Mesa 7i76e Malfunctioning

I have been using my Mesa 7i76e on my hobby machine for just over a year now. I believe the last successful use was just over a month ago.

Two days ago I powered on the machine for a job. First step is to home the machine. I opened LinuxCNC and this was the result:
X (Joint 0): Began to move for approximately an inch before stuttering and "grumbling" to a stop
Y1 (Joint 1): Began moving in the incorrect direction at the correct speed
Y2 (Joint 2): Began moving in the correct direction at the correct speed
Z (Joint 3): Homed perfectly

I have NOT made any wiring or configuration changes (HAL, INI) since last successfully operating the machine. I regularly make backups of all of my configuration files - every couple months or if I wanted to make a settings tweak. I have checked 3-4 prior working backups and the machine behaves exactly the same despite which configuration I use.

My first suspicion was the PC. I am running a Dell Optiplex 380. To rule this out, I flashed my Raspberry Pi 4 with the latest LinuxCNC image and moved my configuration files to it. I configured the static IP for 10.10.10.10/24 and plugged into the Mesa 7i76e. It connected no problem.

Now using a Raspberry Pi 4, I attempted the same homing sequence. The results were exactly identical as with the PC (not good). At this point, that leaves either the Mesa board or the drivers. I have not yet tried changing the drivers because it seems extraordinarily unlikely that two have failed together despite not having any previous issues...

I do not know how to definitively identify what may be wrong with the Mesa board. I see the manual mentions a JTAG interface, but the connectors I'm finding are ~$60.
Is that even a worthwhile purchase?
What software would I use it with?
What diagnostics are available?

I'm a bit bummed that the board may have failed after 1.5 years.

 

Sounds like marginal step/dir signal levels. Another possibility is step
drive power supply issues.

I would first  check the DIR signal levels at the drives (by jogging in either direction)
Both the DIR+ and DIR- should swing from close to 0V to close to 5V  when changing
direction  (Less than about 1V when low and > about 4V when high)

Also for low end step/dir drives, I would use single ended connections
rather than differential.

JTAG is of no use in debugging signal level/external interface issues, its really only
useful for initial programming of the card or recovery if both EEPROM images
have been corrupted.
 

@ PCW: I performed those tests this afternoon. Since the machine must be homed prior to jogging, I went into the INI file and commented out the "HOME_SEQUENCE" numbers. This allowed me to jog without homing, with one caveat: Joint 2 (Y2) - the motor that worked seemingly correctly when homing - is not changing value on the gmoccapy GUI when I try to jog. What I mean is, I do not think Joint 2 is actually being commanded to move with the keyboard. No big deal, I was able to get data for the other three drivers.

The results were as follows:

 

Another thing I checked was stepper drive voltage (power supply) and confirmed that it is at the nominal 42V.

@tommylight:

When you say isolate, you mean to avoid them touching the circuit board on the underside? I checked very carefully today to make sure that has not occurred, and they have a reasonable clearance below. Nonetheless I think that's great feedback and I will wrap the end of the insulation (and the foil) with electrical tape just to be sure.

I did try switching the DIPs back and forth to no avail. I also tried a new driver on the X axis and no change. I think per PCW's recommendation I am confident the drivers are doing what they are told.

That looks to me like the DIR+driver chip is damaged
(Its U19, a 74ACT541)

In any case the + pins must be in the opposite state of the - pins
if this is not the case, its very likely a driver has been damaged.

I do have a rework station if it comes down to that, but an expensive experiment to try...

At the risk of sounding entitled, do these things come with a warranty? Is there a way I can perhaps ship it back for testing/confirmation/repair?