Changer pile RTC

Like most FrSky radios the Tandem systems use the CR1220 lithium battery that are readily available. The RTC battery is located on the top area of main board that has the CPU and is partly covered by the RF board. Although it is partly covered there is adequate space between the two boards for removal and replacement.

  1. To replace RTC battery disconnect and remove the main battery.
  2. Remove four screws holding the case back.
  3. The 900m external antenna is located in the case handle and has a coax connection to the upper edge of the RF board. Lift the back of the case off but just enough that the case back can be rotated away for access to the RTC battery. Do not disconnect the 900m coax connection. Make sure the right and left sliders stay with the front part of the case.
  4. To keep the battery from popping out and getting loose in the system I use a 1/4″ X 1″ piece of masking tape stuck to the battery and use the extra part of the tape as a handle. Do not want the battery getting loose and injecting its remaining voltage into some random place in the system.
  5. Using a very small flat blade screwdriver with its metal shaft insulated with tape release the RTC battery holder battery retainer spring by pushing its center area over and away from the battery edge. The battery will popup.
  6. Using the masking tape remove the battery using caution that it does not come in contact with the main board or the RF board above it.
  7. Place the masking tape on the new battery and insert it in the battery holder with its outer edge under the molded retainers on the holder.
  8. Using the insulated screwdriver press down on the battery with the flat side of the blade on the side with the retainer spring until the spring snaps over the edge of the battery and it is retained in place. Remove the masking tape.
  9. Reassemble the system case and connect the main battery.

Power on the system and navigate to SYS/Date & Time. Set the date and time. Power cycle the system to test that the date and time is saved.

The voltage of the RTC battery can be viewed on the SYS/Battery screen. The RTC battery low voltage alert can turned off and on, on the SYS,/System Alerts screen.

Emplacement
CR1220