You plugged in a 18V Lionchief DC adapter into a Legacy base????!!! Of course a DC Lionchief adapter would not work.
That's good way to burn up a very expensive and hard to replace base.
Even your 12V AC adapter is not the "correct" one but no wonder you had problems.
Get the right adapter before you cause even more problems.
I know my answer might come off as harsh but clearly you do not understand the gravity of the situation. I'm trying to save you money and prevent a costly mistake.
Do you have a Legacy 990 base- just making sure, VS a CAB1L blue base?
The correct Legacy base adapter is only 8V 2 Amp AC https://www.lionelsupport.com/...CY-BASE-8-VOLT-2-AMP
Yes, click on the link above and order one (they are in stock as of this moment) or find out if you have one. Again, given Legacy bases are out of production, given there is a finite number of repairs Lionel can do before warranty support is gone possibly forever- you really cannot afford to risk damaging a legacy base with the wrong power adapter.
8 Volt 2 Amp AC 
https://www.lionelsupport.com/Remote-Control-Base-1L
The correct wall pack adapter for a CAB1L blue base 9V 500mA AC
