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Heidenhain Controller
Safety · Intermediate · 30-120 minutes
HEIDENHAIN 231-A870 - A870 Brake test is not allowed
HEIDENHAIN alarm 231-A870 occurs when the TNC control system prevents brake testing due to safety interlocks or configuration issues. The alarm fires when drive ready signals are missing, safety doors are open, or brake assignment parameters are incorrect.
231-A870
HEIDENHAIN 231-A870 - A870 Brake test is not allowed
A870 Brake test is not allowed
This TNC 640 error relates to the motor brake system. The control has detected an issue with brake operation or testing.
Root Cause Summary
HEIDENHAIN alarm 231-A870 occurs when the TNC control system prevents brake testing due to safety interlocks or configuration issues. The alarm fires when drive ready signals are missing, safety doors are open, or brake assignment parameters are incorrect.
Safety
- Refer to Heidenhain service manual
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Check Drive Status Display
Navigate to MOD > Service > Drive Status and verify all servo drives show RDY status active.
Look for red indicators or fault symbols next to drive numbers
- 2
Verify 24V Supply to Drives
Check 24V DC supply voltage at drive terminals and ensure all enable signals are present at X1 connector.
Ensure machine is in safe state before checking electrical connections
- 3
Reset Drive System
Execute drive reset via MOD > Service > Drive Reset or cycle main power to reinitialize drive ready signals.
Wait 30 seconds after power cycle before attempting brake test
Call a technician if:
- ·PLC program modifications required
- ·Drive hardware replacement needed
- ·Safety system reconfiguration
Prevention
- Regularly test door switches during PM
- Verify brake assignments after parameter changes
- Monitor drive ready signals during startup
Common Mistakes
- Attempting brake test with doors open
- Incorrect brake output wiring
- Bypassing safety interlocks
- Wrong axis selected for brake test
Seeing Multiple Alarms?
Seeing another alarm with this one? Enter the code.
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Always verify with your machine manual or a certified technician before performing service procedures.