Hi folks
I have a lab for repairing laptops and i came up to a common problem with these series D600, D500 when used with a fake cheap AC adapter caused the laptop to stop working with AC and now it works only with charged battery even if i'm connecting it with a brand new original dell AC adapter.

I assume it damaged something in the DC convertion on the MoBo, maybe a dead voltage regulator / diode or a bad capacitor but i'm not able to track it down

any help or point for direction will be much appriciated.....

I don't know if the Dell D600 has a separate DC board or the DC regulator is part of the motherboard. Maybe the DC jack is broken...

I had this with dell d-series and third party car power plugs. in most of the times it just helped to hardware reset the laptop. remove any installed device, memory, battery, harddisk, dvd drive, pcmcia, anyting you can remove. hold the power on button down for like 30 seconds. then plug in the power jack and see if you can start the laptop (still with nothing installed). if it does, unplug the power jack and put back in everything you took out and try again.

inverter8, look at pwm charger in these laptops and try to replace it. dell(means compal or quanta) mb's usually designed using 2nd level smbus chargers, so, part of AC's middle pin schematics comes to this pwm-controller too. chargers may be: max 8731 or something else, look at datasheets for these chips. usually, laptop vendors are don't change typical circuits provided in datasheets from manufacturers(maxim,ti,isl,sc).