Troubleshooting Fanuc oi-mc FSSB alarm 926

[DanP_85]

Greetings. So I have a Chevalier FTC-1320v VMC that I bought about a year ago. Its about a 2005 vintage, BT30 VMC machine with Oi-Mc control and a rotating table (similar to a Brother R450x1). On the chevalier machine the table is the 4th axis.

I'm finally getting around to getting it setup. This weekend I was flushing the coolant sump with CimClean cleaner and then loading new coolant, and I got a black screen of death with Alarm 926, which is some problem in the FSSB communications. Screenshots below.

There is not a good fibre optics drawing with this machine but I think the fibre network goes from the PLC to the 4th axis servo amp then the SVPM last (XY and Z all being part of the single svpm box if I'm understanding correctly?).

I was able reboot the machine but had Alarm 5136: FSSB Number of Amps is Small, which means that the PLC sees less servo amplifiers than it expects. This went away after a few minutes and i was able to reset and home the machine. I've had the same fault repeat about 4-5 times, usually after about 10 min of run time, and the last few times it has rebooted just fine without the 5136 alarm.

The interesting thing is that if I'm reading the manual correctly, the first screenshot of alarms indicates it happened in the 3rd module in the fibre chain, but the others indicate 0 or the PLC itself.



1. Am I interpreting the codes correctly?
2. Does the other info on the screen mean anything helpful that might narrow down my search?
3. If so what are my next best things to check? The Fanuc book is a bit unhelpful, basically says its either the fiber cable, any module up or downstream of the error code location, a pulse coder power fault or a power supply in general....pretty much every piece of the machine.
4. I disconnected the two fibre cables (PLC to 4th) and checked them with flashlights, they seemed ok but is it worth replacing these? I know some fibre optic techs, could see if they could check them I guess for a lot of beers/money, there is a short one between the 4th and SVPM, but the main one is buried in the machine from the back cabinet to the control panel.

I have manuals and wiring diagrams for the machine, can share if it helps.

Parts Details:
Oi-MC A02B-0309-B502
Servo amplifier Bisv 20 A06B-6130-H002 E
SVPM3-15i/A part # A06B6134H303#A

Things to note:
All axis were stationary when it occurred
Spindle was off
Coolant pumps were either on or off
No program was running

 

[DanP_85]

Bit of an update but no progress really...bit more of a bump hoping some of the experts had a few more ideas at narrowing it down and some questions on parts numbers. I'm leaning towards it being the 4th axis SVM amplifier.

To date I've checked:

• Alarm history page (on two of the 926 alarms, Y-axis 364 or 463 occured 1 to 2sec prior)
• L1/L2/L3 system voltages, all 217 to 218VAC
• 24vdc power supply voltage =24.01vdc
• Cleaned all the optical cables and ports
• Tried to bypass the 4th axis amp.
• Good earth continuity from amplifiers to the cnc's earth bar, and earth bar to my 3phase distribution board.
• Checked SVM and SVMP alarm codes

The SVM does not show any alarms (no yellow LED). The SVMP also has no alarms on Status1/Status 2, except when in black screen of death status 1 is 24, but I think thats normal when the controller isn't fully booted?

I learned through fiddling that the optical cables are really really sensitive to contamination, this video on youtube explains it pretty well

Though plugging and unplugging them I must have made the contamination worse because the control wouldn't even boot at one point. I was able to get some cleaning supplies from a local electrical/data shop. The cleaning tape dispenser and sticks to clean the outlet are cheap. Its recommended you clean before plugging anything back in every time; a good practice for a greasy machine shop. Didn't solve my problem though.



The machine boots fully again after cleaning, but is stuck now with a 5136 alarm. I tried plugging the first optical cable straight into the SVMP, bypassing the servo amp for the 4th, but I still have the 5136 alarm. In this state, the machine will stay powered up indefinitely and not have a black screen of death 920/926 alarm. I'm not sure if this tells me anything though.



Possibly a question for Vancbiker or Angelw: once a 5136 alarm occurs (less amplifiers than expected per parameters), does the machine stop trying to communicate via fiber? E.g. after the 5136 occurs does the watchdog/health check stop happening? If it stops happening then that test tells me nothing, if the watchdog is still active it leads me to believe its either the 4th axis amp or the second fiber cable causing the 920/926 alarms.

Any other diagnostic input? I'd rather not start throwing parts at the machine without confirming a likely culprit.

Also: my axis control card is a A20B-330-0392/01A, from what I've read the 01A is the version number. There is an 02A on ebay, are these backwards compatible or do I need the same version? Similar question with the SVM, mine is a A06B-6130-H002 E, is the E a version number and does it matter?

 

[DanP_85]

Any help? Have I broken some unspoken rule?

This thread has a similar type of error but he got a lot more assistance: https://www.practicalmachinist.com/...hine-new-problems-spindle-error-codes.411601/ I'm kind of struggling to understand why.

BTW I ordered an axis card and the two optical cables, hopefully the version thing I mentioned earlier doesn't matter. I didnt want to just throw parts at it randomly but I guess I am. I ordered those items as it was cheaper than the small SVM amp...if the axis cards and optical cables don't fix it I'll know its the amp.

 

[Vancbiker]

Sorry, virtually no experience with the 0i controls. On earlier Fanuc controls one could boot into the IPL mode and set a smaller number of axes to step through them one at a time to try and identify the troubled unit. No idea if the 0i has a similar ability. IME the fiber optic system Fanuc uses is very robust. I've seen some seriously effed up ones still work fine. My gut feeling is a bad amp. With the fiber cable unplugged from the amp can you see light on one of the connections when the power is on? On the older fiber systems, the fiber is unidirectional. In other words one fiber receives data while the other sends. If the 0i is similar then one side of the drive connector should show some light and the other dark. The cable should show light on the opposite fiber.