Retrofitting Maho MH600E 1989 - Meas 5i25 & 7i77

when i hook up my oscilloscope it shows something between 2,8V and XX. cant read due fast switching. Guess thatś ok too.

You would expect a clean 3.3V at that pin

If its really noisy it suggests a grounding or EMI issue

BTW the 3.3V pin on the programming header connects directly to the PC 3.3V,
be _very_ careful that you do not short it to ground

Will LinuxCNC run if you disconnect all 7I77 encoder and analog connections?
That is, anything that connects to the MAHOs ground. You may also have to
dismount the 7I77 if its bolted to a control box frame (the 2 mounting holes on the
DB25 end of the 7I77 are grounded)

Also is the PC in a case?

(I suspect a ground loop)

I ve disconnected the encoder pairs one by one to see if one of them is causing the problem.

[strike]Pair one did no change
Pair two did no change
Pair three seems to be affecting my problem.[/strike]

Itś the direction pair. When its disconnected the PC doesnt crash. its on since last post with linuxcnc running. no crash.

When i check with the osci it shows some ttl signal but Vmax sometimes goes to + or - 14V
If i try to check that voltage with the multimeter it only shows 3.2V more or less.
The 12v seems to appear when i start turning the axis.

I ll investigate. :>

EDIT 1:
saw your complete last post now:
quick reply.

Only 5v to TB1
24V to TB8 (the orange one) not sure about the number right now
and 3x encoders on the top row, close to the db25 cable.
Maho not connected only ground connected, mains off.
pc is laying on the floor on cardboard xD
7i77 floating midair

EDIT 2:
Linuxcnc was running for like 35 Minutes without crash and the direction pair disconnected. then the pc crashed again.
Iḿ now at a point where every pair is removed and only 5v and 0V is connected to the encoders. Every other combination failed.

Right, if its a ground loop issue, 5V and ground connections to anything on the MAHO are the issue

Okay now that are all connections:

5V PSU to TB1 -> 5V and GND
24V PSU to TB2 -> 24V and GND

TB2 NC -> shielding of the cables of scales
DB25 7i77 >-> DB25 5i25

TB3 Pin3 -> 0V Exe card channel 1
TB3 Pin6 -> +5V Exe card channel 1

TB3 Pin 11 -> 0V Channel 2
TB3 Pin 14 -> +5V Channel 2

channel 3 same setup.

This seems to work so far, no crash since 30 minutes

EDIT: when i unplug the 5v psu the pc crashes sometimes too, thatś new...
EDIT 2: connected one scale...worked fine for 30 Minutes
connected another one, worked fine for 15 minutes.
wanted to edit this post to report good progress and booom crash

So all electrical components are run from one multi socket thingy. the only extra ground run is the one from the 24v PSU to the TB2 socket.

You might check to see if the 0V on the 5V, 24V or EXE units connect
to frame ground

Also I am assuming 5I25 W2 is on the down position (it should be)
And 7I77 W5 is on the right hand position (it should be)

Is the PC in the control case with the 7I77?

PCW wrote: You might check to see if the 0V on the 5V, 24V or EXE units connect
to frame ground

Also I am assuming 5I25 W2 is on the down position (it should be)
And 7I77 W5 is on the right hand position (it should be)

Is the PC in the control case with the 7I77?

gonna check tomorrow if one of these connects to frame ground
W1 and W2 down
W5 is down if db25 is top

So I could verify today, that the 5v from the 7i77 to the EXE card doesn´t seem to be the Problem. When only 5v and GND/0V is connected to all three exe ports it´s running stable.

So only Ua0 Ua1 and Ua2 are left for causing me trouble.