I am confused about what you did without a picture of the Williams board, but if you did what I think originally, you had the ERR Sound board connected to a motor take off on the Williams board which is probably what was causing erratic bell/horn. That other port is a little unknow about what comes out of it.
Typically, you splice directly into the leads coming off the pickup rollers and the chassis ground. Sometimes Williams reverse wire color from the traditional red is pickup roller, black is chassis. But that is the most reliable method. I do realize you might have had to cut the wire to splice it.
You never really stated clearly where you where getting AC power from for the ERR board in your original post. Which I think is why you had use confused. G
