1756-if16

diat150

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Mar 2006
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Louisiana
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Having a weird issue.


card setup as single ended no alarm, float data. all channels 0-20ma and 0-100%



all of the rtn and rtni jumped together on the right hand side of the RTB with a single rtn on the left hand side of the RTB brought to -24volts


channel 12 is staying maxed out when the rtb is plugged in.


scratching my head on this one. seems like the card is wired right unless I am missing something.
 
Last edited:
The only thing that bothers me about your post is "brought to -24volts"

Some 24volt power supplies to if fact have +24volt 0volt (common) and -24volt terminals.

Hopefully it is (rtn) connected to the 0 volt (common) terminal of your power supply.
 
Last edited:
The only thing that bothers me about your post is "brought to -24volts"

Some 24volt power supplies to if fact have +24volt 0volt (common) and -24volt terminals.

Hopefully it is (rtn) connected to the 0 volt (common) terminal of your power supply.

Yeah. Misspoke on that. It’s going back to common.
 
Having a weird issue.


card setup as single ended no alarm, float data. all channels 0-20ma and 0-100%



all of the rtn and rtni jumped together on the right hand side of the RTB with a single rtn on the left hand side of the RTB brought to -24volts


channel 12 is staying maxed out when the rtb is plugged in.


scratching my head on this one. seems like the card is wired right unless I am missing something.

Is channel 12 maxed without the RTB plugged in?

This happens when the channel has failed and the internal 249 ohm resistor is open circuit.

You can check the voltage on the terminals (when the RTB is plugged in), it should be 1V for 4 ma, 5V for 20 mA. More than 5V (normally about 23V) shows a failed internal resistor on the 1756-IF16.

If that is the case, you can ship it to Rockwell for 'repair'. You get a new board inside your original case, but it is 'new' and not 'rebuilt'.
 
well It looks like the issue turned out to be the TBS6H push in terminals. Our fault on that, instead of running 2 common wires we pushed two of the metal terminal jumpers into the same terminal to make the whole right side of the RTB common. Apparently that puts a strain on terminal 29 and it doesnt make a good connection. Just so happens terminal 29 is channel 12 rtni. So the solution is to jump 1-25 then jump 27-31 on the right side and run common to 10 and 28 on the left side. We just swapped to using the push in RTB so dumb mistake on our part.
 

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