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Okuma VAC-III problems - 78 ALARM-P VAC start SPINDLE-1 1001FFFF

TenthsTool

Plastic
Joined
May 23, 2020
Hello all, I'm having problems with an old Okuma LNC8 VAC-III spindle drive. The alarm code shown on the monitor is 78 ALARM-P VAC start SPINDLE-1 1001FFFF and the LED on the drive itself shows # 16. I recently removed a parts catcher and disconnected the wiring harness, but hooked it back up after the problem showed up and adding it back did not fix it.

I am getting ~205V across all legs coming in and +5V, 0V, 12V, 24V on the OSP power supply (in the main rack) appear OK accept for the ISO24 which reads 0V, but I'm not sure if this is a cause or an effect of the 78 alarm. The fuse inside the PSC power supply (external power supply on the door) is OK. The 4 5A and 3 0.5A fuses on the "bottom" board of the VAC-III unit are OK. I reseated everything I could find on the VAC drive, flipped breakers, and jiggled contactors everywhere else. At the end of the day yesterday the machine booted up twice in a row with no problems. I went home and slept like a baby. Then when I returned to the shop, the problem came back again. Luckily, the forum has an emoji for my first post ... :angry:

I could not find a 78 alarm in my manual, rather than bothering the folks at Gosiger tomorrow morning I wanted to try my luck at bothering you guys (also hopefully save someone a headache in the future). Thanks in advance and thanks for countless other times you guys have helped me out!
 
For anyone experiencing this issue, the alarm is a communication error between the control and the spindle drive. It is either 1.) a problem with the fiber optic cable or 2.) a problem internal to the drive.

I checked the fiber optic cable (shine a light thru one end and you should see a crisp light out the other end) and didn't see any problems. Pointing towards the drive, I took mine to a local electronics repair shop and one day later I'm up and running. The repair shop found a few connections that needed re-soldered and by their determination it was "enough to keep it from running." Hope this helps!
 








 
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