The symptom: a bus fault that the basic test does not confirm
The customer reported a bus fault: the LEDs on the DFE32B option card stayed red. An initial basic test did not reveal any fault on the bus. In this kind of situation, it is tempting to declare the card OK and look elsewhere—at the risk of returning equipment to the customer that will fail again once reinstalled on the machine.
The test bench: real SEW + Siemens communication over Profinet
To complete the diagnosis, Yoann recreated the real operating conditions in the workshop: the SEW MDX61B drive and its DFE32B card, controlled by a Siemens S7-1200 PLC via the Profinet fieldbus. This required two configurations:
- the SEW drive, configured using its MOVITOOLS software;
- the Siemens PLC, programmed in TIA Portal.
This test bench allows functionality to be tested far beyond a simple check: the drive and the PLC can be observed actually exchanging data, in both directions.
The diagnosis: one-way communication
By analysing the exchanges on the bench, the fault became clear:
- from the drive to the PLC: OK;
- from the PLC to the drive: NOK.
The drive was communicating with the PLC, but the PLC could no longer send its commands to it. The DFE32B card was therefore faulty. Only a full test, with real communication, could prove it: a basic test would have let it pass.
Why this matters for your maintenance teams
A card incorrectly declared OK means a second downtime a few days later, another removal, and a loss of confidence in the repair. Testing under real conditions is the guarantee of a repair that lasts. It also makes it possible to put equipment back into service for the long term, rather than replacing it and turning it into electronic waste.
This case also illustrates our ability to make different brands work together on the same industrial fieldbus. Your lines often combine SEW drives, Siemens PLCs and other brands: our test benches adapt to this reality.
Is your drive or option card faulty?
SEW-EURODRIVE drives, fieldbus option cards, PLCs: we diagnose down to component level and test under real conditions, all brands. Discover our variable speed drive repair and industrial electronic board repair services.
Free diagnosis and quotation, 24-month warranty, emergencies handled within 24 hours: request your diagnosis or call 02 97 58 52 60.
Frequently asked questions
Why can a SEW DFE32B Profinet card pass a basic test while still being faulty?
In the case presented, communication worked in one direction, from the drive to the PLC, but no longer in the other, from the PLC to the drive. A basic test does not reveal this fault: the card must communicate with a PLC and the exchanges must be checked in both directions.
How does 2TECH test a SEW MDX61B drive fitted with a DFE32B card?
On a test bench that reproduces real conditions: the drive is programmed with MOVITOOLS, a Siemens S7-1200 PLC is programmed in TIA Portal, and the two communicate via the Profinet fieldbus. The exchanges are analysed in each direction to locate the fault.
What symptoms should suggest a fault on the DFE32B option card?
In this customer case, a bus fault reported by the machine and LEDs that remained red on the option card. This symptom is not enough to conclude: only a full test, with real communication with a PLC, can confirm that the card is the cause.
Does 2TECH repair other brands of drives, cards and PLCs?
Yes. We work on all brands, including installations that combine several brands on the same industrial fieldbus, such as SEW and Siemens here. Diagnosis and quotation are free, and our repairs are guaranteed for 24 months.
