Hi @flightmaster
Seems as though you may have damaged something in the power supply circuits on the systemboard.
A 1 long, 2 short beep code indicates a systemboard, LCD display or memory problem. A bit vague but given the LCD is dim it seems like a power issue
Here's a link to the [https://www.alisaler.com/ibm-thinkpad-x220-x220t-dasher-1-h0227-schematic/|schematics] that may help.
You may have to start by checking the various voltage supplies on the systemboard to find out what's wrong, unless of course there's obvious component damage on the board. If there is then the schematics will help as they show the component values or model number for everything on the board.