Problem with a MESA 7i76

I've checked the dir outputs: for the first four motors the outputs don't switch (always at 5V), while the dir works for the fifth motor (switch correctly from 5V to 0V and viceversa).
The 7i76 is new, I really hope it's not damaged!

did you check the + and - outputs?

I currently don't have an oscilloscope. Is there any other way to check these outputs?

Measure the + and - outputs to ground with a voltmeter

Ok they are all constant to 5V.

Also you can check the outputs by verifying that they change state when LinuxCNC starts.

The + outputs should all be in the high state and - outputs all in a low state when LinuxCNC
is not running. When LinuxCNC is running (and idle) all of the + step outputs should be low
and all the - step outputs should be high.

If the + and - outputs are both at 5V relative to ground, then its likely the 7I76 has been damaged (or you are not reading the outputs correctly)

Hi everyone sorry for the delay, we have checked what you asked: for the TB2 the + and - outputs are all at 5V constant, so probably the board was damaged. Thanks again for all the fast feedback.

Sorry to hijack the thread, but it was so similar and recent it didn't seem worthwhile to start a new one; I have the same symptoms of stepgen 0-3 not working on my 7i76, but no complaints of any kind from my 6i25 (in a new Dell box, replacing the 5i25 from this thread: forum.linuxcnc.org/27-driver-boards/36634-5i25-deterioration) during LinuxCNC startup.

The only difference is on mine the TB2 block pins alternate 0V and 5V during power-up, rather than being all the same, but with no state changes on PncConf testing or LinuxCNC jogging.

I set PncConf stepgens 4 and 5 to mirror the X axis on stepgen 1, and started running the axis test. Every + step pin on TB2 remained at 0V, every - pin at 5V, but the + step 5 pin on TB3 scoped as the expected square wave that I used to get when the mill was working (all I did was move the electrical cabinet and rewire with routing and crimp terminals!).

I just bought a new 7i76 to minimise downtime, but would you agree that here too it appears that the two TB2 chips are damaged? If so, how much would you estimate it would cost to replace them at Mesa so I could keep this board as a backup? The field voltage and logic all appears to still work just fine (I have ENA lines on TB6 outputs 0-1-2, no spindle control as yet).

If the +STEP and +DIR outputs are high (5V) until LinuxCNC starts and then go low,
that means that they are OK, Likewise, if the -STEP and -DIR outputs are low until LinuxCNC starts and then go High, that means that they are OK.

This suggests the problem is elsewhere (firmware, hal setup etc)