So after the dust has settled a bit on a customer, let me tell you about their problems, relating to improper installation of a regenerative power supply and a third party repair of a motor. Get a call a few months ago for a regenerative style power supply. Talk to the customer a bit and they had a raft of F860 faults before the power supply finally gave up. F860 is a short, either in the drive, the motor power cable or the motor. They were worried about just putting in a power supply, and I was too, but they meggered out the motor and cable and everything looked ok. Power supply in and they started running just fine. For a month. Then the drive blows. At this point I hear the story of the third party repair of the motor, but they will not hear of sending the motor out to have it checked as it was done by a local shop that “they have good luck with”. So, we send them a drive. It will not start as it is getting a F860 constantly. We send them new cables, and tell them they should get the motor checked again. New cables are installed, they run about a day and then blow out the drive and power supply. So we send everything in for repair and eval, including the motor. For the motor, freshly “Repaired” we get…


– Physical condition: Fair condition, Output shaft has light grooved damage.
– Pre-repair assessment: Thermo check is within Bosch Rexroth specification, HiPot test passed,
Winding test passed, EMK test passed, brake test failed.
– Operational Test: Failed, Encoder give out 89 fault and 22 fault.
– Disassembled the motor for visual inspection and found that Front beairng is severely worn out,
Bearing cup race is worn, Encoder is severely worn out and contaminated with dust. Rear bearing
and brake are worn out. Brake is overheated. Brake resistor is missing. The cooling fan has been
modified, Instead of cooling fan blowing the cool air to the motor, it instead it is pulling the air out.

So the “repaired” motor needed – Replaced: Front and Rear bearings, Brake, Front flange, End shield, Encoder, Supporting disc, Shim, Rotary shaft lip, Shim ring, O-Rings, Brake pins, Brake
connector and resistor, Cooling fan.

The interesting thing is that this didn’t even fix the problem. We had one more iteration to go before noticing that this motor was of a date code that had extended windings which required a different end plate. That was listed per serial number and was only something the manufacturer of the motor would have had (along with the special extended plate).

End result, customer down 4 weeks because of a badly repaired motor. The money they saved on the first repair was pointless, as it had to come back in for repair.