Laptop Power supply not working after 3 seconds

[romullma]

Hi folks.

I hope you can help me with this problem, but first of all I have to say that I'm just a hobbyist of electronic (and do not practice too much).

I have a problem with my laptop AC adapter, it's not working any more, there is no output voltage.

I've observed that I get the 19 output voltage only during 2 - 3 seconds after to have discharged the big electrolytic capacitor. After that, it dies again.

Please, do you know what can I do?, what do I need to test? How?

I can try measuring voltages (eg: I get more than 600 V at the high voltage section), but I have no idea what are the normal values.


Any help would be appreciated.
Thanks a lot.
Marco R.

[torbjorn]

Normally you should not have more than slightly above 300 V anywhere on the primary side of the adapter.

Which make is it? In some cases, laptop chargers use a control signal from the laptop (third wire in the cable) and switches off unless the laptop explicitly demands power.

Most problems with such units are due to bad electrolytic capacitors (look for bulged ends or signs of leakage) or heat damage. In particular, it is common that the glue used to fix heavy components begins to carbonize and then causes leakage currents. In such cases, the cure is to scrape and wash away unnecessary glue residue from critical circuitry. Remember that the glue might have creeped under electrolytic capacitors and other big components, so those might have to be removed to permit cleaning.