Fanuc 15mb w/ alpha drives - W axis overcurrent (8) questions

I don't think many of you will be able to put much input into this, but hopefully someone's had the same issue and can point to, or confirm, a reason for this alarm.



Kitamura h400 apc 1998 (fanuc 15mb) with alpha drives

Getting an 8 alarm on the drive randomly, with SV003 "W abnormal current in servo" and SV013 "W Improper v_ready off"

For those not familiar with the machine, the W axis controls the pallet change arm. It pushes/pulls pallets in and out (pallet stations are side by side)



Some quick backstory that might be useful:

Bought it used locally for cheap. They fought this issue. They replaced the drive, motor, and encoder cable in 2015, but that did not solve the issue (I can see it in alarm history)

Eventually they got fed up, it looks like it sat a year before they decided to sell it.



Now, we have also replaced the drive with a refurb off ebay, with no difference in when it happens. It is randomly. Occasionally happens during a pallet change, but I would say 70% of the time it happens with the drive in question not doing anything... Today, it happened while drilling a small hole.

It has not happened in weeks previous to now, we thought we fixed it, but it just came back a few minutes ago. When we were having issues with it before, it might happen once or twice a day, or might go a couple days without issue.


Motor maggers good.


Now here are my question(s)


I personally am suspecting the ADAX board and/or the axis card on that board (W is the 5th axis and it needed a 5/6 card). I suspect it because sometimes when this happens, if I touch some of the little honda cables coming out of the ADAX board, it will throw that alarm. Sometimes. If it doesn't full on alarm out with an overcurrent, I might hear the motor thump out there. But it is not 100%. I did it just a bit ago, Swear I heard it thump when touching the encoder cable, but could not get it to do it again after screwing with it some more.


Could that board be the culprit? When looking at the troubleshooting page in the servo manual, I have done everything but check waveform (it says to plug a check board A06B-6071-K290 which I don't have into JX5 to check waveform). The last toubleshooting information it has after checking waveform is this:

"(6) If still there is noise, a probable cause is a defective commandcable or a hardware failure in the CNC."

... Which brings me back to this ADAX board.

*OR* could it be the main CPU board?





Anyone ever see this? I have the machine running right now, it isn't alarming and it might not alarm the rest of the day, or week, or whatever. My boss is considering buying the board next time it happens.

Nothing yet, eh? I figured this thread would get buried, lol.


Some extra information, just in case someone has an idea over the weekend:

1: suspecting the ADAX board and/or cards on it, I took it out, cleaned contacts with isopropyl, and ran it in and out of the base board it plugs into several times, to kinda clean up the contact points. I did not take out the main cpu board because it has way too many wires and boards in it, and I don't feel like making a mistake and mess it up (parameters and such)

2: While they replaced the motor, drive, encoder cable, and motor cable, they did not replace the cable going from the ADAX board to the drive. If have another alarm, I will swap that cable with one from another drive, to see if it follows the cable. I don't think it is bad but on those occasions where I've wiggled wires plugged into the ADAX board, it was one of them that I'd touch and hear it thud and/or alarm out.


It didn't alarm out today.

Just replying to update:

I only got the alarm twice during the week (once during a *tool* change, that was annoying to fix)


Anyway, yesterday we decided to buy a board off ebay for 300 bucks. It came with the same axis cards as we already have, so we will kill 3 birds with one stone and hopefully that is all it will end up being.

I'll update when we figure it out (might take weeks to be "sure" it is fixed, if it fixes it at all)

Another update, and I have questions to any Fanuc tech who might know this answer (this should be easier than the actual problem I have)


We bought a new ADAX board with the daughter cards and installed it a few weeks ago. The new board worked right away, and we made parts over the following week. BUT it did not solve the problem.

I had went away on vacation the very next day, and I am told it ran without issue the whole week and a half. But the job that was on there completed, and it ended up sitting a couple days + the weekend.

When I came back and turned on the machine, it instantly gave the alarms. 4 times in a row. So I turned it off, pulled the ADAX board in and out a couple times, then put it back in, power on, problem solved. It ran for a couple more days before giving the issue again. And again, I pull out the board, put it back in, no problem for at least the rest of the day if not couple days.


Now, my question is as follows

I assume the next course of action would be to replace the "base board" that the boards all plug into. It looks like this:

FANUC 3 SLOT CHASSIS PLC MODULE RACK 15M-MCU12569-1R A2B-2-/2A | eBay


The question I have is, if I pull those boards out (PSU, PMC, MAIN CPU, ADAX, OPT1), will I lose parameters/ladder/etc? While I believe I have this machine backed up every way possible, the thought of re-installing the parameters and ladder makes me hesitate to do it.

I would leave all the cables plugged into the respective boards, so I'm not sure if they would technically lose battery power or not but there is no cable going from the PSU to any of the boards, so I am assuming the boards are supplied battery power through this board.

Does anyone know for sure? Any thoughts? Something?


Just want to make it clear, there's no regrets getting this machine. Even with this problem, it is more reliable than a few of the machines we have sitting on the floor, and holds tolerances better too. Its a good tight machine, only trying to solve this stupid ghost in the machine.

The battery that backs up the parameters is on the PSU board and supplies power through the bus on the rack to the MAIN board which has the RAM where parameters, programs, etc. are stored. That bus also powers optional RAM on the PMC board if present.

The MAIN board and PMC board have a capacitor on them that will maintain their respective RAM for a short period of time. I don't know a spec for how long, but it is not a lot. 5 minutes you are probably good, 10 minutes???? The 15 control is pretty old and capacitors lose capacity over time.

I'd go into this swap assuming I was going to lose CNC and PMC parameters, programs(including any macros), offsets, pitch comps. You will not lose the ladder. That is ROM based.

Vancbiker said:

The battery that backs up the parameters is on the PSU board and supplies power through the bus on the rack to the MAIN board which has the RAM where parameters, programs, etc. are stored. That bus also powers optional RAM on the PMC board if present.

The MAIN board and PMC board have a capacitor on them that will maintain their respective RAM for a short period of time. I don't know a spec for how long, but it is not a lot. 5 minutes you are probably good, 10 minutes???? The 15 control is pretty old and capacitors lose capacity over time.

I'd go into this swap assuming I was going to lose CNC and PMC parameters, programs(including any macros), offsets, pitch comps. You will not lose the ladder. That is ROM based.

Click to expand...

Thanks for the information. I finally got the board yesterday, and was gung-ho about replacing it this morning. I probably had the boards disconnected for about 15 minutes total (had a pesky screw and also had a hard time getting the damn fan plug to go in - big hands)

I did not lose any memory, so apparently the caps are not too worn out (1998 year machine, so "only" 20 year old 15 control)


It did not work however.

I hate the "well, next thing to replace is ____" method but I don't know if there is a better way beyond calling Fanuc to come out. But as my boss put it, they'll fix it, but probably swap every board in trying it and then charge full price for all of em.


So, could a failing PSU possibly cause this problem? It never happens on any other axis.

Could it be the PMC? The w axis is "PMC controlled" according to the manual and keep relay bits.

Could it be the main CPU?



(We have replaced W drive, ADAX boards + cards related to W, bus board, and the previous owner of the machine replaced the W motor, motor cable, and encoder cable.)

swap every board in trying it and then charge full price for all of em

That's not how the Cleveland techs work. They will have access to an very deep knowledge base, and will swap out anything related but, they will only charge you for the part that fixes the problem. 4 hour minimum at 160 per as I recall. They do have good phone support, you may want to start with that.

ifixcnc said:

swap every board in trying it and then charge full price for all of em

That's not how the Cleveland techs work. They will have access to an very deep knowledge base, and will swap out anything related but, they will only charge you for the part that fixes the problem. 4 hour minimum at 160 per as I recall. They do have good phone support, you may want to start with that.

Click to expand...

Fair enough. We did not call yet, might not as of this update.

So, we did swap the power supply for the cpu, that did not resolve it. We were going to buy the main CPU board next (a couple hundred dollars) but I decided to fudge around with the machine one more time.


I noted before that sometimes if I pushed on the wires on the ADAX board, it might alarm out. Sometimes you'd have to barely touch them, other times you'd push on it pretty hard. And sometimes, no amount of pushing would get it to alarm.

Similarly, but not as regularly, if I touched/pushed on some of the wires on the main cpu board, it would do the same.



And I believe I noted above, if I took out the adax board and shoved it back in, it would usually solve the issue for a day or 2.



Now, I think/hope/pray I figured it out.

Instead of a board being bad, It really does seem like a simple bad connection. Not with the wires going to the drives/encoders, but I do believe that the connection between the main CPU and the bus board was not good enough.

I got a can of CRC Quick drying electrical contact cleaner, sprayed all of the female sockets on the bus board, all of the male sockets on the cpu/adax/pmc/psu, and even a few of the daughter cards I was able to remove without losing information. I did these one at a time, and it really does seem like the problem went away completely when I did the cpu.

I had cleaned them up before but it was with isopropyl alcohol. Maybe this CRC stuff works a bit better than that.


I theorize that when I removed and shoved back in the ADAX board (which is adjacent to the main CPU), it wiggled the cpu connection enough to not cause any problems temporarily. Machine goes cold, connection strengh reduces over night, and bam, next morning more problems. I was chasing an issue with a board that didn't exist??

It has ONLY been 1 week. I might be jumping the gun. But I can't get it to alarm out or thump by wiggling anything anymore. I tried and tried. For days it turns on and runs without issue.

Is it really gonna end up being that stupid simple?

dandrummerman21 said:

Is it really gonna end up being that stupid simple?

Click to expand...

It usually is, the big problem is always finding out what is going on.

Best of luck! I spent weeks chasing an issue with my lathe not zero returning. Swapped boards, motors, encoders, cables....turns out a bad switch in the parts catcher was keeping the machine from activating some interlock that enabled a good chunk of the ladder logic, but there was no alarm. Jumpered the switch, boom entire machine works. After spending tons of time and money swapping axis drivers, motors, encoders, wires.....it was a $10 switch. Argh.

So, it has been one month since my "fix" post, and I am here to post an update.


And I know that once you start bragging about how you fixed something that made no sense, it will come back to rear its ugly head. If this problem starts to come back after writing this, I have nobody to blame but myself.



I have had the machine alarm out 0 times since pulling the main CPU and cleaning it well. Machine ran most weekdays, no issues. No issues after numerous long weekends. No issue last week starting it after I wasn't here for 3 days. Just no issues.

I don't know how rare of an issue this is, bad main cpu connection. I would imagine it could have caused a bunch of different issues, not just a drive overcurrent. I hope after writing this thread that it might help someone struggling with a seemingly "unfixable" machine.

I mean, the previous owners wrote off the machine after spending thousands. I don't know how much they paid for what they replaced, how much they paid the service tech, etc. I do not know if Fanuc themselves came out (doubtful). I do know they got a new way cover for the tune of 1800$ for it around the time they started struggling with it. And I know we bought this machine for not much more than the cost of said way cover.

Even after buying a few boards and a drive off ebay, we don't have much in it, and the machine has been a stout moneymaker since it has been on the floor. I'm wishing for another one (for me, having a sister machine that I can swap pallets with would be awesome)

Anyway, thanks for the help, thanks for letting me rant, and to anyone struggling with drive alarms that persist after replacing everything related to the alarm, give the main cpu a try.

I wanted to give a "final update" (I hope!!!!) to this.

So a few months after my last post in January, the machine started giving errors again! Was daily, about the same symptoms, would randomly happen maybe once a day, usually in the morning, sometimes halfway thru the day.

No amount of cleaning would fix it this time though. We ran it a few months further after this, replaced a few more things.



I am fairly certain I now know what it was.

During all the board removals, swapping, cleaning, etc, I am pretty sure that cards were swapped out in desperation. And some combination of swapping made the thing work.

It turns out that some of the SIF / A/D Converter cards (A20B-2901-0360) were tired. I probably managed to swap to one that worked (had several extras from buying used boards on ebay). The reason I now believe this to be the problem is that I had the W axis give a SV117 alarm (which was different than we were getting). The documentation for that alarms says replace the A/D card. So I swapped it with the X/Y card and the problem followed the card.

So we replaced that card with a NOS one on ebay and we have not had an alarm in the last few months as a result. No re-seating boards, no contact cleaner. Just swapped this stupid card out.


So the point is, apparently these cards get tired and don't immediately give an alarm that suggests they be replaced until they fail further.

Hopefully *this* post helps someone.

Thanks dandrummerman for this post. Im a service engineer in the uk working on the Toyoda range of machines. I have had a Fanuc 15M axis amp with alarm 8 on Z axis. I exchanged amp's but the fault stayed with the Z-axis. I swapped X and Z motor and the fault stayed with Z. After reading your post I backed up the S-ram (power up with Page up and Page down button held while powering up and with a RAM card in the memory slot) I removed the MAIN-C card and swapped the axis control cards (Right hand slots) re assembled and tested. Fault now on X-axis. Bought control card from Fanuc (£250) and fitted, Happy days. I only lost Z-axis home position but I had parked all axis at home position. Parameter 1815 bit 4 to a 1 happy days. Thank you for keeping the post updated. Cheers, Harvey PS. Fanuc had replaced one card 8 years ago I now find out.

Excellent. Glad this post managed to help at least one person! lol