7i78 Joint 1 and 2 no longer working

I am using a 7i78 to run some DMM servos in quadrature position mode. I have not run had the machine on for a bit over a month and when I shut it off it was working fine. I have been working on the spindle and motor system and have not touched any of the motion controls.

Today when I turned on the machine:
X (Joint 0) moved fine

Y (Joint 1) moved but not correctly, it was "stuttering" almost like a wire was loose. I have seen similar movement when I had a short in the step/dir wires on a different machine. It worked like this through a couple power cycles then stopped completely

Z (Joint 2) didn't move at all

After going through some trouble shooting (checked wires, checked for noise, checked connections, checked the board for signs of shorts) I was able to get all axis to move as long as they were plugged into the step/dir for Joint 0 on the 7i78. No axis would move when plugged into the joint 1 or 2. I did not try joint 3.

My thoughts are that I have a bad IDE cable from the 7i92 to 7i78 or perhaps the 7i78 went bad but both seem unlikely since it was just sitting here. Any thoughts on where and how to trouble shoot further?

Included hal and ini in case something was corrupted or fat fingered.

I would check the 5V at the 7I78 and that the step and dir pins swing about 5V


You can check the direction pin swing by jogging in both directions
You can check the step pin swing by measures the step output when linuxCNC
is loaded (and idle) vs when linuxCNC is not running

5v to the card is good. I did find some interesting results when checking the step/dir pins. Since this is in quadrature the behavior was different then you described but I found:

Joint 0 step and dir pins both swung from -4.7 to 4.2 when jogging

Joint 1 step pin swung from -5.5 to -6.2 when jogging (LCNC off was -4.65)

Joint 2 step pin swung from -5.5 to -6.1 when jogging (LCNC off was -4.45)
Joint 2 dir pin swung from 0 to -2.2 when jogging (LCNC off was 0)

Is this pointing more to an issue with the 7i78 or 7i92? The only thing connected to the 7i78 are the 3 sets of step/dir wires and the ide to the 7i92.

2.2V indicates a damaged driver chip

Sorry no 2.2V makes sense when moving and you are using quadrature
since you will have a 50% duty cycle (square wave)

All the outputs should read be about 5/2 or 2.5V when moving
relative to ground since the should all be ~5V square waves

Whats the turn around time for a repair these days? Is it even worth it?

U5 or U6 are the driver chips and are inexpensive but require
SMT repair skill to replace. Mesa can repair these but turn-around
may be a week or so

If you actually have 6V anywhere this is the likely
cause of driver chip damage. Neither the power supply or
any step/dir pin should have a voltage outside the 0 to 5V range

The card has very few things running into it. What are the possible sources of the 6v. Nothing plugged into it besides the ide is carrying voltage. I would hate to replace a card and blow it again.

5V supply?

5v supply is sitting at 5.07

I did check the cables going to the servos and each of the step +/- has a small amount of voltage coming off them when they are disconnected from the 7i78. The dir pins do not.
Joint 0 is fluctuating between -.13 to -.19v
Joint 1 is fluctuating between -.13 to -.17v
Joint 2 is fluctuating between -.23 to -.57v

I did narrow it down to it coming directly out of the servo drive so it's not noise or bad wiring.

Any thoughts on this?
photos.app.goo.gl/QvVNPYJjumfW3kTw9
Video of the meter