What was the reason for the new adapter? Did the old one fail due to a storm or power outage perhaps? If so, then perhaps the power components in the router have also been affected as well.
Have you verified that your new adapter is a 12VDC 1A (1000mA) output type?
If you have the correct adapter a solid amber power light indicates that it is doing a POST diagnostic (start up) test. If it is staying on this and not changing to a green light it means there either is a power problem or a hardware/software problem in the router itself,
Try restoring the router by pressing the factory settings button. Press for approximately 5 seconds to reset the router to the factory default settings.
If that doesn't work and you have the inclination to do so, with the router disconnected from everything, open it up and see if you can see any obvious problems inside. Look for burnt looking components etc. You can always take pictures of the inside and post them here Adding images to an existing question so that others can maybe spot what the problem is