Hello everyone,

I’m working on a Hitachi Seiki TF-25 CNC machine from 1996 (using a Seicos A10 control system with an NEC computer) and need some help diagnosing an issue with the spindle drives. Both of our NEC spindle drivers (ASU30/40) display a persistent “7” in the top right-hand corner of each unit.

Based on what I’ve gathered from 09s-era service bulletins and technician recollections, this LED code “7” is not normal. Under proper operating conditions, these displays would either show a dynamic value related to the spindle speed, act as a parameter indicator, or remain off to signal normal operation. A fixed “7” seems to indicate that the drive isn’t receiving the proper encoder feedback or isn’t completing its parameter handshaking with the NC system—possibly falling back to a default mode or error state. BIOs battery did get changed so this may be the cause. A TC-25 Seicos A10L SC-200 service manual would help but I don't have one.

I have already investigated the wiring thoroughly, many times, but I’m still stuck with both drives showing the “7” code. Has anyone encountered this exact scenario on older Hitachi Seiki machines? Specifically, I’m looking for:

Insights on what the “7” LED really indicates in 90s-era documentation.

Any detailed service bulletins or maintenance procedures that address this issue.

Recommendations on calibration or troubleshooting steps that were common back then.

Any help, documentation scans, or firsthand experiences would be greatly appreciated.

Thanks in advance for your support!

Best regards, David