MRC 1400 repair and upgrade

[Ted Lewis]

Ruined the pot in the unit by doubleheading Bowser K4 Pacific's pulling 20 Ulrich metal cars.
The POT is marked R1378817
The Regulator(?) Chip is marked
D1192
8B3
Replacing the pot would be easy but
Can anyone advise me about choosing different components which would give a higher amperage output?
Thanks

 

[Iron Horseman]

Since Radio Shack went under, I've been sending people to Mouser https://www.mouser.com/ And Jameco This is a 5 watt seems to be the largest they have https://www.jameco.com