Older Williams SD-40

[phillyreading]

How do you hook up a bridge rectifier in an older Williams SD-40 or SD-45?
It has twin motors and a blue circuit board, maybe 12 years old.
Lee Fritz

[3railguy]

Depending on the rectifier, in most cases, there should be a lead on the rectifier with a + (posative) sign stamped next to it. That lead and the lead opposite of it go to the motor leads. The other pair of leads go to the center rail and ground to the frame. If the engine goes in the wrong direction when you hook it up, reverse the motor leads, not the track power leads. The rectifier should be rated 3 to 6 amps (3 amp min) or you could fry it.

[phillyreading]

John,
Thanks for the help! That worked, now able to run only forward which is what I wanted.
Also Williams advised using an 8 amp rectifier, but didn't say how to wire it.
Lee