Retrofitting a 1986 Maho MH400E

I am a little confused by MESA's instruction for grounding the analog drive control wires shielding...

7I77 14
OPERATION
ANALOG SERVO DRIVE INTERFACE
The 7I77 provides six channels of +-10V analog servo interface on connector TB5.
Minimum load resistance is 2K Ohms. Normally analog servo drives use differential inputs
to avoid ground loops. Suggested wiring is shielded twisted pair with 7I77 AOUTN to drive
AIN+, 7I77 GNDN (adjacent to AOUTN) to drive AIN- as the twisted pair and 7I77 GNDN
connected to the shield at the 7I77 end only. The drives common or GND signal should be
connected to the 7I77 power GND with a separate wire.

That the +10 / -10V wires for the first axis connect to TB5-3 (GND) and TB5-4 (AOUT0) is clear, if somewhat confusingly named. But do I also connect the shield to TB5-3 (GND) or do I connect that to the 7i77 power ground along with that separate wire coming in from the Indramat ground?

I am going to use CAT 5E, as it good quality shielding, and I have some. I plan to run three separate cables, one for each axis, or would it be better to use only one cable with a twisted pair for each axis and common shielding?
Mrk

Do the drives have differential inputs?
if so the wiring is

AOUTN --> AIN+
GNDN --> AIN-
GNDN --> CABLE SHIELD (7I77 end only)

Drive GND --> frame GND

So that means I connect both the AIN- and the shield together into TB5-3? Seems weird to me.

I found this in google.
forum.linuxcnc.org/media/kunena/attachme...ALOG_REF_CIRCUIT.png
so I guess the do get wired together.
Mark

I made the three +10/-10V cables. Now I have a question about the Indramat gound. The Indramat terminals have three ground connections, one for the shield of each axis cable (MAHO terminated the shielding in three places - The Indramat, the Phillips connector and in the middle of the cable to the Phillips housing).


The three axis grounds have continuity between them. Should I run three wires to the 7i77 field ground or just one?
Mark

First motion of the X Axis...


Somewhat lacking in action

First I had the encoder counting backward but made the encoder_scale and Output_scale negative as per another thread here, but I still just get a 3-4mm jerk and a joint error as soon as I enable the machine. I've attached the HAL and INI files, and would appreciate if someone can spot the error. The machine has the original Indramat drive and motors and I haven't touched there settings. All three axis are nice and stable and solid without the +10/-10V cables from the Mesa connected. If I try and turn the pulleys the Indramat resists.

On another front, I used the hal scope to test all twelve gearbox position inputs and outputs, which are now correctly wired.

John, I tried again to load your latest gearchange.clp into classic ladder, but still get a load failed error. My classic ladder installation is otherwise functional. When I open your file in wordpad, it doesn't look obviously corrupted.

If it runs away on enable, that most likely means that the feedback is backwards
(so you have positive rather than negative feedback)

If the encoder (DRO) reads properly, the fix is to change the sign of the analog output in HAL