Scope of this technical record
Electronics supply, CUD1 boot and PMU display path for no-display and unstable-control cases.
Control electronics are connected to hazardous converter systems. Qualified isolation and verification are required before inspection.
Path boundary
This path starts with cabinet control supply and electronics input, then moves to internal auxiliary conversion, CUD1 boot state, PMU/interface path and downstream power-interface loading.
Use this path when
Use it when the PMU is dark, the drive resets, fault history is not reliable, or a suspected CUD1 replacement lacks supply and connector evidence.
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Used to verify that 6RA70 fault work should preserve the fault value and separate CUD1 / power-interface evidence from field and armature circuit evidence.
Used to confirm the 6RA70 architecture as a three-phase AC supplied DC converter for armature and field circuits, with hazardous service boundaries around power and control electronics.
Turn this record into a qualified service request
A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.
- Complete drive type code / MLFB or nameplate model
- Fault code, fault value and first event before reset
- When the event appears: power-up, enable, ramp, run, decel or stop
- Motor/cable connected or isolated during the symptom
- Visible board, option-card, module and connector identifiers
- Previous repair history, replacement parts and repeat-failure pattern