4.2 Replacing the Drive Assembly


These are the instructions for replacing the Drive Assembly.


4.2 Replacing the Drive Assembly

In order to carry out the tasks outlined within this section, you will need to break the environmental seal of the radar sensor and expose various internal components. For this reason you need to remove the sensor from its mounting (as outlined earlier in this guide) and take it to a clean, dust free, anti-static work area.

The kit required to service the CTS-series radar sensors is available from Navtech Radar.

Please contact customer support with your radar model and serial number to obtain the correct kit.

Figure 1 - Contents

CAUTION: This kit contains high powered magnets in the Rotor Assembly. Please refer to the Health & Safety sheet regarding magnet safety -https://www.magnetexpert.com/health-and-safety-i934

Required Sub-Assemblies and Parts

1 x SUB0299 Dual 55 Assembly

1 x SUB0269 Motor board Assembly

1 x SUB0268 Rotor Assembly

1 x BOA0099 DD Retro-Fit Board

1 x WIR0094 Motor Cable

4 x SCR0094 M4x10 Skt Ctsk Screw

5 x SCR0067 M4x12 Skt Cap Screw

5 x SCR0063 M6x12 Skt Cap Screw

2 x SCR0162 M6x16 Skt Cap Screw


2.5mm hex key

3mm hex key

5mm hex key

10mm spanner

T20 Torx® key

Torque driver for hex and Torx keys

14mm spanner (for pressure gauge)

16mm spanner

Servisol® grease

Loctite® 243 - to be used with all screws except the Radome screws

Soft dry brush

Pressure test kit (Navtech order code: NAV0128)

Hand or foot pump with Schrader fitting

Anti-static surface and wrist strap

Latex (or equivalent) protective gloves

4.2.1 Open the Enclosure

  1. If the radar unit has not already been disconnected, isolate the power supply and then remove the power, data and earth connections.

  2. Using a 16mm spanner, remove the small breather valve located just to the left of the connectors. A replacement breather valve is supplied in the service kit.

  3. Using a pen, make a small mark across the side of the radome and the chassis to indicate the correct orientation.

  4. Using a T20 Torx® driver, loosen the six bolts that secure the radome to the chassis (replacement bolts and washers are supplied in the service kit).

  5. Once all bolts are equally slack, remove them all fully.

  6. You can now lift off the radome. You may need to gently twist the radome to break the seal with the o-ring.               

Figure 3
Figure 4

4.2.2 Remove the Upper Assembly

  1. Turn the rotating dish assembly in order to provide clear access to the small retaining bolts.

  2. Using a 3mm hex key (do not use ball ended drivers), loosen the four small retaining bolts and remove the fifth locking bolt. The bolts are secured with Loctite 243 and will be resistant to movement.

  3. When all bolts have been loosened off and the locking bolt completely released, rotate and carefully lift off the upper assembly from the turntable.

    Figure 5

    CARE POINT: Inspect the metal dish or plastic lens on the rotating assembly for dirt and debris. Clean any debris away using a soft dry brush.

4.2.3 Remove the Drive Assembly

  1. Carefully unclip and disconnect the multi coloured motor ribbon cable (A) from its edge connector on the main board. Note how the cable is routed so that the new motor cable can be routed in the same fashion on reassembly.  

    Figure 6


  2. Using a 5mm hex key (do not use a ball-ended driver) and a 10mm spanner to hold the pillars from loosening, undo and remove the five bolts that secure the motor assembly. These bolts can be discarded.
    NOTE: The bolts will be stiff to undo due to being assembled with Loctite 243 at the factory.
    CARE POINT: Check the 3 pillars have not been loosened.

  3. Carefully lift the complete drive assembly up slightly from the chassis to provide access to the encoder connection.

  4. Carefully un-clip and disconnect the encoder cable (B) from its edge connector on the main board. Ensure to grip on the latching pin at the top before pulling gently in a vertical motion.
    NOTE: Take care when removing this connector. If necessary, disconnect the adjacent Ethernet cable first to provide better access to the retaining clip of the encoder connector.

  5. You can now remove the old drive assembly from the chassis and return it to Navtech Radar (using the packaging supplied with the replacement unit).

    Figure 7


    Figure 8



  • Perform a full visual check of the interior of the chassis.

  • Ensure that no dirt or debris is present within the enclosure and pay particular attention to the plastic lens on the fixed optical stack in the radar base.

  • Clean any debris away using a soft dry brush.

4.2.4 Remove the Maxon Motor Board

  1. Remove the Maxon Motor Board from the main board in the base.

  2. Return the old motor board to Navtech Radar with the old drive assembly.

    Figure 9

4.2.5 Strip Down Retro-Fit Assembly to Component Parts

  • Observe caution when handling the magnets. Please refer to the Health & Safety sheet before handling: https://www.magnetexpert.com/health-and-safety-i934

  1. Remove the new Direct Drive Motor Assembly from the packaging and check for damage.

  2. Remove and discard the 3 bolts securing the Rotor Assembly.

  3. Place the Rotor Assembly back into the foam tray supplied with the replacement Direct Drive Assembly.

  4. Take care not to place the Rotor Assembly near any metal which may dislodge the magnets, or metal fragments which may get stuck to the magnets and cause abnormal behaviour.

  5. Contact Navtech if any magnet is dislodged, to ensure correct polarity.

  6. Remove and discard the 4 x M4 screws securing the Motor Board using a M2.5mm allen key.

  7. Check the Motor Board speed is set to 4Hz then place the Motor Board into the ESD protective bag.

    Figure 10

Switch 1

Switch 2

Switch 3

Switch 4

Speed (Hz)






CARE POINT: Take care when handling the Motor Board to avoid damage.

Figure 11

4.2.6 Daughter Board & Motor Cable Fitting 

  1. Fit Daughter Board (BOA0099) to the Digital Board ensuring fully inserted and correctly positioned with no pins overlapping.

  2. Check this is a tight fit, not loose.

    Figure 12


  3. Fit 1 x Motor Cable (WIR0094) to the Daughter Board ensuring it is fully inserted.

    Figure 13


    CARE POINT: If this is ever disconnected then check the crimps stay fully inserted in the connector.

4.2.7 Fitting the Drive Assembly


  • Check the lens at the top of the Beam Splitter is clean.

  • Ensure the 3 pillars are fully screwed down.

  • Take care not to trap the Motor Cable when fitting the Dual 55 Assembly or dislodge the Conical Baffle.

  1. Remove and discard the tape securing the encoder cable to the underside of the Dual 55 Assembly.

  2. Connect the Encoder Cable from the Drive Assembly (SUB0299) to the main board.

  3. If the old drive assembly had 2 spacers underneath the front 2 bolts, then these will need to be re-fitted with the Drive Assembly using 2 x M6x16mm Skt Cap Screws (SCR0162) with Loctite 243, then use 3 x M6x12mm Skt Cap Screws (SCR0063) with Loctite 243 on the 3 pillars.

  4. If there are no spacers under the old drive assembly, then use 5 x M6x12mm Skt Cap Screws (SCR0063) with Loctite 243 to secure the Drive Assembly with a 5mm hex allen key.

    Figure 14

4.2.8 Fitting the Motor Board

  1. Connect the other end of the Motor Cable to J4 on the Motor Board (SUB0269).
    CARE POINT: If this is ever disconnected then check the crimps stay fully inserted in the connector.

    Figure 15


  2. With the radar connections facing towards you, set the Motor Board into position on the 4 pillars of the Drive Assembly with the Motor Cable tucked inside the Casting and with the board speed dip switches set in the 9 o’clock position as shown below.

  3. Secure with 4 x M4x10mm Skt Ctsk Screws (SCR0094) with Loctite 243. Take care when tightening these 4 screws; they need to be nipped up but not overtightened using a 2.5mm hex bit, Torque=60±5cNm.

  • Ensure the 4 screws are not overtightened to avoid breaking the clamp ring.

  • Check the Motor Sub Assembly is secure to the 4 pillars with no free movement of the board.


Figure 16

4.2.9 Rotor Assembly Fitting


  • The Rotor is fitted with strong magnets and should not be handled in a dirty environment where it may pick up metallic debris at any time, either loose or in an assembly.

  • Check that the 2 x Flux Rings are aligned concentrically on reverse side.

  • Check each magnet is located correctly in it's pocket in the Rotor and has not been disturbed.

  • Observe caution when handling the magnets. Please refer to the Health & Safety sheet before handling: https://www.magnetexpert.com/health-and-safety-i934

  1.  Aligning the 2 dowel pins (circled in pink below), position 1 x Rotor Assembly (SUB0268) with the magnets facing down onto the Dual 55 Assembly.

    Figure 17

4.2.10 Re-fit the Rotating Assembly

  1. Set 1 x Rotating Assembly onto the dowels and secure with 5 x M4x12mm Skt Cap (SCR0067) with Loctite 243.

  2. Tighten in sequence as shown below. This is to ensure the rotor sits flat.

    Figure 18


  3. Check the rotating assembly spins freely with a visible gap between the motor board coil clamp and the rotor, with nothing touching.

    Figure 19

4.2.11 Replace the Radome

  1. Lower the Radome onto the body of the radar unit, ensuring that the o-ring remains fully within its recess.

  2. As you do so, align the pen marks for radome orientation and also ensure the bolt holes coincide with those in the chassis (rotating the radome once fitted is difficult).

  3. Insert the six new bolts and washers from the service kit and using a T20 Torx® driver, tighten the bolts to a torque of between 140 and 160 cNm.

    Figure 20

4.2.12 Pressure Test the Enclosure

Figure 21

NOTE: The power and data connector with its cap on, are hermetically sealed on this radar model and so if fitted will form a gas-tight seal.

  1. Insert the pressure test gauge into the hole vacated by the pressure plug and tighten it to form an airtight seal with the enclosure.

    Figure 22


  2. Attach a hand or foot pump to the Schrader valve of the pressure test gauge and pressurise the enclosure to approximately 1 psi.

  3. Remove the pump from the pressure test gauge and allow the gauge to settle.

  4. After 5 minutes check the gauge. The pressure should remain at or around 1 psi. If the pressure has dropped by more than 10 to 15%, then the test has failed and your options are to either locate and correct the cause of the leak or return the enclosure to Navtech Radar for a wet pressure test.
    IMPORTANT: Do not put a radar unit that has failed the dry pressure test back into service, as water ingress could damage the radar.

  5. If this dry pressure test is successful, remove the pressure test gauge and place the new breather valve, supplied in the service kit, into the hole. Use a 16mm spanner to lightly tighten to a torque of between 0.6 and 0.8Nm - do not over tighten.

    Figure 23


  6. Apply two new warranty stickers to bridge the join between the Radome and the chassis:

    Figure 24


  7. The radar unit is ready for operation and can be returned to its mounting position.

  8. To fully complete the service procedure, you need to register the service date within the radar sensor. Please see the section 3.2 - Setting the service date and checking vital signs for details.