7i77 encoders not working

I would try with the 7I77 jumpered for TTL and with the /A, /B,/Z disconnected
(since they look to be TTL encoders not differential)

I would then check that you have close to 5V swing on A,B,Z when in TTL mode

The reason some channels work is that you signals are wrong and just barely large enough to overcome
the hysteresis of the inputs

If they were working, you would expect at least 2V (more likely 3 or 4V)
in one state and -2V (again more likely -3 or -4V) in the other state
measured across A and /A, B and /B and Z and /Z

I wonder if an92626 ever found a solution to this problem?

I am facing a similar issue with the machine I'm currently working on. 7i92+7i77 running on 2.7.14 - Debian Stretch. I changed everything around in trying to find the defective wiring/encoder but in cannot get enc0 and enc1 on the 7i77 to work. b input remains dead on those two. I have even changed the a and b inputs on the terminal at the 7i77, and still b phase show nothing. wired a different encoder (new, that I checked on the oscope as well), still nothing on b.

If I plug the same encoders into enc2 - 5, it works as it should.

going to change the 7i77 later today as a sanity check.

Henk

"b" on encoders 0,1 not working suggests a common problem on the
multiplexed "b" signal connection between the 7I77 and the 7I92.
This problem could be either on the 7I77, the cable between the 7I92 and 7I77,
or on the 7I92.

Thanks PCW. I will test some different components to try and isolate the problem.
Henk

So it turned out that the ribbon between the 7i77 and the 7i92 wasn't crimped properly ..
Thanks again for the advice PCW.

Henk