Scope of this technical record
Control-electronics workflow for dead PMU, reset-loop or unstable CUD1 cases where fault-code routes are not yet reliable.
Qualified service personnel only. Verify safe state before internal electronics inspection or connector work.
Workflow goal
The goal is to recover enough electronics-supply and PMU evidence to decide whether the issue is cabinet supply, internal electronics conversion, CUD1 boot, PMU/interface connection, downstream loading or a broader retrofit decision.
Result package
The useful package includes PMU behavior, cabinet supply status, CUD1 boot evidence, PMU/interface connection photos, downstream power-interface loading evidence and a parameter backup if the unit boots intermittently.
Field record checklist
- PMU behavior
- Supply state
- CUD1 boot
- Interface cable
- Downstream loading
- Parameter backup
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.
Linked records
A no-display 6RA70 case belongs on an electronics-supply and CUD1 boot route. The question is whether line supply, auxiliary feed, internal electronics supply, downstream loading, PMU/interface connection, CUD1 control board or power-interface loading prevents a reliable boot. A fault-code workflow cannot begin until the control electronics are stable enough to report status.
Separates a no-display or reset-loop 6RA70 case into cabinet supply, electronics supply, CUD1 boot state, PMU/interface path, downstream loading and power-interface loading evidence.
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