Our Dell XPS M1710 will not power up using the AC adapter, it will power up with the internal battery and the AC adapter will charge the battery. We changed the mother board with the thought that the connector could be the problem. It still doesn't power with the AC cord. The error message is" 90 watt AC adapter is detected and the system requires 130 watts" There is no 130 watt AC adapter available. The problem started when the AC adapter went Kaput and we replaced it with another from Dell! We also get the same error message when we plug in the car adapter, which worked fine prior to the AC adapter failure.
If you replaced the motherboard and the AC adapter will still not work, it is an issue with the adapter. I'd get in touch with Dell support to see what they have to say, as there may be another adapter out there that will work. Plus, it may be a common issue with the M1710, which if it is, they would know about it.