Scope of this technical record
No-display and unstable control-electronics route for SIMOREG 6RA70 cases where the PMU or CUD1 is not stable enough to support fault-code diagnosis.
Qualified personnel only. Isolate the converter and verify safe state before control electronics, PMU or power-interface inspection.
No display is not a fault-code problem yet
When the PMU is dark, flickering or resetting, the drive may not be able to provide reliable fault history. The first route is cabinet supply, electronics supply, internal auxiliary conversion, CUD1 boot state and PMU/interface path. Only after the controller is stable should F005, F030 or other stored faults be interpreted.
A no-display case can be a supply problem, a CUD1 problem, a PMU/interface issue or a downstream loading problem from the power-interface path. The evidence record should keep these possibilities separate.
No-display split
| Observed behavior | Likely route | Evidence to collect |
|---|---|---|
| Fully dark PMU | Electronics supply or PMU/interface path | Supply input, PMU seating, CUD1 state |
| Reset loop | Supply collapse or downstream loading | Rail behavior and connected board evidence |
| Partial boot or intermittent display | Connector, PMU or weak electronics supply | Heat/vibration timing and connector photos |
| Normal boot with stored F005/F030 | Return to field or armature route | Preserve fault value and operating state |
Field record checklist
- PMU behavior
- Cabinet supply state
- CUD1 boot evidence
- PMU cable/seating
- Power-interface loading
- Parameter backup if possible
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.
Diagnostic workflow
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