2V +/- swapped) into the ASUS U5F notebook of my wife (you'll understand the severity of the problem), it has burnt a little bit and since then the USB (maybe the 5V supply) seems to not work correctly anymore (the rest seems to be ok).

To investigate the problem until now I found out the following:

  • the schematics of the mainboard are not available
  • the device seems similar to the Asus U5A (no schematics available either)
  • at least one component has burnt (as pictured below)
  • I'm unable to identify what this component is doing exactly, so I can't replace it
  • the components is of probably packaged using "SOT-223-4"
  • the marking code is 8C609 (I could read it before cleaning the section, now there is only "8C6" left)
  • I suppose it is a LDO-regulator, but I don't know the exact reference

Picture of the full motherboard

Picture of the section of the motherboard showing the section where the component is located

EDIT: The question now has a follow-up.

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  • \$\begingroup\$ Nothing to do with electronic design! Question will be closed. \$\endgroup\$
    – Leon Heller
    Commented Oct 20, 2011 at 9:58
  • \$\begingroup\$ That's too bad, because I found "similar" posts where people were asking for help to identify a component based on the markings. Would it help to remove some (non-important) information from my question? \$\endgroup\$
    – Patrick B.
    Commented Oct 20, 2011 at 10:03
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    \$\begingroup\$ Looks fine to me. Electronic design includes component identification and repair. \$\endgroup\$
    – Optimal Cynic
    Commented Oct 20, 2011 at 10:06
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    \$\begingroup\$ @Optimal I agree. I think Leon is out of order saying the question will be closed. As per the FAQ: Bad questions include "consumer electronics such as media players, cell phones or smart phones, except when designing these products or modifying their electronics for other uses" - this question is clearly about modifying said electronics, and so falls within our remit. \$\endgroup\$
    – Majenko
    Commented Oct 20, 2011 at 10:46
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    \$\begingroup\$ I too think this is a legitimate question. \$\endgroup\$
    – Olin Lathrop
    Commented Oct 20, 2011 at 12:43

2 Answers 2

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Your best bet is not to identify what part it is, but what function it had and replace that function. You will have to unsolder the part anyway. After that, you can start working out if and how it is connected to the USB port. If it is, you know what it does and can replace it with something else.

It is possible USB might work after you unsolder the part. Perhaps it is just some peripheral part, not the power supply to USB. In this case, the fried part might just be shorting USB power, which then shuts down.

If not, maybe (danger!) you can connect the USB 5V directly with Mainboard 5V from, say the harddisk plug. This would change how safe USB is (usually it is limited to a certain amperage), and you could fry the notebook with USB. But then again it is already toasted...

Usual warnings etc: dont burn down the house.

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It actually helps a little to know that these people in Russia were asking the same question in 2005. They mention 19V, which suggests that the charger voltage appears here, as you'd expect.

Based on all input I guesstimate that it may be a PNP transistor or P Channel transistor used as a high side switch for the adaptor power input.

Emitter or Source as shown. Similar for smaller device at left.
Knowing the label or functionality of the long thin device just above the 8C6xx would be interesting ( ...7C64? - but it looks more like a crystal than a memory).

The markings in red on the diagram are my guesstimates - not based on any sure knowledge. Knowing hat voltage is measured at the points marked "+19V" would be useful.

enter image description here

Candidates - examples only:

Bipolar

Infineon PNP Darlington BSP60 - 62. 45V+, 1A. Current too low for safety.

Better BDP954 PNP Infineon 45V+, 3A cont, 5A peak, SOT223.

MOSFET - MANY good candidates.

eg Zetex ZXMP3016GNTF6P02

6A+, 30V, SOT223-4

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  • \$\begingroup\$ The long thing just above is marked: 32C64 \$\endgroup\$
    – Patrick B.
    Commented Oct 20, 2011 at 13:44
  • \$\begingroup\$ One of my colleagues thinks the 32C64 is magnetic switch which allows/enabled optional/debug stuff. \$\endgroup\$
    – Patrick B.
    Commented Oct 20, 2011 at 17:00
  • \$\begingroup\$ Another question which raises is what would be the use of such a circuit knowing that the lower edge of the 8c609 would also provide 19V to the component on the left? Which bother putting it in place and not connecting it directly? I will check more later and provide better pictures of the surroundings. \$\endgroup\$
    – Patrick B.
    Commented Oct 20, 2011 at 17:03
  • \$\begingroup\$ @PatrickB. The long thin component looks very much like a 32768 Hz crystal. There are 4 terminals and often the two on one end are the active ones and the other two are just mechanical. - google.com/search?q=smd+32768+crystal&tbm=isch \$\endgroup\$
    – KalleMP
    Commented Jun 28, 2018 at 7:28

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