HP Laptop power adapter beeping

Hi everyone,

I have an HP HDX18 1080EL laptop (the one larger than me :P ), with an 18.5V 6.5A power adapter.
Organized a party last night, using the laptop as an source, worked fine, but now I'm back home and when inserting the power adapter in the outlet, it started beeping with a ~2KHz sound every half a second. No output voltage or charging.

I think it may be a short-circuit on the wire, but not sure - has anyone else experienced this issue?

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  1. Problem solved.

    There was indeed a short-circuit at the cable in the first 2 cm from the power adapter end.

    I found out by de-soldering the ground wire from the PCB and measuring with an ohm-meter to figure out if the short was on the board or in the cable. Finding that short circuit was in the cable, I measured the conductor reflection distance (impulse method using oscilloscope), and found that the fault was at the power adapter end.

    The cable has 3 wires, in a double-mantle coaxial configuration (core = ID, mantle 1 = VCC, mantle 2 = GND).

    I dismantled the first centimetres of the cable and seems that the design of this cable is quite poor, as when applying longitudinal force, the mantle between the VCC and GND conductors cuts out, leaving a 0.5 cm non-isolated area (= short-circuit).

    So I separated the GND wire in a different isolation, measured again to check for shorts, and re-soldered it to the board.

    When plugged in the 230V AC adapter, no beeps, and the voltage was ok, so I plugged in the laptop - voilà - recharging without problems.

    Conclusions: I know that the cable is not meant to sustain such forces (as opposed to the finger-thick audio cables I'm used to), but the design could have been a bit better to prevent this from happening. Also, a modular cable would solve the issue and not require engineering skills to repair.

    Cheers, and be careful with the power adapter.
  2. Showoff :) Not everyone who has an oscilloscope knows how to measure the conductor reflection distance.
  3. I 've experienced that too, i need my laptop for work and i can't wait for 2 week to receive another adaptor from HP so i fix it my self :D
    there a short-circuit at the wire and i have to cut and reconnect these 3 wire.
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