How do I fix the firmware on my VOLT trainer?

If you are experiencing one of the following issues with your JetBlack VOLT EMS Smart Trainer update your firmware: • Your VOLT led is solid red • You are unable to connect to the VOLT • Your VOLT is not showing up on any platform or device

The following are the steps to resolve the issue

  1. Download the nRF Tool Box App from App Store or Google Play.

    App Store:
  2. Download the VOLT firmware to your phone.
  3. Open the Tool Box App and navigate to DFU (Device Firmware Upgrade)
  4. Connect to Device (possible list below) Note: Do not connect other named devices.
    • JBOOT (VOLT default setting)
    • DFU…. (VOLT default setting)
    • VOLT
  5. Select Firmware
  6. Update


Please ensure procedure completes before disconnecting. Your light will start flashing once the update is completed.

If you are still having issues locating the VOLT, please try LITE BLUE APP to find and locate your Bluetooth device.


If your VOLT still does not show up on either the NRF or LITE BLUE APP, the issue is with your hardware unit. Please return to your retailer for warranty support.

We apologise for any inconvenience. JetBlack are working hard to include this procedure as part of the next app update.