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Fanuc Alpha Series control, need help with a few cable connections


Apr 23, 2011
19970 DE USA
Recently, I purchased a SuperMax2 (25"x16"x24") bed mill with Fanuc Alpha (red cap AC motor) Series controller. The machine had the 4 main modules removed and was close to scrapyard, the only wires cut were the light, inside the mill enclosure and auto oil pump. Some of the cables were not marked with a tag that matches how the modules are marked. This is the description of what I know about the cables not plugged in.

Cables (has colored wires; brown, green with white stripe, black & blue) marked (x, y, & z) going to the bottom (see pic below, of Servo Amplifier Module) of the Servo Amplifier Module. The Servo Amplifier Module is marked: UL, VL, UM, UN, WL, (GND) etc.

Cables marked (x, y, & z) going to the CNC AXIS PCB (in the electrical cabinet, this is on the right side), each cable is marked x, y or z, but the plug does not have any corresponding number matching what's on the CNC AXIS PCB module.

Cable market "CRT" see pic below. Looks to plug in the bottom of the CNC AXIS PCB module. But only numbers are marked on the module, and nothing looks correct.

Green cable, needs to "plug in" to the Spindle Amplifier Module, the other end of this cable goes to the "spindle position coder" (this is how it's spelled in manual) this I believe is belt driven from the spindle.

The JX1B (socket) on the Spindle Amplifier Module has cable W8 that needs to go to JX2B on the Servo Amplifier Module, reference the attached diagram, below. The Servo Amplifier Module has only these options: JX1B, JX1A, & JX5. What is the correct location?

The last, unmarked plug (the other end goes to the number & letter display part of the Main Operator Panel) that looks like it belongs on the CNC AXIS PCB module.

Many thanks, all suggestions warmly welcomed. Most pics were too large to attach, will try other options. Edit: see pics below!!
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I was here earlier and thought the same darn thing. Photbucket-photoshmuckit...

While I'm here... never heard of a Fanuc P12 Control. Googles as a Servo Motor. Is that named wrong, or is it some very old or specialty control for knee mill type machines?

I will try a different approach to get pics to work, thanks.​

Vancbiker, I tried to get the pic I have compressed the file, but .zip does not help. I have not had any luck getting a file small enough to post. I have posted here in the past, just not with this revised version, will try again.​

13engines, on the specification sheet, calls it P12; Fanuc, O-M series, red cap, AC motors.​

This diagram in the center shows on the Spindle Amp Mod JX1B go to JX2B using W8 as the wire #. If you look at the pic "Resized No JX2B" (this pic needs to open in its own window) the Spindle Amp Mod does not have that option.
Many thanks, the attached pic are a screenshot of the original pic, cropping until the file size worked. So no title across the top.

This is a pic of the question in 1st thread; "Cable market "CRT" see pic below. Looks to plug in the bottom of the CNC AXIS PCB module. But only numbers are marked on the module, and nothing looks correct."


The last pic of Servo Amplifier Module has this question; "Cables (has colored wires; brown, green with white stripe, black & blue) marked (x, y, & z) going to the bottom of the Servo Amplifier Module. The Servo Amplifier Module is marked: UL, VL, UM, UN, WL, (GND) etc. What color wire goes where? Do I start with the "x-axis", each cable has 4 wires? The Servo Amplifier Module has 2 rows of screws to attach wires.

Many thanks


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Vancbiker will likely have more and better things to say, but your diagram has pretty much everything there. Take your black, blue and brown wires and connect them all the same way following exactly how the diagram shows. Using the same color on each U, V and W group. The green and white wire is Ground. Note that the diagram on the connection cover is referring to the physical location of the connection terminals under the cover. There is a X,Y,Z correlation between the three plugs on the front of the 6079-H304 and the wires you connect underneath, and the three that connect to the axis card. As you can imagine, each pair of connections is physically connected to one of the three servo motors on the machine. Generally the connections are from top down or low number plug to higher number plug in an X Y Z sequence. You want to get this right or you could end up with a runaway on a non functioning axis.

I think that JX2B is a misprint and should be JX1A. A daisy chain just like the others.

I believe P12 is jut that. Page 12 of your manual. Page numbers in electrical manuals are very important, as are the numbers or letters typically running down the side margins.

I have 6079 servo amps on two of my machines. One Incremental OMC and an Absolute 18MC. I can double check things tomorrow when I get to the shop.

The CRT cable should connect to a Graphics card. At least it does on my OMC. Without a graphics card I'm not positive as to where it would go.

For a very thorough secondary reference you can always refer to a Fanuc OM 61393 Connection Manual (Hardware). Sometimes OM Maintenance Manuals are good too.

Edit: Can't spell. Changed/removed bits of info.
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For the servo power connections, wire color, (except for green or green/yellow or green/white which are always ground) is not standardized, it's up to the builder. You need to open a power connector at the motor and see what color is soldered to pin A. That will be your U wire. Pin B will be the V wire, and Pin C will be the W wire. Pin D will be ground (green with yellow or white). You can't mix them up. If you do the motor will try to run away a short distance then the control will alarm. L is your X axis motor. M is the Y axis, and N is your Z axis.

You need to post which model of 0 series control you have. There are A, B, C, D, F. There are differences in how the cables connect. The cable marked CRT does not plug into a servo board. Should plug into either the mother board or Memory board depending on control model.

13engines, Many thanks! I will cross the JX2B vs. JX1A off the list, thanks for you clarifying the cable plugs in to the JX1B location!​

Vancbiker, Many thanks for your help. How to tell which model (this is a 1995) of "O" series this is, the manual has "PLC B1 RO4" on the cover?​

I will see if there is an easy motor, to open the power connector (so not in the motor, look in the connector on the outside of the motor) to see "pin A" (will this be marked or otherwise obvious?) before connecting any of this group of wires (the cables are marked x, y & z).​

I have reviewed my manuals (it has PLC B1 RO4 on cover of electric manual), don't see any reference to a Model. The way I know O-M is on the front "Main Operator Panel". This is not flat screen, display on the top left, top right is "key pad" on right side.​

The cable that plugs in to the back of this "key pad", as mentioned in earlier sentence The cable described in this earlier question "The last, unmarked plug (the other end goes to the number & letter display part of the Main Operator Panel) that looks like it belongs on the CNC AXIS PCB module." This is all I know about this cable.​

As mentioned, earlier, the "spindle position coder" cable do not have a location.

This model has the fiber optical spindle device, not completely shore of the name, but know the location. The plan is to install last.

Many thanks!!
If 1995 then most likely a C or D. The mother board part number would allow one of us to determine the model. A and B models had a label on the metal frame of the motherboard that designated the model.

Vancbiker, Many thanks! Will try pic, but if not it looks to start A02B. Will be looking to find the answer to the question, what color is soldered to pin A.​


Many thanks!
Here are a couple pictures of my Supermax 3 OMC (1994-ish?) Does your Control look like this? Note this is connected as an Incremental machine, which I'm thinking your machine is too.

I just saw the new post with your part number. This here has the same part number, only one year older.
MAX 3 OMC Mem 50.jpgMAX 3 OMC Edge 50.jpg
When you go looking to identify the Servo Power wires that Vancbiker mentioned, you want to open or remove the connection on the motor that is closest to the middle of the motor. The one nearer the top will be the Encoder connection which you don't need to bother with. The only way to see which is A,B,C is to look carefully at the face of what will be I'm thinking a female connector. The letter labels are there. If you dismantle the Connector Housing, the letters will also be molded onto the Pin Retainer. Very small but they're there. If you don't have an Ohm Meter, opening the housing would be about the only way to assign the appropriate letter to the proper wire color. I would bet that if you identify the wires on one Servo that they would be consistent throughout.
That little black connector at the lower left of the Memory Board picture is the Digital Spindle or Optical Spindle Connection. Curious if your last unknown Spindle connection is this one.
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Vancbiker, Many thanks! Will try pic, but if not it looks to start A02B. Will be looking to find the answer to the question, what color is soldered to pin A.​

View attachment 381445

Many thanks!
Clearly shows 0-MC.

If the cable marked CRT goes to the display then it should connect to the MEM board at, IIRC, CX5 or similar. If I get a few minutes I’ll have a look at my connection diagram to verify.

13engines, Many thanks. The top pic has the Optical Spindle Connection in your pic is the same as mine. There is a small module for the fiber to plug in to the (don't have that in front of me now) cable.​

It looks like the "X" axis motor is available to see w/o taking anything off, but real bad with crud. I have Ohm meter, the motor looks too far to reach from outside the enclosure, so I need to be prepared.​

Vancbiker, I see the CRT needs to connect to CX5. I will be checking this before climbing in.​

Many thanks!!

Vancbiker & 13engines, many thanks! Using an Ohm meter this is what it says: A = Brown, B = Blue, C = Black & D = Green W white stripe on the X axis. I will wait for your thoughts, many thanks.​

There are 3 plugs marked, x axis, y axis & z axis, all look to plug in to the memory board (is this the correct name for that module, memory board pictured in​

13engines's thread?) but all the sockets are numbered. The diagram has letters that don't correspond with my cable markings.​

Vancbiker, CTR goes to CX5 or CCX4 (I only have the CCX4 option), so CCX4 because no other option?​

This pic is the optical I/O link, a plug marked "I/O Link" goes in to 1 side of this and fiber cable comes out of the other end, and goes to a socket as in 13engines's thread with pic of that connection. In this pic, you see the fiber plug in the upper right-hand corner that goes to the socket in 13engines's thread.RESIZEDOptical IO Link.png
No servo motor plugs plug into the Memory Board. They all go into the Axis Board (The one right behind the Memory Board.) This is also what your electrical drawing shows.

Look on the edge of the Axis Board and it is labeled just as you see it in your electrical drawing. You'll notice an inboard and outboard socket label designation. There is a fair chance that they will go in only in one area as some are going to be male and some female if my memory serves me. I have 4 axis on my machine so that is why you see two sets of four plugs. You'll end up with two empty sockets.

BTW - Vancbiker already explained to you how the Servo Power connections are connected once you found and assigned the colors. SEE POST #7

13engines, thanks!! I believe I am mixing the Memory Board & Axis Board terms, both of these make the Axis PCB and are in the same module, as you provided pics of, correct? Just need to be clear in my mind and try to get correct the 1st time around.​

I do see in your pic the CCX4 socket, with a plug in it, so CCX4 is correct.

Thank you for pointing out that all the information was available for the Servo Amplifier Module connection now the colors are known, ref: POST #7. I plan to work that in the morning.

Many thanks.
Sorry... I screwed that up a little.
From front to back the boards are:

1) Memory & Control (This has all the brains on it. Storage and EPROM etc.)
2) I/O (INPUT/OUTPUT - connects much of your ancillary stuff)
3) Axis Board (Servo stuff goes here)
4) Graphics (An Option you might not have. CRT goes here if you have it and connects on the bottom)
5) Power Supply (Mine is Type A) That cord coming out of the front of mine also connects to the CRT. 24VDC thingy.

Sorry about the earlier misguided guidance.

13engines, many thanks for the correct function and description of that module, I am getting my head around the names and locations of this new to me controller. I went to get eyes examined yesterday and some of the procedure made doing any close work (even with glasses) after the appointment impossible, today I am back to old glasses that still work ok, until the new come in, so did not do much yesterday.​

Today, I have connected the wires from each axis motor to the Spindle Amplifier Module, shown on the door of this module it has the position of each wire and at the end it appears there is no blank location. The attached pic shows a "BLACK" screw that seems to need the last "ground wire" to attach. Compare to the pic of door in post #5, this shows a blank (nothing printed) in the last location with 2 of the ground connections below, does this to mean attach at the base of the module, back away from this to where the module attaches to the electrical cabinet?

Many thanks!


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The picture is cropped so tight it makes it a little hard to get a handle on. But yes if you have only the one screw left and one green and white wire it looks like it would go there.

In an effort to avoid ground loops, there is a grounding scheme on these controls where you only want to frame ground everything in one place. I see on my machine that the grounds of the Power Supply, Spindle and Servo Amps are daisy chained together with I think a Frame Ground connection, and then a heavier wire heads off somewhere to ground the group as a whole.

As I said earlier, download the OMC Maintenance and also the Hardware (Connection) manuals. These contain a ton of information that will supplement what you got from the MTB. Honestly these manuals have almost too much information. Meaning it's easy to go down a rabbit hole trying to learn and understand it all. Still they contain veddy interesting stuff.

You can use the basic Microsoft Paint software to scale your images down without cropping. Check out the Canvas function.

13engines, thank you! I have a ground wire that is daisy-chained together to all major modules also. Thanks for the 2nd opinion about the last screw on servo amp module. I am running Linux 20. ? Cinnamon, desktop, I have tried several programs, but will look for the scale your images down without cropping option. I see what you mean about the OMC Maintenance and also the Hardware (Connection) manuals, this will take some time to get through.​


Edit: This is a big read, what is the best way to approach it? Is series O-M the same as O-Mate?
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