6ES5928-3UB21Siemens SIMATIC S5 CPU 928B
Buying 6ES5928-3UB21 from Flexa Systems
Buy the Siemens 6ES5928-3UB21 circuit board refurbished and in stock, with brand new units available on request, or send yours to Flexa Systems for repair. This board is rated for 24 VDC, so confirm that the control supply in the cabinet or rack it plugs into is delivering that voltage before fitting the replacement. Match the complete number, including the -3UB21 suffix, against the label on the board you are removing. Do not rely on appearance alone, because a board that looks similar may not be a drop-in substitute. Each refurbished 6ES5928-3UB21 is tested before it ships, carries a 2-year warranty and typically costs 30-60% less than new.
Repair option: component-level repair is available for this model — free diagnostics, a 2-year warranty, and a 5–30 business day turnaround. Repair typically costs 40–70% of a new unit, saving you 30–60%. Request a repair quote. Learn more about our Siemens repair and industrial circuit board repair.
6ES5928-3UB21 at a glance
| Part Number: | 6ES5928-3UB21 |
| Manufacturer: | Siemens |
| Voltage: | 24 VDC |
| Type: | CPU 928B CPU FOR S5-135U/155U |
6ES5928-3UB21 FAQ
What should I check on my current 6ES5928-3UB21 before swapping in the replacement?
Read the label on the installed board and confirm that the full part number and suffix match 6ES5928-3UB21 and that the rating is 24 VDC. Photograph or mark any cable and connector positions before you pull the old board so that everything goes back in the same place.
Should I order the 6ES5928-3UB21 refurbished or brand new?
Refurbished boards are in stock now, which suits a line that is down and needs this Siemens board back in service quickly. Brand new units are available on request if your plant requires unused spares. Both conditions have the same part number and 24 VDC rating.
Can I trade in a failed 6ES5928-3UB21 board?
Yes. Use the Trade-In button on this page to get a free evaluation of your board. Any credit is applied toward your purchase.
