Laptop part identification

Discussion in 'General Electronics Chat' started by Nk1, Mar 22, 2015.

  1. Nk1

    Thread Starter New Member

    May 27, 2013
    7
    0
    Hi this is a medion laptop that runs of battery power but will not charge a battery. On the photo charger socket bottom and just above in middle of pic there is a small oblong peace on charging circuit. I think this has failed can some one tell me what it is and can i replace it thanks.
     
  2. paulktreg

    Distinguished Member

    Jun 2, 2008
    611
    120
    PF501? Possibly a fuse as it's directly in line with the power input as far as I can tell. What does it read on ohms?

    The photo could be better?
     
  3. Nk1

    Thread Starter New Member

    May 27, 2013
    7
    0
    I just tested voltage on one side i had 19 volts the other side 0. On a different board i had 19 volts both sides i looks possible to replace but don't no what it is thanks for reply
     
  4. Roderick Young

    Member

    Feb 22, 2015
    408
    168
  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    If it's open then there is probably a reason for that. I'd measure the resistance from the output (that reads 0) to GND. You might have short somewhere

    EDIT: well just saw that roderick said the same thing :)
     
    Roderick Young likes this.
  6. Nk1

    Thread Starter New Member

    May 27, 2013
    7
    0
    Ok thanks for the replies ill have a look tomorrow
     
  7. Nk1

    Thread Starter New Member

    May 27, 2013
    7
    0
    Ok finally got round to checking this it looks like the thing to the right of the poly fuse could be the problem. A small round thing that bridges across from positive to negative just above charger scoket.
    So does anyone no what this is and what it does. image.jpg
     
  8. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    Looks like it has a cathode mark on it and a diode silk screened under it...

    BR
    Dennis
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,798
    1,103
    Agreed; looks like a diode. Is the mark under your arrow 'PD501'? A meter check should show higher resistance one way than the other. The 'D' in PD502 suggests that's a diode too.
     
  10. Nk1

    Thread Starter New Member

    May 27, 2013
    7
    0
    Yes its PD501 could this fail and cause a short. And why does it bridge the charging circuit looks like it goes across positive and negative from charger socket.
     
  11. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    It may be a reverse voltage protection diode. That would protect the mother board from an external source having the wrong polarity. If one was connected, it may have resulted in a shorted diode. I did that once connecting a rechargeable battery to my bench top power supply. The reverse polarity diode protected the power supply from the battery current by conducting, then shorting.
     
    Roderick Young likes this.
  12. Nk1

    Thread Starter New Member

    May 27, 2013
    7
    0
    Thanks for replies after testing on meter there is no resistance so it's blown. Does any one no best place to get a replacement here in the uk and what spec I need
     
  13. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    PD502 looks like a regulator to me.

    Looking at the Pletter501 and Pletter502 etc I would think that these are simply taken from bins marked with this scheme without regard to component type for assembly by unskilled labour.
    That is they take whatever they find in bin PA501 and put it in location PA501 on the board etc.
    There will probably be other letters identifying other parts of the board.

    PD501 will be a 5amp 50 or 100 volt diode if the diode idea is correct.
    Two things to check

    dl324 pointed to a silk screen character. Is that a diode and is that the correct way round for reverse protection?
     
  14. Roderick Young

    Member

    Feb 22, 2015
    408
    168
    If it was, indeed a diode, and connected the non-conducting way across the output, then maybe you could simply remove it, and see if the assembly came back to life? Afterwards, you could then decide what kind of protection to put in.
     
  15. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Why would it be connected the non conducting way?

    I think the idea was a series connected diode to protect against reverse connection of the power supply.

    A parallel connected diode could have been connected as sacrificial protection against overvoltage, but I doubt it.
    In any event the component is non conducting now and if it was connected so it was non conducting in normal service how could removing it make any difference?
     
  16. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    The OP said it bridges between the Pos and Neg just above the charger socket (re... post #7), therefore it would protect against a reverse polarity input. Not too uncommon form of protection.

    Also, the OP said it shows no resistance. Clarification is needed as to the meaning of "no resistance"? Does that mean short or open to him?
     
  17. paulktreg

    Distinguished Member

    Jun 2, 2008
    611
    120
    I'm with studiot.

    Why put a diode across the supply that will probably be destroyed by reverse connection of the DC supply? Does it not make sense to put a suitable diode in series with the positive supply. it protects against reverse connection and doesn't get damaged in the process?
     
  18. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    Hi Paulktreg,
    If I was protecting against an incorrect power supply being used, I'd add a few more diodes and make the input independent of polarity. But that would add extra cost and it adds up if you plan to ship a lot of units...
     
  19. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    Besides all of the above, a series diode would prevent needed repair. Design engineers, now days, seem to go out of their way to insure DIY repair is very difficult, if not impossible. Automobile repair often requires "special" tools to even gain access to the problem Or one bolt will be mounted behind some other part requiring major disassembly just to make an otherwise minor repair. I think they must teach this in school now.
     
  20. Gdrumm

    Distinguished Member

    Aug 29, 2008
    684
    36
    What model # is it, and does it require a 150 watt 4 pin ac adapter?

    Apparently these are fairly high end laptops, so I would expect good design.

    Just curious...
     
Loading...