I am here, but i got lost for little bit. Unfortunately, I don't own a oscilloscope right now. I would like to possibly rent or borrow a digital one from someone. Anyone in Central Jersey?
Even with a scope, I will not get all the information I need to solve the problem. As it occurs in the field on different types of machines by different manufactures.
My goal is to make the circuit as robust and simple as possible as this circuit is going to be added board that is already populated.
Right now, It looks like am going to continue to use the 74LCX245 and change the cap size of the original circuit to largest size I can find. Use a Unidirection TVS and decrease the pull-up resistor size, and may be and a series resistor. This set of changes will be the easiest to make. http://www.jernie.com/old.pdf
I will test this circuit in the field for a little bit and if it starts failing. I will add polyswitch or varistor and opto-isolator.
One new question for me is that footprint of the cap circuit is a 1206. Finding large capacitors is easy with digikey but is it better to select a componet with larger Capacitance and lower voltage-rating or the other way around. for example
1uF @ 100V
4.7uF @ 50V
10uF @ 35V
22uF @ 16V
47uF @ 6
http://www.jernie.com/old.pdf