PLC 1769-L33ER logic to 1747-L552 logic

Hey everyone,

I am having trouble figuring out where my problem is in the logic.
I have two identical PLC programs, one in 1769-L33ER and the other in 1747-L552.

i made a change to the code on 1769 and works fine but when i applied the same logic changes to 1747 PLC i keep getting two outputs ON at all time (please see the highlighted attachments)

its basic logic changes that i made input and output and one timer.

thanks for any help,

best Regards,
Sam

Your question is too difficult to answer because there is not enough information to solve. You might be better off posting a .zip of your logic and asking for others to help troubleshoot that. l will note however that anytime I want to troubleshoot why an output is on when I think it shouldn't be, I use bits that I create like "Always_OFF" in different rungs/branches to try and isolate what code is active and figure out from there which one is keeping my output on.

Also keep in mind that very often the RSLogix software isn't updating the User Interface quickly enough for you to see a transition if it's happening super fast. The best bet is to block off sections of code from executing with an Always_OFF bit and one at a time remove them.

Make sure you're not doing any MOV or COP commands whose destinations would be encompassing your output address... meaning if you're moving a large value to the output word somewhere, make sure its not overflowing into the address in question.

While there are MASSIVE differences between the SLC 5/05 (1747) and the CompactLogix (1769), Logic is logic, it should not change between PLC's the concept is always going to be the same.