Email Wayne Renga at jandwelectronics@yahoo.com
Wayne installed a board and a chip from a 1997 MTH Railking Southern PS-4 in a 1994 MTH Premier PS-4 I had purchased from a Forumite. That provided Passenger Station Announcements (PSA) and enabled operation with modern transformers. Now I have the best of both worlds - a model of 1401 in the Smithsonian that operates on current transformers.
Wayne can provide expert advice about installing PS-1.
I highly recommend purchasing and installing a BCR from Wayne. Apply 10 volts for 1 minute and a PS-1 locomotive is good to go. No worries or possible damage from a depleted or a dead battery.