When I got my Model 28, I noticed that the Select input didn't seem to be working correctly. At the time I figured the voltage I was putting into it wasn't the scale that it wanted and reminded myself to check it out later (I was trying to have fun after all, not debug stuff).
Well, it turns out there is something wrong with it. Peter posted to the yahoo group notifying us that the first 15 units shipped with a mis-programmed microprocessor which handles the switching of pulses based on the voltage in the Select input.
Basically those of us with these Model 28s have to send back the microprocessor for re-programming. Not a huge deal I guess. Hopefully I'll be able to still use the other functions of the Model 28 without it...but I'm kinda doubting that.
Click the link above to see the post on the Yahoo group.