Replacing Dell Laptop Power Cord 19.5V vs. 19.0V

Discussion in 'Computing and Networks' started by elec_mech, Aug 28, 2011.

  1. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008
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    Hi All,

    History:
    A coworker has a bum laptop power cord. When I first looked at it, there was no voltage coming out of the coaxial connector, but the green LED on the power brick was on. I noticed some electrical tape around the output cable (DC side) and noticed something had pierced it at one time. I did a continuity check, but no short between the tip and outer conductor. I tried popping the brick apart to look at the inside and make sure the problem was with the cable and not the supply, but couldn't open it.

    I powered it up and now the green LED is off and I can hear a high pitched whine coming from the brick. This is rated for 19.5VDC output.

    Question:
    My question is - unless someone has a surefire way of fixing the brick - can I use another Dell laptop power supply with a slightly lower output voltage? The bad one that I need to replace is rated at 19.5VDC and something like 3.84A. The spare I have is rated at 19.0VDC and something like 4.34A, so I'm good current-wise. My question is how sensitive are laptops? Will a 0.5VDC less make a difference?

    Thank you in advance.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    The voltage should be ok. Are you sure the power cord has only 2 contacts?

    I have/had various DELLs and the DC plug has an outer ring, an inner ring and a middle pin. I don't know why there are three contacts, but make sure you have the right spare power adapter with the right polarity etc. before you plug it in.
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    Regarding the voltage you should be OK. However it could be that your laptop will not charge the battery due to wrong kind of power supply. But anyway it will do no harm to test it
     
  4. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008
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    Thank you guys! The plug appears to be a standard two conductor with an outer barrel and a center pin, but I will double-check before moving forward. I'm going to have to swap the plugs anyways, so I'll check to see if the cable has two or three wires.

    I was wondering about charging the battery too. I'll give it shot and see what happens. As long as I'm not going to damage the laptop, I'm happy to move forward and give it a shot. Thanks again!
     
  5. radiohead

    Active Member

    May 28, 2009
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    You could probably find a replacement brick at a flea market for around $10 or so.
     
  6. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    The center pin I was talking about seems to be a communication wire, necessary to charge the battery, the laptop recognizes what kind of power supply is connected. The outer sleeve seems to be negative, the inner ring positive. That's what I read HERE.

    These are the DELL connectors I know, and an IT-guy from my fathers company killed once the mainboard using a non-DELL power supply, applying voltage to the center pin. If you don't have this type of connector, even better. ;)
     
  7. JDT

    Well-Known Member

    Feb 12, 2009
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    In my experience Dell power bricks have an extra connection. Outer ring, inner ring and a pin. The motherboard communicates using this and if it's not a genuine Dell part then it won't charge the battery!
     
  8. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008
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    Update:

    Thank you folks! I checked the power supply and you were right, there are three conductors, one on the outer barrel, one on the inner, and the center pin. Looks like the comm wire is a little over 12VDC.

    There was a damage to the output wire, so I cut it and rewired, checked the output and everything looked good. Plugged it in and nada. Had an identical good Dell supply and tried it in case I messed something up with the original, still no power to the laptop.

    I also added solder to the power connection on the motherboard just in case something came loose. Still no joy.

    Do you think the laptop is toast? Do they build fuses into the laptops that can be checked? Anything else I should look at? I already took it fully apart once, so this isn't a problem to do again. Thanks in advance!
     
  9. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Open the laptop, plug the power plug in and verify if you have voltage on the mainboard.
    If you have it I guess it's time to look for a schematic, unless you see something burnt.

    What's the laptop model?
     
  10. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008
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    Thank you praondevou. I'll give that a shot - I was a little leary of powering the board with everything else disconnected, but logically speaking, that shouldn't hurt anything. I'll have to get back to you on the model - it's at home and I'm not. Thanks!
     
  11. t06afre

    AAC Fanatic!

    May 11, 2009
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    Try to take out the battery for a while. Plugg in the power supply and see if you may wake it up then
     
  12. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008
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    I will give that a shot. I'm about to head out of town for a week, so it'll be a little while before I can look at this again.

    The model is a Dell Inspiron 1150.

    Thanks guys!
     
  13. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Google this schematic: ibiza la-1684. See if it's the right one. Page 4 gives you an overview about the power distributions.
     
  14. elec_mech

    Thread Starter Senior Member

    Nov 12, 2008
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    praondevou,

    Awesome! I'll check it out upon my return. Thank you!
     
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