Swap Modicon 984-685 for 984-785

100% of my Modicon experience has been on the 984-685. We have several of them still in operation. As you probably know, new 984-685s are getting next to impossible to come by. Can a 984-685 be replaced by a 984-785 as a virtual drop in replacement? What issues can I expect to see if I make a change out?

OR...
do you know anyone who is selling new 984-685s?

Drop in and go.

We have held a 984-785 as a spare for our plant for several years.
We have one 984-785 in use, and many 685's. It is pretty much a case of download your program and drop it in.

Currently, however, we are replacing the 984 CPUs with Quantums, except for a few lines which we expect to decommission soon.
Three years ago, our Modicon supplier would offer us $1,000 per decommissioned CPU that we sent back to them, now they have so many from others doing the same thing, that they no longer want any more.
We will soon have a supply of old, second hand but still good 685s available.

Second note, new 785s will soon also be un-available (from the end of June). We have been told that the last date for taking orders is around June 15, although you should check this. This is the main reason we have undertaken to upgrade to Quantums. (The other main reason is Profibus).
Our supplier will continue to repair all 984 items for the forseeable future, but we don't know how long that will last.

My suggestion is to contact your Modicon supplier ASAP to check out your risk.

Thanks for the info guys. I found someone selling a 785 for a rediculously low price. He claims its good. Apparently completely clueless as to what he has his hands on. When I found that I figured it was a good time to get a spare.