[MikeZ]

Like any other item of complicated electromechanical equipment, what Bob said is true, like if it ain't broke, don't fix it.

I think the more appropriate way to look at it for Sten and others facing the same issue is one of putting good money after bad.

Even if one bought the S-tec on credit, I'd wager that the payments would be less than the ongoing repair and maintenance costs for the old (renovated) 400 autopilot. Not to mention downtime and aggravation.

So its a personal decision after all.