Atlas S1 Switcher
This loco runs good with Dither (digital pulse power) setting of CV56=3 and CV57=25. The M1 decoder was hard wired into the circuit board supplied with the loco, it easily fits because of its small size.  The M1 decoder  fits nicely in the cab area.  To see this installation in the Atlas S3 locomotive click here. The Atlas S3 uses a newer type lighting board and and is a slightly different installation. Important: to remove the shell the cab must be removed first. Remove the cab by gripping it at the bottom on one side and pull it away from the frame while lifting up. After the first side is un hitched do the same to the other side. The cab will lift straight off then. After the cab is off the long hood comes off easily.  Important: there is a 2-56 screw in the bottom of the loco that must be replaced with a nylon 2-56 screw to insulate the motor from the frame. This is important to prevent damage to the decoder. See photo below showing bottom view of the loco regarding this.

                               

Click on photos below to enlarge and read more information.

 

        

Due to the tendency of the rivet holding the motor tab to the gray wire pad to grow weak we would advise soldering the gray wire directly to the top motor tab to avoid intermittent or non-existent connections with the motor.