Encoder started misbehaving

Today something strange happened to my setup. I was tidying some cables up in the control cabinet and must have fried something.
I have been running my machine for about a year now without any problems. 
Now my Y encoder readout follows my X axis. Even when I disconnect the encoder from the 7i77 it happens.
Changing from hm2_[MESA](BOARD).0.encoder.01.position
to hm2_[MESA](BOARD).0.encoder.04.position (and updating the other encoder lines from 01 to 04) and plugging it in encoder 04 position did not work.

X Z still works though. Spindle encoder reads nothing, although the actual encoder is functioning.

Have i fried my 7i77?

/Peter

If the input to encoder channel 0 affects the count on encoder channel 1,
that suggest a problem with the encoder multiplexing (basically that the encoder
mux-sel signal is not getting to the 7I77) 

This could be bad cable, or cables not inserted fully, bad or damaged
5I25, or bad or damaged 7I77.

You can check the 5I25 for damage by

1. Disconnecting the DB25 cable (with all power off)
2. Running: 
sudo mesaflash --device 5i25 --rp 0x1000

This should report all highs on the I/O pins = 0x001FFFF

To diagnose the 7I77 encoder issue, I would setup halshow
to watch all 6 encoders and then try each encoder input and see:

1. If it works
2. If it affects any other channel
 

Thanks for your reply!
5i25 reported as you said 0001FFFF

I also tried with another cable without any change.

Encoder 00 and 01 show the same value, although nothing is attached to 01.
02 & 03 seems to be paired as well.
I got different reading on encoder 04 & 05, but they both changing from one encoder input.

Any further troubleshooting tips are highly appreciated! I am comfortible scopeing/soldering SMT if you think this is repairable.
/Peter

Basically as I said before, this points to an issue with ENCMUX. 

It may be a damaged 7I77 buffer chip for this signal
or in may be an on board 7I77 issue. The ENCMUX
signal is om DB25 pin 17. 

A 5i25 problem is still possible but less likely (damaged I/O pins
tend to be stuck low so can be detected with the simple mesaflash test)

I would definitely scope/trace the encmux signal.

As to what caused the damage, disconnecting/reconnecting the DB25 cable from the
7I77 if there is an (even small) ground potential difference between the PC and the machine
can damage interface components so should only be done with all power off.

Tomorrow, I can look at the schematics and see what parts on the 7I77 are in the ENCMUX
signal path (I think just one Hex inverter)
 
 

Thank for the help!

As to what caused the damage, disconnecting/reconnecting the DB25 cable from the
7I77 if there is an (even small) ground potential difference between the PC and the machine
can damage interface components so should only be done with all power off.

That's probably what happened, definitely my screw-up!

Tomorrow, I can look at the schematics and see what parts on the 7I77 are in the ENCMUX
signal path (I think just one Hex inverter)

Thank you!

/Peter

Looks like 7I77 U15 (74LCX04) receives, buffers, and inverts
the ENCMUX signal to generate the EVEN/ODD signals that
enable the 26LS32 even and odd line receivers, so is a prime
suspect with encoder mux issues: