Replacing Advanced Motion Controls "brush type 12A8 with "Axcent" amplifier

Todd, thanks! TB3 positions 1 & 4. So TB3 1 went to position 4 w/o the original lead (so the encoder and drive leads stay together) only to different locations on TB3 1 and 4. I have tried the new diagram, now no motion at all. If you try "jog" the velocity in DRO shows correctly the feed rate, but no motion. The yellow "shows the tool movement on DRO screen" does show motion, but table does not move.

many thanks

So pin 7 (the drive) & pin 3 (on encoder) stay with each other, and move from location 1 to 4 on TB3, and reverse happens to mating leads 4 to 1. This is looking at pic of diagram at prior post dated 23 Nov 2020 19:03 (5 posts earlier!)

many thanks

Todd wrote:

What leads did you move where on which axis' drive? It is impossible for us to keep track of what you are changing because you never precisely say what you are changing. Just swapping things willy nilly is going to lead to blown up components.

Todd, Many thanks for all your continued support!! What may not be so obvious to those who follow this, is that I am working and have been working with AMC engineers, if I have a question that AMC should support that maybe the members of the forum are not familiar with I ask them. Currently I have asked for a valid/real diagram of how leads are to be routed for this application. I am hopeful that I will receive news late this morning. I tried to attached are the pics but were too large, there was little to see really.

Many,many thanks, to all the members.

Many thanks, to Todd and all the forum members. This attached diagram is what AMC suggested, the only change is the driver (P1 pin 5 goes to pin 2 ). I have incorporated this change and Y axis "runs away" (does not matter if SW1-6 is off or on) and X axis has no resistance to motion, RED LED is on drives. The AMC engineers have no more help to provide, the problem is on the controller side they say. I am wanting to go back to the 12a8, and use back EMF as the form of feedback for velocity control. I warmly welcome any suggestions.

many thanks

The original 12a8 drive should be capable of adequate performance, the new drive with it's additional encoder feedback should have been better. However the difference should not have been enough to justify buying the new drive if your old one still worked. That said I'm not sure you may find any improvement by switching back, because we still don't know what the problem is. Is it possible there could be a problem with the motor? (failing brushes or some sort of problem with the commutator or windings?) I'm grasping here because I just don't have a clue.

Many thanks! This is test that AMC has suggested, to make sure the drives are functioning properly in encoder velocity mode, and to figure out which position SW1-6 should be in on each drive. This test will not involve the controller.

For this test you'll only need power, the motor, and the encoder connected to the drive. This should be done with the motor disconnected from the machine.
The motor may run away during this test, so it's important that the motor is disconnected from the machine as it could be dangerous.

Start with nothing connected to the drive.

1) Before powering on the drive, set the switches as follows: SW1-1 OFF, SW1-2 OFF, SW1-3 OFF, SW1-4 ON, SW1-5 ON, SW1-6 ON.

2) Connect the power and ground to the drive, but do not connect the motor. power on the drive and make sure you have a green LED. If you have a green LED, power down and continue. If you have a red LED, double check the switch settings in step 1.

3) With the drive powered down, set potentiometer 4 to the middle of its adjustment. This is done by turning it clockwise 14 turns, then turn it back counter-clockwise 7 turns.

4) Connect the motor and the encoder wires to the drive. The encoders will need power and ground to work properly.

5) Now you can power on the drive again, but be ready to shut off the power if the motor runs away at full speed. If the motor does not run away, proceed to step 6. If the motor does run away, power down the drive and set SW1-6 OFF. Make a note of which way you have SW1-6 set for the motor to not run away. Once you have this setting it should not need to change.

6) If the motor is not running away, make sure that you can turn the motor in both directions by adjusting potentiometer 4 in either direction.

7) Turn potentiometer 4 back to the middle so that the motor is not moving, and then power down the drive.

At this point you can set SW1-4 back to the OFF position to set the drive back to offset mode. Then reconnect the drive and motor to the machine.

Repeat this test for both drives, one at a time.



This is what I observed after set up:

I have released the e-stop with SW1-6 ON (both x & y axis), POT 4=7 turns (as per directed) and Red LED is on, x motor is very slow rotation; y motor very faint oscillation. Adj POT 4 (on x axis) to change direction of x motor and as soon as direction of motor changed, Green LED came on BOTH axis at the same time. Y axis motor speed up to medium speed "run away".

POT 4 (on a axis) will make Red LED go green, 3/4 CW of turn max, from mid point.

Now with sw1-4=off on both drives; (X axis sw1-6=on; Y axis sw1-6=off) release e-stop and start linuxcnc; DRO is moving (F1 down & F2 grayed out) x & y motors are slow moving; F2 down, DRO stops (motors stop), & F2 up, DRO moves & motors move. I have homed axis, cleared DRO and ctrl K (to clear trace from screen) and when motion starts yellow trace moves from 0,0 towards to lower right side of screen. When motors are in motion they resist tiring to stop motion.

When F2 is down red LED will appear on both drives.
X axis SW1-5 & 6 = ON
Y axis SW1-5 = ON

It appears the F1 & F2 are reversed; now if you have F1 & F2 up the motors are NOT free to move (green LED), F2 down Red LED on and no or very low resistance to moving. I turned POT4 (approx 1/8 turn) to try to stop all motion (there was some very slow movement) in motors, it appears ok. I am still in contact with AMC.

After AMC suggested that sw1-5 is only for set up, needs to be off. Currently x axis is set all off, except sw1-6=on; y axis all are in off position, changing does nothing for "run away" in this axis. I still have belt off for that reason. The only time Green LED is on is when F2 is down and before the motor errors out, so for very short time. So can't get to tuning screen with motors under command.

Many thanks!

I want to thank Todd Zuercher, tommylight, JR1050, PCW, OT-CNC, A-M-C support & the Moderator, piasdom for all the help and continued support. This was not a successful conclusion to the project, I do not believe there is anything of value to be found here with the exception of the procedures offered by A-M-C support were valid for testing that part of drives.

Please allow this post to disappear if possible, nothing of value can be found here!

Many, many, thanks to:

Todd Zuercher, tommylight, JR1050, PCW, OT-CNC, A-M-C support & the Moderator, piasdom for all the help & support.

I have been off the forum for a while and lost track of this.

Looking over your pdf, you have the analog drive connection wrong.
You need to connect the 7i77 TB5 pin3 ground (neg ref) to the AMC signal connector pin 5 -ref input. (circled in red on my attachment)

If the encoder isn't reading try connecting encoder ground with pin 2 on the AMC.

Last, I'm not entirely sure on the enable in case that is not working for you. Double check with PCW as reversing can damage your 7i77.
I marked in red what you could do with a switch pin9 to ground to enable or disable the drive (logic is dip switch dependant).

I'm going off your earlier posted AMC manual not sure if anything changed since.
Hope this helps

OT-CNC, Many, many thanks!! I am ever so grateful for your help, but I have sent back and asked for return of the new AB15A100s. I have a set of AB15A100 (these were from ebay, have no history, so I thought it was me when could not tune, so that is when I ordered the new AB15A100s from A-M-C that I just returned) that I would consider (the ebay ones) if you feel up for it. As if that was all that is going on, I have on the way a set of 25A8Ds with A-M-C power supply from ebay (should be here 12/13) for backup.

I am very grateful for all the wonderful people on the forum and the expertise that is so spot on. I do not want to wear out my welcome and one reason I went back to proven solution, the 12a8s, for my application.

Many thanks!

Edit: This is new 7i77 card, I have been ever so careful not to do anything w/o advise in reference to this new card; it was not so obvious but AMCs engineer was advising or a member of this forum. I am tiring to be careful, because; "PCW says reversing can damage your 7i77" .

Edit01: Attached is diagram as I understand it, option 02 in dotted or option 01 (OT-CNC, if possible please read, what I think you have written, to see if I have it correct) pin 9 to pin 11. It will be option 1 or 2; not both. I am willing to try this just want to verify the diagram. 1st I will try this with ebay drives, to test as per earlier (AMC suggested a way to test drive w/o controller, that will turn motors both direction by POT 4) described in earlier post. If any success here and I will report back, if this fails, the 25A8Ds are on the way. Thanks!!


Many thanks!!

This is the test that I have done on the x and y axis, one at a time.

1) Before powering on the drive, set the switches as follows: SW1-1 OFF, SW1-2 OFF, SW1-3 OFF, SW1-4 ON, SW1-5 ON, SW1-6 ON.

2) Connect the power and ground to the drive, but do not connect the motor. power on the drive and make sure you have a green LED. If you have a green LED, power down and continue. If you have a red LED, double check the switch settings in step 1.

3) With the drive powered down, set potentiometer 4 to the middle of its adjustment. This is done by turning it clockwise 14 turns, then turn it back counter-clockwise 7 turns.

4) Connect the motor and the encoder wires to the drive. The encoders will need power and ground to work properly.

5) Now you can power on the drive again, but be ready to shut off the power if the motor runs away at full speed. If the motor does not run away, proceed to step 6. If the motor does run away, power down the drive and set SW1-6 OFF. Make a note of which way you have SW1-6 set for the motor to not run away. Once you have this setting it should not need to change.

6) If the motor is not running away, make sure that you can turn the motor in both directions by adjusting potentiometer 4 in either direction.

7) Turn potentiometer 4 back to the middle so that the motor is not moving, and then power down the drive.

At this point you can set SW1-4 back to the OFF position to set the drive back to offset mode. Then reconnect the drive and motor to the machine.

Results: with option 2 Diagram
x axis with sw1-6 on; motor is not full speed, but is moving, POT4 will change direction, Green LED unless you adjust POT 4 as direction changes red LED (some flashing between green and red) will appear. Motor will not (w/o belt) stay still. No encoder or controller leads connected. Changing sw1-6 to off did not seen to change anything.

y axis with sw1-6 on; motor is not full speed, but is moving, POT4 will change direction, Green LED unless you adjust POT 4 as direction changes red LED (some flashing between green and red) will appear. Motor will not (w/o belt) stay still. No encoder or controller leads connected. Changing sw1-6 to off, adjust POT 4, 1 1/2 turns cw; and would almost stop motor. Motor stayed in motion.

I will try option 1 Diagram and post later.

Edit01: Attached is diagram as I understand it, option 02 in dotted or option 01 (OT-CNC, if possible please read, what I think you have written, to see if I have it correct) pin 9 to pin 11. It will be option 1 or 2; not both. I am willing to try this just want to verify the diagram. 1st I will try this with ebay drives, to test as per earlier (AMC suggested a way to test drive w/o controller, that will turn motors both direction by POT 4) described in earlier post. If any success here and I will report back, if this fails, the 25A8Ds are on the way. Thanks!!

Yes. Not both. If I read the docs correctly, the logic is switch dependent meaning you can turn the drive off when connecting pin 9 to 11 or turn it on. You could mount an estop there for your initial testing before you connect to mesa in case you get a runaway. I assume you have the motor pulleys removed and you're not driving the table at initial setup.